Earthquake – Focal beach balls

Picture by Associate Press: Earthquake in Japan 2011.

Stand in the place where you live

Now face North

Think about direction

Wonder why you haven’t before

Now stand in the place where you work

Now face West

Think about the place where you live

Wonder why you haven’t before

If you are confused check with the sun

Carry a compass to help you along

Your feet are going to be on the ground

Your head is there to move you around

From        “Stand” by R.E.M.

This is a bit of a follow up on Carl’s excellent “Earthquakes – What’s the fuzz?” post. I was asked to elaborate more on the “beach balls” that I mentioned in a response on that thread.

I’m not going to give you the details on that… I’m not capable of doing the math myself or quoting esoteric concepts about how to process it. I am however, going to give you enough geospatial background to understand what they are all about and what they mean.

The first thing I need to cover, mainly in order to bring every one up to speed… is the compass rose. The compass rose appears on many navigational charts and a method of calculating direction from one point to another. When coupled with an actual compass, you can find your way from one point on the chart to another.

The rose is noted in degrees from 000° to 359° (actually 359.99….) which is a full circle. North is 000°, due South is 180°. Many features having to do with the earth are discussed in the bearing that the feature lies in or has moved.

Image by GeoLurking: Compass rose.

Which brings us to:

Lineament n (often plural)

3. (Earth Sciences / Physical Geography) Geology any long natural feature on the surface of the earth, such as a fault, esp as revealed by aerial photography.

On Carl’s “Earthquakes – What’s the fuzz?” post, that stunning picture of the San Andreas is a Lineament, or a linear feature. It’s a surface manifestation of the thousands of years of slip along that section of the San Andreas. In some places, you can find creeks that have had their channels offset by several meters… in other words, they don’t line up across the fault. It has shifted that much since the creek bed was formed.

San Andreas fault.

Not all lineaments are formed this way, remember, a lineament is just an odd linear feature. In the New Madrid Seismic Zone (NMSZ) there are several lineaments that were un-explained until modern research revealed them for what they are. (well, at least to the point that we can talk intelligently about them) Crowley’s ridge is one of them.

Crowley’s ridge is a linear structure sitting right in the middle of the flood plain of the Mississippi river. It’s a raised structure made up of loess, which is wind blown silt.  A lot of loess deposits are ultimately of volcanic origin, being the fall-out of some of the larger eruptions that North America has had over the millennia. So… how is a 170 meter high ridge of silt able to exist in the middle the flood plain of one of the more powerful rivers on the planet? In all likelihood, it’s from uplift due to the mechanics of the NMSZ. (If you wonder what this has to do with volcanoes, the NMSZ has several emplaced plutonic structures scattered along its extent… those are “failed” volcanoes along the “failed” rift structure)

Now to bring this into something more on the subject. (that was all lead in)

Generally, when a quake occurs, it is along a fault plane that is oriented in relation to the stress on the rock.  In the case of the San Andreas, it’s from the westward moving North American plate and the northward moving Pacific plate (relative motions).  When the quakes occur, they usually are oriented along the trend of the fault. The focal solutions usually show a fault plane oriented on a line from the Northwest to the Southeast.

Faults are not two dimensional structures. Most are a diagonal break in the rock that angles down as you go deeper. This is called the “dip” of the fault. Dip angles that are less than 180° are normal faults, those that are angled greater than 180° are reverse faults. Which side the fault is measured from depends on which side is the headwall, or the part that rises relative to the other side. Those that principally slide past  one another without one side lifting, are transform faults. The dip angle is usually pretty close to vertical (near 180°)

This is all represented in a neat little graphical construct called a “Focal Mechanism.” A common name for them are beach balls because that’s what they looks like.

Here is one for a recent quake in California.

 

Image by GeoLurking. Focal Beach Ball, the name is really self evident.

For this graphic, the extensional part of the quake is shown by the shaded region.  Seismic stations in that area would have shown the “first motion” on the traces to be going up as the wave arrived. Stations in the unshaded quadrant would have seen the “first motion” as going down. The best way to read this, is to think of the two unshaded regions moving towards the middle of the ball, and the two shaded regions being pushed away from the ball. The orientation of it illustrated the fault orientation. In this case, the dip angle is 23° from vertical. The NP1 solution (mathematically derived) shows the fault plane to be oriented along a bearing of 11°. The alternate solution, NP2, shows 226° NP1 being the most likely explanation of how it happened. (Note, this is subject to correction since that is the best that I can find… but could be wrong)

Now… I mentioned lineaments earlier. Here’s why. A fault that is oriented at 11° is also oriented along 191° (11+180). If you draw a line along those two bearings from a point on a map, say where the epicenter is at, that would describe the fault plane as represented by the focal mechanism.

You can  explore this more at the USGS explanation of it here: http://earthquake.usgs.gov/learn/topics/beachball.php  or at http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/faults.html        .   For an authoritative discussion about it from an actual geologist, I recommend http://scienceblogs.com/highlyallochthonous/2009/12/5_focal_mechanisms.php

Now that I’ve covered that, a word about volcanic quakes. Magma forcing its way into a segment of rock usually will not generate “double couple” solutions, or if they are there, they will be either too small or too chaotic in order to pull this sort of data off of a lot of seismographs. Magmaintrusion causes most of the first motion traces to be upward as the overall volume increases and the rock splits apart. This means that pretty much all of the waves in all directions will be compressive waves. That was why that 1996 Bardabunga quake was so weird… the math and the motions pointed at no net volume change, and no double couple that matched something tectonic.

Remember, not all quakes will have a focal mechanism solution in the quake report, only the larger ones. This is mainly due to the large number of reporting stations that have to be used to derive it. Smaller quakes just don’t register on as many stations. Usually you will find the ‘beach balls’ in the technical details for the quake.

Well, I hope this helped. In order to get anything more detailed than this you’re gonna have to poke at a real geologist to pony up more info. This is just a layman’s understanding of it.

GEOLURKING

Edited in October 2014 to add a link to an awesome video explanation of beach balls:

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360 thoughts on “Earthquake – Focal beach balls

  1. Great post, Geolurking. As a geomorphologist and a glaciologist, the loess part really triggered me, I’m even doing OT just to read about it. Crowley’s ridge is a spectacular feature, no doubt about it. If a feature like that existed in my part of the world (Norway), I would have to explain it by 1) raised shallow marine deposits (e.g. glaciofluvial deposits) due to glacioisostatic rebound with subsequent erosion, or, 2) deep marine deposits such as silts and clays, again with subsequent erosion, leaving only the ridge behind. The loess I’m not too familar with, but such deposits can accumulate to huge features, like in China. The two options above do not exclude the other, as loess can accumulate on top of marine deposits. Erosion is clearly possible, with two large rivers that have shifted their course noticeably.

    The tectonic bit is not up my alley at all – but do the NMSZ coincide with the ridge? Are you familiar with any have papers that present uplift rates? With tectonic uplift and activity, the area would be prone to alot of landslides due to sensitive silts, and it indeed looks severly gullied.

    As for the loess, it might be of periglacial origin, with strong gusts bearing it down from the Laurentide ice sheet margin. Ash would contribute as well naturally – and could allow some dating by tephrachronology? Osl dating is also suitable for particles deposited by eolian processes.

    Aaaanyways, as I’m not familiar with e.g. the marine limit, the Holocene and Pleistocene sea levels, tectonic processes etc. in the area, these are just simple assumption. A stratigraphic view of the ridge would contribute alot.

    • The NMZ is pretty old, and considered to be a failed Rift system. Likely, it would have been the southern leg of a triple junction, the other two legs being represented by the Wabash seismic zone and another zone that extends to the north into Illinois.

      At the northern extend of the Mississippi embankment is a somewhat disordered graben feature where all three of these area meet.

      On the western side of the NMZ, the Commerce fault seems to represent a boundary fault. In my opinion, it may be related (though indirectly) to the earthquake swarms further south in Arkansas at Enola (≈ mid 80s) and Guy (ongoing). If you extending the Commerce fault it would pass right through this area.

      There are believed to be a few pluton emplacements scattered through the area, this is what I have been able to piece together. On here you can see the known faults.

      As for GPS data… the area is pretty slow.

      http://web.ics.purdue.edu/~ecalais/projects/noam/nmsz/ts/

      Crowley’s ridge is the feature on the flood plane that passes through BLMM, PIGT and ARPG

      • Laaate reply. Ok, good data. It doesn’t seem to coincide with the ridge though. Anyways, interesting topic, but I’ll leave it until someone gets me a stratigraphic view of the ridge 😉 Preferably with several different facies.

        Oh, and nice shoes!

        • Actually, the NMSZ does coincide with the ridge.

          The entire upper region of the Mississippi Embayment occupies the believed rift dimensions… and Crowley’s ridge runs down the middle of it.

          What makes Crowley’s ridge, a ridge, is up for discussion, but if you note that graphic.. the non shoe graphic, the green and green-dashed lines are additional faults of the complex.

          In general, the mechanics of the fault system have been described as a series of “step over” faults, with the compression vector being on a SW-NE line. (yes, compression, the rifting mechanism is no longer there)

          Anyway, an estimated cross section of the area.

          And a bit more description of my non-shoe plot. The hatched ovals are the emplaced plutons in the region.

        • An after thought…

          I guess it is possible that the ridge formed as a sort of bulldozer effect as the area is compressed.

    • Loess exists all up and down the region, I first became aware of it on a class field trip to Vicksburg Mississippi too many years ago.

      It figured prominently in sheltering the residents of the city during Grant’s siege. It was easily tunneled, and a vertical face carved into it would not flake off and fall. It made for great cave shelters. Pretty much the area is covered in it, and road cuts in it still maintain the face with only moderate erosion.

  2. @ All
    New bits ‘n’ bobs for Gems
    List of sundry environmental organisations as circulated at our lab, includes some earthquake related
    http://www.ags.org.uk/site/links/index.cfm
    Have fun looking at UK geology pick an area, zoom in and see whats there (solid only as yet)
    http://maps.bgs.ac.uk/geologyviewer/
    All UK boreholes plotted, some super detailed lithology, some rather ‘vague’ or use ‘localisms’, some confidential located but no details
    http://www.bgs.ac.uk/data/boreholescans/

    I’ll re-post in Gems

  3. Anyone checked the la Restinga webcams recently?

    The sea looks like it is full of ash (some of which could be due to the light) but the cam operator is having trouble focussing the webcam.

    • I’ve been watching off and on, but not for the last few. hard to see anything with the light failing. They usually play with the cam as the sun goes down to try and get the best pics.
      12 quakes registered so far today, 2 largest at 2.0 and 2.1.

  4. Avcan FB Comment by Avcan

    Anyway, I have to point out that the Moon influences in volcanoes, but not as the final variable, but there is more variable and so not always is the triggering factor, we must think that things are not black and white also are grey and like people, some Yes and others not…

    for example this commented this article of the National Gerográphic in this regard, which I leave for more or less fixed google translate… is quite interesting reading which come to a conclusion… the Moon is another factor that influences the eruptions of some volcanoes. (Henry)

    “There are linked to the lunar cycle volcanic eruptions?”

    Brian Handwerk
    For National Geographic News

    February 15, 2002

    The horrors unleashed by the recent eruption of the Mount of the Congo-Nyiragongo have once again demonstrated our difficult relationship with the fires that rabidly move below the surface of the Earth.

    In January, the tons of molten rock of the Nyiragongo entered the town of Goma, with the demolition of many of its neighborhoods and killing dozens of people. It was a hard reminder that, despite of the volcanoes have been sweeping areas populated throughout history, it still lacks the ability to accurately predict the deadly eruptions and save lives.

    If the prediction of eruptions is a confusing puzzle, Steve and Donna O volcanoes hunters ‘ O’Meara believe that it may have identified a key piece. The husband and wife team are investigating a connection pointed out some observers of the volcano from the earliest times, but none has been studied adequately, the role of the Moon affects the volcanic activity.

    The interest of the O’Meara in this theory lunar began by chance in 1996, while the duo was studying a volcano erupted in the field. Steve is an astronomer by profession, and was their experience in this field apparently unrelated that led him to a fateful discovery.

    During the compilation of detailed publications of his scientific observations, he began to notice a correlation between the increase in volcanic activity and the lunar cycles. Reviewing through piles of data he had collected over twenty years in the field, Steve reviewed the past eruptions and saw some of the same patterns. Additional research suggests that a lunar pattern was also apparent in some famous historical eruptions, such as Krakatoa in 1883.

    Other long-term observers of history had taken note of the possibility of such connection, but always as a note at the bottom, and provided that looking back on the eruptions that had already taken place. Nobody had given the complete field study, and no one had tried to use these patterns of dots as one of the tools to predict future volcanic eruptions.

    Stromboli, a volcanic access point

    With the support of the National Geographic Society, the husband and wife team set out to prove that same possibility in one of the volcanic hot spots of the Earth, the Summit of Stromboli Italy Aeolian Islands.

    Stromboli is one of the most active volcanoes on the planet. The mountain has been tireless in a State of almost continuous eruption for at least 2,000 years. In spite of large eruptions and lava flows are rare, smaller eruptions are very frequent and often launch droplets of lava on the rim of the crater.

    Earrings of Stromboli, which can be inhospitable. Visitors have to contend with the toxic gases, noxious fumes, and the shower of hot ash. While at the site of the team (consisting of Steve, Donna, and several research assistants # also suffered exceptionally brutal weather conditions in their field of the mountain top.) However, driven by their enthusiasm, they took to making observations of 24 hours a day, working in shifts of six hours. Despite the skepticism of some volcanologists, the Group was determined to put the lunar theory of proof.

    Despite living in Stromboli conditions left much to be desired, the climate was ideal for research because of continuously active eruptions and the occurrence of several lunar events. The moon came into some important phases during the time of the team in Stromboli. Over a period of 14 days of observations of the Moon reached the perigee # point in that its orbit is closer to the Earth) and also experienced a phase of full moon. The full moon is a point in which the Moon exerts a particularly large on Earth influence, as evidenced by high tides.

    The objective of the team was to determine if the highest peaks in activity of eruption occurred, and what is the relationship to the increased activity might have with the gr attraction

      • I just refer to Lurking on this matter and wish fervently that he one day will do the definite post on it… I have seen him doing t in several long comments with nice plots in them. But due to eventual copyright issues I can’t nick those and make them into a post.

  5. I am interested in building a very simple seismograph to be able to detect earthquakes.

    I would like to know from someone that has build something simple.
    Maybe I will first build something like a kid demonstration (probably slighty more elaborated). I was thinking suspending a pendul with a crayon or pen. My challenge here is understanding how to optimize design to increase sensitivy to the many earthquakes that here happen. Then, maybe at long term I would like to build something more complex but still not too much, desirably made of simple and easy to get materials (not too much electronics, because I really have no experience with it).

    Has anyone done any experiments?
    .

      • Not personally but someone on El Hierro suggested suspending a pair fo scissors in a jar; an EQ caused the jar to rattle. This might confirm that you are feeling an EQ (rather than just unwell) but not give a permanent record of the EQ, unless you video’d it.

      • No… but I had wanted to. Towards that end I usually kept the biggest most powerful magnet that passed through my possession.

        Right now I have two old AN/SPS-10 Magnetron magnets…. somewhere.

        They are fully capable of holding a person against a steel bulkhead when properly attached around the wrists arms and ankles, making it extraordinarily difficult to get free of. Today, that would be called hazing.

    • I have always thought about constructing an earthmicrophone.
      I got the idea when I built an earthdrum. And for those who have not heard an earthdrum while sleaping in a tent. Well, it sounds like an earthquake…

      What you build is a round ring, like on a drum, with tensioners. 4,5 meters wide (frequency), then you either get lucky and get fabric that is that wide, or you take out your Singer. Sow a skin for the drum (still the same concept), oil up the sturdy fabric to dampen it. You will probably have to oil it at least twice to get oilcloth. Because no air is supposed to be able to slip through. It takes a while to dry though.
      The comes the fun, you put it on the ring (on the ring you have put 8 1/2 inch welded steel rods), tension it so that it is evenly tensioned (not to hard, then it will loose those juicy ultralows). Then you drill 8 holes into the concrete floor in the garage. Lower down the rods into the flow after partially filling them with concrete, let harden.
      Now comes the electronics part.
      Either you use a tensionvibrationsmeter, a velocity meter, or a build a boom over it all and point a laser receiver/transmitter, then connect into a computer circuit board (arduino works), then you download some freeware… and you are good to go and record anything down to 0,05Hz (depending on quality of the actual giver).
      When you have an hour… speed it up about a hundred times, play it loudly out over the stereo. If you have large enough speakers your neighbours will never talk to you again 🙂

      And it would tell a lot. I would definitly build something like this if I lived on Iceland.
      Crude, efficient (large enough surface), cheap (comparatively), fun and informative..
      And yes, it would still work as an earthdrum. Whenever you feel like it you could go out into the garage with a rubber malet and drive IMO nuts… Not to talk about every dang dog in the neighbourhood. Your neighbours will worship you… *evil grin*

      This is at 1:10 ratio effecient compared to price of a pure electronics setup that does the same job.

      Mid priced version. Get yourself a couple of eighten inchers. Bolt them upside down to the floor. Connect em into the imput of a preamp. Build a passive filter that cuts at 12db/octace (fourth order filter) record on your computer, speed up, enjoy.

      The expensive stuff you can order online.

      This set up will give you audio only, it will not give direction. But who cares, you can feel the earth massage your intestines.

      • Thanks Carl, but mechanics and electronics are two areas which I am very poor at, something I wish to change.

        Tonight, I just hang a string some 2 meters from the roof and holding a free swinging weight with a ink pen. It works but not as nice I thought, only barely recording my jumping next to it. I wonder that it would only detect M 3.0 right under my feet, not any unfelt earthquakes.

        Also, since I dont have any motor running the paper, the ink just blots out a big blur after some 10 minutes, losing any chance of marking small vibrations.

        I will trying this week, building a wood block, with a horizontal wood beam, with a pen attached, to see if it is more sensitive. And I must improvise something to make the paper roll (a motor).

  6. After watching the picture of Japan at the headlines of this article…

    Poor people at Japan…

    Radiation at Fukushima is still equal as in the last months… The silent killer goes on…
    25120 nGy/h

    Real time measurements refreshed each 10 minutes
    http://www.bousai.ne.jp/eng/

    Translated lyrics.

    To all of you who want to enter the plant.
    We did not find who wants to enter, so we’re looking for people.

    Chorus:
    Let us enter the central entremoos, enter, enter into this paradise on earth,
    men who are in it are all men,
    enter into the plant and fall like flowers.

    If you want to try some excitement, please come to TEPCO.
    We have all the uranium and plutonium.
    We use subcontractors without problems.

    (chorus)

    All nuclear power advocates, coming to meet up near the reactor,
    no immediate danger to the body, wash in the shower, so good.

    (chorus)

    Nuclear energy is clean energy.
    Plutonium is not so scary.
    Its radioactivity only takes 24,000 years to disappear.

    (chorus)

    Japan should have nuclear energy for sustained energy.
    A little exposure is not problem drinking “Isojin”.

    We collected all spent nuclear fuel,
    packed in cans which is good,
    only 300 years must be left in pools of Rokkasho for cooling.

    (chorus)

    Despite the leaks, do not make noise.
    Although smoke, do not worry.
    While flying out the roof, all is well!
    That immediately cool it with salt water.

    (chorus)

    Although right now there is no danger,
    throw in the milk and vegetables.
    The government has said it will pay compensation.

    (chorus)

    Exhaustion of geiger counters for sale.
    You ought not to have those things.
    Radiation data are published here.
    Who believe it is saved.

    (chorus)

    • Well… there is some humor here… not at Japan’s plight, but at the idiocy of the activist groups in the US.

      After a gazillion years, the first new reactor permits were issued to Georgia Power. The plants may be online in a couple or three years. Immediately, lawsuits were filed to stop the plants.

      The reason? Because the design was allegedly similar to Fukishima and there was no provision to deal with a similar catastrophe.

      Hint… if you have a tsunami that can take out the plants in central Georgia, nuclear power is going to be the least of your concerns.

  7. There have been 12 earthquakes today in El Hierro 3 of them have been 1.4 one 1.5 one 1.6 one 2.00 and one 2.1.

    The strongest ones were at shallow depths of 10km and 11km.

        • 😯
          Yes, but shallow depth is perhaps 1-2 km and if you use the term in the wrong way like now (for 10 – 11 km depth! – i.e. 5-10 times that!), it could cause unnecessary fears (scaremongering). Pls. keep to the usages here to avoid this.

          And also: 2.0 and 2.1 are not strong at all, you won’t even feel them. – I know some about quakes having lived in Iceland for years!

          • These quakes in context are stronger than the ones recently that have happened in el hierro. I do not wish to scaremonger at all just observing from the wayside.

          • Stronger?
            There was a 3.3 just a couple of weeks ago.
            Judith, look at this ploy, especially on the fourth of febuary. There you see what the 3.3 did, compare that to todays 2.6.
            What you are seeing day after day is well within context, probabillity, depth, strength.

            Actually, I would say that it fits the modell almost to perfect. There will most likely be some strange outlayer soon, but that will also be withing statistical probability for the current pressure level.

            Even a 4M at let us say 7km would be withing probability range at El Hierro. And still would most likely not cause any harm.

            Judith, when a volcano is starting to wind down, or relax for a while. It is very easy to start looking for signs of reactivation. Most of us has had it now and then. I had it when Eyjafjallajökull shut down. Many had it back then, after a while people started instead to look at Katla “that just had to go off”, well Katla didn’t, it was Grimsvötn that did.

            El Hierro is a nice volcano, it gives signs that are rather clear of it’s pressure build up, I would say that we will know if it starts to get ready for something new. And those signs will not be small. Remember the very heavy 4M+s that happened without causing anything bad.
            So when you see all these quakes, just feel good, and know that it is quite normal and within what is expected. 🙂

            And do not think I have forgotten Bob, I am checking constantly to… and if I see anything new, I will write a post on it.

    • Judith,

      For a long time now, I have been on your side. Please keep posting. Your information is read and appreciated by me.

      I live in earthquake country, and I have been through some hair raisers. How you perceive an earthquake depends on the composition of the ground you stand on. Some 7M earthquakes can be felt strongly 100+ miles away. It has been an unusually long time since I have felt any shaking where I live, and that fact is alarming, the actually lack of activity. Anything out of the normal will cause people to be uneasy. So, I am with you. If there were no earthquakes and now there are, it is understandable that people will be uneasy. And, while I appreciate the attempt to calm you, and therefore protect you and all the Islanders, you are an adult and you are entitled to your feelings. That is not scaremongering. It is a report of what you or others are experiencing. And I appreciate that.

      I took an extreme interest in the report you stated of someone saying that it sounded like–what was that–trains or trucks running under their houses? I have experienced actually hearing an earthquake rumble in. It is an unforgettable experience. But the sound was followed immediately by the earthquake. To hear a sound and not have an earthquake would imply that whatever is making the sound is unimpeded. It is not so hard to imagine the possibilities, yet, to be able to actually hear the sound is unexplainable. Certainly, if I were living in a house where the ground spoke to me, I WOULD MOVE.

      Having said that, hundreds of microearthquakes can occur without ever feeling them, and can occur for decades without any damage. Yet, you pay attention, because all earthquakes mean something, period. What qualifies as an EQ swarm is debatable, but seismologists speak of EQ swarms preceding large quakes as precursors. Where I live those could be 2’s, but not necessarily meaning anything at all.

      I recall that the scientists on El Hierro identified a 4.0 quake as having, loosely quoting…”cracked the crust” which led to Bob. And, having watched all this for awhile, I can sympathize with your position of uneasiness because, although your language was not as succinct as would be liked, perhaps (not by me–I understood you), it does seem that the quakes are rising both in location and strength. It’s just that not much more can be said about them. They don’t seem to be going away, though, and with reports of sulfur smells, swinging glasses of water, rumbling noises, larger gas emissions in the water, and all that stuff…I’d stay alert. Bob is still plenty big enough, and he could crawl up the side wall, so to speak, unexpectedly. Stay tough, Judith. You’re doing good.

          • That would be Hekla. That one is much closer than the others. There has also been a lot of activity of microceisms at Hekla during the last 48 hours. About 30 percent more energy in the microseisms than in those at Katla everyone is excited about.
            I do not know what this is all about, but it started with an 0,3M mini quake without depth localized. More to the point, shes been misbehavin’ since last wees 0,7.

            But what it is I am really unsure about.
            I am really trying to make a plot the GPS movements of it to understand, but I sure as hork am no Lurking to put it mildly. And I am not going to post a map I have doodled arrows with a magic marker on in a post…

          • I guess all we can do is wait and watch. But meanwhile I need to sleep! Thanks for the information – I’m slowly working out what to look for on the charts. 🙂

    • And now for something… to ruminate on.

      The forces that drive tectonics are laboriously slow. Immense… but slow. About the only time it gets lively from a human perspective is when a volcano or other major stress relief event happens.

      As can be seen from side comments in this thread, the New Madrid Seismic Zone has it’s own unique thing going on. Today, there was a Mag 4.0.

      Last year, MRK and I were kicking around the sanity behind popping the levee along the Mississippi river and allowing the then flooding river to retake part of it’s flood plain. The idea was to ease the restrictions on the river and keep it from flooding (as bad) Cairo, Illinois. The issue that MRK and myself saw with this, was that the now mostly dried and highly fertile cropland would quickly return to a saturated condition.

      Saturated soil is much more heavy than not so saturated soil. And this area is directly on top of the NMSZ.

      After they popped the levee, there were a few tiny quakes up and down the zone, but nothing really alarming.

      Now take a look where the 4.0 was in relation to the area that was flooded.

      The river has since returned to it’s normal levels, but for a while, that entire region was under several meters of water last year.

      The detonation sacrificed 130,000 acres of rich farmland and about 100 homes in order to save the Illinois town of about 2,800 residents.

      “I hope this mission accomplishes what they wanted it to and the sun will shine again,” said Robert Jackson, whose family lost 1,500 acres to flooding.

      http://articles.nydailynews.com/2011-05-03/news/29523745_1_missouri-levee-illinois-town-blow-hole

      And a Youtube of one of the levee cutting blasts. (I think they did a total of three if I remember correctly)

      • Oh… and just so you know, that segment of the levee was designed to be blow up if it ever needed to be done. When it was built, they put piping put in place so that they could place charges at the needed locations.

    • Yes, that quake was on the morning news when I woke up. Supposedly it was felt here (I’m about 150 miles NW), but I certainly slept through it. Bobbi’s a bit closer I believe, so maybe she felt it. Bobbi, are you out there???

      Also seems there was an aftershock, a 2.4, about 7 hours later just 2 miles from the original. The New Madrid Seismic Zone is interesting, and Lurking knows a whole lot more about it than I do, but I’ve read recently that some researchers think it might be shutting down, and that dreaded devastating quake will never happen. That would be a good thing to say the least, as the 1811 & 1812 quakes were estimated to be close to 8’s.

      • Well, it’s about 750 million years old, and we have been looking at it for about 313 years (if you count the 1699 quake), so that’s about 0.0000417% of the time it has been in existence.

        In general, the “it’s shutting down” idea comes from the thought that isostatic rebound from the last glacial maximum won’t put any additional stress on it. Yet Montreal is still rising at about 4 to 8 mm/year… and the rest of the continent keeps shifting and adjusting also.

        http://en.wikipedia.org/wiki/Isostatic_rebound

        I don’t put much stock in the “Nothing to see here, move along” mindset, and I also don’t subscribe to the “OMG Were all gonna die!” scenarios.

        There is just too little observational data to support either camp.

        Curious how there has been an over all uptick in notable seismic activity from Virginia to the NMZ, to Guy AR, Oklahoma, and Texas… as well as Colorado. More so than just having better sensors can account for.

        My thought on the matter is that this is a result of additional stress pushing the continent ever westward. If that is the case, than the “It’s shutting down” crowd are dreadfully wrong, and following their idea of there not being a large quake threat… is dangerous.

        Nope.. always be as prepared for the worst case as you can be. In accordance with the idea of Murphy’s Law, you generally get what you don’t expect.

        I believe in the Black Swan.

        • Just since I love black swans.
          In the late seventies, early eighties a black swan was born in France. That gene was a dominant gene, and all of a sudden black swans started to sprout up all over Europe, them buggers do fly around. I saw my first in the Stockholm Archipelago in 2006. I usually use this as a piece “hork you, evolution exists, and happens under your ignorant ass”…

          And also to teach that any impossibility will sooner or later happen.

          • Heh… “evolution.”

            Issac Asimov has a short article that I read in one of his collections, “The Relativity of Wrong” if I remember correctly.

            In that article, he notes that the normal biosphere level of radiocactive C-14 is such that just from being a living entity on Earth, there is enough C-14 in our DNA, that about 10,000 C-14 to N-14 decay events occur every day, somewhere in a cell in our bodies, specifically in the DNA.

            By definition, a mutation is a change in the DNA of a cell.

            So… that means that there are about 10,000 mutations per day, somewhere in the cells in your body. Usually if the mutation is incompatible or harmful, the cell is attacked, killed and expelled.

            In some cases, it presents a beneficial trait and is kept around, or not noticed by the immune system. Occasionally, with enough of them, they may impart some benefit to the organism as a whole. In other cases, just cancer.

            I believe in creation, but I also believe that there is an evolutionary process at work. After all, I don’t question how God does what God does, I’m just happy that it all works as designed.

          • Is your love for the metaphorical or actual Black Swan? The actual Black Swan is the native swan here. They’re everywhere – making the old metaphor a little meaningless here.
            What type of swan was the French black? Was it a Cygnus atratus or a hybrid? Apparently there are lots of Cygnus atratus in the northern hemisphere that have bred from escaped captive populations. Presumably there has been some hybridisation with native northern hemisphere swans. Would make an impressive sight, though, black swan against white snow!

          • Kathryn, we do not have swans in the winter, they migrate the hork away from here Wise choice really. And, I am biologically challenged, so I just know about swans, and that swans generic come in white, and in black 🙂

          • @GeoLurking:
            Isaac Asimov was a most wise man. He said a lot that is well worth keeping track of.
            I am not a religious person really. But if I where I would like a God that was so powerfull that all the God needed to do was to set the base rule, hit run, and just let the program get on it with it, fully knowing that the best possible intelligent life would emerge down the line.

            Come to think about it, somewhere deep down I probably believe in something like that. My problem with religion stems out of to many people having made God into a small god that is just irritating. Probably due to them having problem with even imagining a medium-sized god.

            So, I am probably also some sort of creationist… But of a sort that would probably make half of all organised (and disorganised) churches start looking for firewood, oil, and a good ol’ torch.

  8. Problem I have is that Hekla is doing something unorthodox for being Hekla, and then we are talking about the world record holding volcano on the field of being unorthodox.
    Hekla is deflating. Magma is rapidly leaving the northeastern half of the volcano (Isakot/Burfell and Hestalda), it is still unclear if it is going south or not.
    This explains the microseisms recorded now at Mjoaskard, compression as one or more of the magmachambers get deflated.

      • It could actually equaly well be motion in the hypthetical subduction zone… Or something else like this.
        And note, I am note able to plot it out really… I can not really see it clear enough in my poor woolly head to get what is actually happening. As far as I know there are no fissures outside of Heklas fissure, except Litla Hekla.

      • And that would make an explosive mix if anything… If the Hekla lava met ordinary basalt from Iceland…
        But very very unlikely and has as far as anyone knows never happened in Heklas history.

          • If that had happened Katla would have blown like a bomb…
            The magmas of Hekla is totally incompatible with any other volcano on iceland and would result in the most disgusting and explosive magma possible…

            Let me say it clearly. Heklas magma is produced in a totally different process than any other magma on Iceland. It is produced by pressure melt through subduction. It is not hotspot magma at all.

          • @Tyler:
            2000, 1991, 1980, 1970.

            Only 2000 is a pure southern eruption. Up untill now the inflation has been unidirectional, and it has seemed as the eruption would be on the northwestern flank, or a 1947 eruption style. Most of the earthquakes has been around the 1947 area.

            So it could mean that the dyke emplacement running towards Burfell is emptyin out in preparation for a southerly eruption.
            So far we do not have a good enough image of what is happening.

  9. And before I go to bed to read a bit and sleep…

    I give you the runner up for the 2006 Texas Gubernatorial election. Not all politicins are bad, it is just that people tend to vote for the one with least brain.

  10. @ Denise & all – re: Missouri earthquake. I’ve had company visiting and just had a chance to somewhat catch up on the blog. No, I didn’t feel the earthquake – was busy shleeping! I have a friend whose cats woke her up though, jumping on her and crying. As to the researchers who think that the New Madrid is shutting down, I had also read that a while back. However, there are researchers who do not believe this at all. My theory is that they are all guessing and only time will tell.

    • Interesting about the cats. Mine are not too bright, though I did wake up with one of them purring away, so maybe he thinks earthquakes are fun. 🙂

      And I love your theory, you can’t go wrong with that!

  11. Avcan FB Comment by Avcan

    At the risk of being wrong, in the absence of more data than the comparison of the time of arrival of the wave to the seismographs of the other islands and the USGS data, this morning, have had what we understand as a new long period, typical event in stratovolcanoes and comienzarían to present at the El Hierro system, isolated nowThe eruptive tremor and form apparent. An LP or long period event, is a harmonic movement; i.e., the resonance in a musical note and their harmonics, low frequency which are not audible, but produced in volcanic conduits for magma fluids. These conduits, act as an organ pipes. In the seismogram, they are characterized by a slow weakening of the signal that produces, generating waves of various types. Attached a summary of the types of most characteristic form of LPs that can “play” to classify it and find out if it is indeed a LP (JR).

    http://www.geo.uni-jena.de/geophysik/inhalt/volcanology/tremor.pdf

    http://www.02.ign.es/ign/head/volcaSenalesDiasAnterioresHora.do?nombreFichero=CHIE_2012-02-22_01-02&estacion=CHIE&Anio=2012&Mes=02&Dia=22&tipo=1&hora=01-02

    http://www.02.ign.es/ign/head/volcaSenalesDiasAnterioresHora.do?nombreFichero=CHIE_2012-02-22_01-02&estacion=CHIE&Anio=2012&Mes=02&Dia=22&tipo=2&hora=01-02

  12. Err… Carl, you have mail.

    I’m apprehensive to post it myself, and can re-do the image for clarity if you like. The data was from the link you provided.

    I’m not quite sure what to make of it myself. Hekla is a pretty dynamic system.

  13. 1127962 22/02/2012 07:55:35 27.6593 -18.0581 10 2.6 mbLg SW EL PINAR.IHI

    Morning All,
    This the biggest in a while….

    • Ah, that was one dude that deserved a cake or two!
      In a way he is responsible for a very large part of my life.

      • Uploaded by Thespadecaller on 18 Feb 2008
        On July 26, 1956, the House of Representatives voted 373 to 9 to cite Pete Seeger and seven others (including playwright Arthur Miller) for contempt, as they failed to cooperate with House Un-American Activities Committee (HUAC) in their attempts to investigate alleged subversives and communists. Pete Seeger testified before the HUAC in 1955.
        In one of Pete’s darkest moments, when his personal freedom, his career, and his safety were in jeopardy, a flash of inspiration ignited this song. The song was stirred by a passage from Mikhail Sholokhov’s novel “And Quie Flows the Don”. Around the world the song traveled and in 1962 at a UNICEF concert in Germany, Marlene Dietrich, Academy Award-nominated German-born American actress, first performed the song in French, as “Qui peut dire ou vont les fleurs?” Shortly after she sang it in German. The song’s impact in Germany just after WWII was shattering. It’s universal message, “let there be peace in the world” did not get lost in its translation. To the contrary, the combination of the language, the setting, and the great lyrics has had a profound effect on people all around the world. May it have the same effect today and bring renewed awareness to all that hear it.

        • The darkest moment in US history. The House of Un-American Activities Committee is really such a dark period that it should be thought worldwide in schools. I always think about it when stupid politicians in europe starts to argue for limitations in freedoms and thoughts.

          • Yah.. really too bad several of the suspected were in fact tied with the KGB as evidenced by information from the Verona Project.

            http://en.wikipedia.org/wiki/Venona_project

            It doesn’t justify the public disclosure of the accused. McCarthy had wanted to keep the list of suspects private but was forced to disclose the information by those who did not wish to appear soft on communism.

            Sixty years later, we have one as a president.

          • But… thing is it was never illegal to be a comunist.
            KGB is one thing, but one should remember that most of those that stood accused was only normal people, artists, writers, and so on that on one time or another (most often pretty far back in time) been members of the US Communist Party.

        • After Flodden a series of laments were written for the great pipes of Scotland and the part known as the ‘Lilting’ was called The Flowers of the Forest. Words were written to it in 1756 by Jean Elliot which convey the same message of loss “The flowres o’ the forest are a weed awa'” (The flowers of the forest are all cut down). This great lament is still used at funerals – it was played at the Queen Mother’s funeral for instance. The message of ‘When will they ever learn’ goes back a long way.

  14. What do you think you guys about Hekla deflation?

    Just normal “breathing” or magma moving from one chamber to another?

    • I am going to write up a post about it. Let me just say that it is rather complex.
      But, I want to get it really right, so I am going to think about it for a day.
      On this one I want to feel really sure before opening my mouth since it is volcano that can potentially affect a lot of lives. Not least yours 🙂
      But it is coming!

  15. A curiousity…

    It has always been speculated that the southern coast of California USA is the region most likely to suffer earthquakes. According to a recent study that will be published in the next report, U.S. Geological Survey, there are between 10 and 15% probability that an earthquake measuring 8 or higher strike the U.S. coast from central Vancouver Island to border between the states of Washington and Oregon. The cities most at risk are Victoria (British Columbia) and Portland (Oregon). Previsón time: from 50 years hence.
    .
    This is the Juan de Fuca submersion zone which is a small tectonic plate submerging under the North American plate, which created the Cascade Mountain Range. These types of submerging zones are ripe for very large (mega-thrust) earthquakes similar to Japan.

      • I was talking about this the last year…
        I assume it is published now at U.S. Geological Survey report.
        A google with Juan de Fuca submersion zone could be interesting…
        But it´s good 10%-15% at 50 years…
        Good luck, sister…

        • I dont want to scaremonge you…
          But if the next reading is usefull for you or your next generations… It would be fine spend 10 minutes reading it…

          “We get a massive earthquake every 300 to 500 years around here, and we’re due. They’re super bad. When it comes, it’s a monster. A full-rip nine.’ ”

          By “full-rip nine” Corcoran means a mag­ni­tude-9.0 earthquake, the kind of massive off­shore temblor that triggered the tsunami that killed 28,050 people in Japan on March 11, 2011. Geologists call them megaquakes. Geo­logists also call the Northwest coast of North America—from Vancouver Island down to Northern California—one of the like­­liest next victims.

          “When that earthquake hits, it’s going to shake for a long time,” says Corcoran. “Three to five minutes or more. You’re going to feel lucky to survive. Then guess what. You rode out the quake? Congratulations. Now you have 15 minutes to get above 50 feet of ele­vation. Fifteen minutes. You’re elderly and not very mobile? Sorry. Your condition does not change the geologic facts. It’s called a tsu­nami. The water’s coming. It can’t be stopped.
          The Pacific Northwest is at the very top of that list.

          THE PROBLEM IS the Cascadia subduction zone, or CSZ. This is an enormous fault that parallels the West Coast for about 740 miles, from the Brooks Peninsula on Vancouver ­Island to Cape Mendocino in Northern California. It sits about 50 miles off the coast, ­marking the line where the North American plate meets the Juan de Fuca plate. The CSZ ends where the San Andreas Fault begins, about 100 miles north of San Francisco.

          The San Andreas you’re familiar with. It’s a transform fault—one characterized by ­lateral movement—where the Pacific plate grinds north past the North American plate. The creeping section of the San Andreas, south of the Bay Area, sheds its built-up strain in frequent small earthquakes, like a forest that burns so often it never has the chance to stock­pile fuel. The northern and southern ends of the fault aren’t moving, which leads geologists to believe they eventually will lurch, ­resulting in a quake as large as 8.1.

          2. “Largest recorded” means, in essence, dating back to 1880, when modern seismograph technology began to record the vibrations from earthquakes.

          The CSZ is a different beast. Up in the North­west, the plates don’t merely grind past each other. The heavier Juan de Fuca plate dives under (subducts) the lighter North American plate at a rate of 1.6 inches per year. Hence, a subduction zone. Transform faults like the San Andreas are capable of throwing off major quakes—up to 8.1—but not mega­quakes. Rule of thumb: the longer the fault rupture, the bigger the quake. Only sub­duc­tion zones have the length necessary to generate the mammoth 9.0’s.

          The CSZ is especially deceptive because it’s been inactive for all of recorded history.3 “Seismically quiet as Kansas,” says ­Robert Yeats, the éminence grise of West Coast seis­­mology and the author of Living with Earthquakes in the Pacific Northwest: A Survivor’s Guide. “Or so we thought.”

          Back in the 1970s and ’80s, Yeats and ­others attributed the CSZ’s quiescence to a kind of hyper-lubrication. The subduction zone must be so slippery, they thought, that the Juan de Fuca plate is sliding under the North American plate as if on a bed of axle grease.

          Then in 1979, John Adams, a New ­Zealand geologist working in Canada, noticed some­thing funny. Going over data from the ­Nat­ional Geodetic Survey, America’s surveying corps, Adams found that highways along the Washington and Oregon coast were gaining about one to two millimeters of ­elevation per year. His findings held all the ominous portent of a line from a Tommy Lee Jones disaster movie: Um, guys, why are all the roads rising?

          Other evidence compounded the ­concern. In 1986, Brian Atwater, a researcher at the USGS, was canoeing along the shore of Willapa Bay, north of the Oregon-­Washington state line, during a low tide. He noticed evidence of a “ghost forest,” old ­cedar stumps half-buried in the tidal ­marshes. The stumps sparked a memory; at a talk by USGS geologist Tom Ovenshine years earlier, Atwater had heard that spruce and willow thickets in Alaska’s Cook ­Inlet had dropped five feet during the 1964 Good Friday quake. Could the same thing have happened here? Tree-ring tests by colleagues confirmed that the Willapa Bay forest died in 1700. So did other buried estuary stumps along Washington’s southern coast. That date cor­res­ponded with historical ­accounts of a massive tsunami striking the ­islands of Japan in January 1700.

          This startling evidence made seis­­­­mologists sit up and take notice. Clearly, the Cascadia subduction zone had ruptured in a megaquake in 1700, down-dropping the Northwest coast several feet in elevation and unleashing a killer tsunami.

          As for the rising roads, well, think of it this way. Take a fishing rod and jam the tip up against a low garden wall. Now hold the rod at the butt and slowly push the tip into the wall. As tension builds, the rod will bow upward under the strain. That, in a nutshell, is what the North­west coast is doing.

          3. Which, in the Pacific Northwest, isn’t saying much. Indians have been here for 10,000 years, but written history arrived only in the early 19th century.

          “The new evidence meant that the Juan de Fuca plate wasn’t sliding easily ­under the North American plate,” says Yeats. “It meant that the two plates were completely locked.” Pressure has been building and building, for 311 years. If you are a geologist, at this point what runs through your mind is, Holy shit.

          Of course, the magic number could be 500 years, or (gulp) 244. For the past decade, Chris Goldfinger has been pulling samples from land­slide zones off the Oregon coast.4 By interpreting the cross-sections, he found a record of 19 full-rip nines in the past 10,000 years—a rate of about one every 500 years. He also dis­covered 22 CSZ quakes measuring 8.0 to 8.5. That means the CSZ has caused 41 major quakes in the past 10,000 years, or one every 244 years.

          So what we have now is a 740-mile ­section of the world’s most seismically active zone, the Ring of Fire, that has been building up elastic strain for 311 years. The North American plate, by some estimates, is now springloaded to leap more than 57 feet west and drop three to six feet in elevation at the coast. The CSZ always ruptures in one of two ways: as a kielbasa (along its entire length) or as one of numerous breakfast-link sausages (a single 200-mile segment). A breakfast link would set off an 8.0, limiting damage to a portion of the coast. The whole kielbasa would be a 9.0-plus that rocks the entire Northwest coast.

          “The amount of devastation is going to be unbelievable,” Rob Witter, a geologist with the USGS’s Alaska Science Center, told the Oregonian in 2009. “It may not happen in a person’s lifetime, but if it does, it’s going to be equivalent to a Katrina-like event.”

          Or, as Goldfinger puts it, “If it did happen, it can happen.”

          THIS IS HOW it will happen.

          Let’s pick a day: June 22, 2012. It’s a gorgeous Friday afternoon in the Pacific Northwest, 75 degrees and sunny. It’s been raining for weeks, and in Seattle the freeways are jammed with people fleeing the city to ­enjoy the rare sunshine. Same story in Portland. Out on the coast, the beach towns are thrumming with tourists. In Ocean Shores, Washington, teenagers race rental scooters up and down the town’s six-mile-long peninsula. Merchants are happy. The motels are nearly full. Down in bustling Seaside, Oregon, 75 miles away, shopkeepers are doing a snappy trade in ­T-shirts, towels, flip-flops, and sunscreen. Eight miles south in tony Cannon Beach, rest­aurants are booking tables for 7 p.m.

          4. During a subduction-zone earthquake, landslides occur on the ocean floor just as they do on dry land. Unlike dry-land slides, however, the most likely thing that can set off a seabed slide is an earthquake. So they make excellent markers of subduction-zone events.

          Officials in each town are aware of the CSZ megaquake-and-tsunami risk. They’ve all printed up evacuation-route maps. In Cannon Beach, they’ve even talked about building a new city hall that would double as a tsu­­­nami safe house. But nobody has ever had the money to build anything, other than installing tsunami-warning sirens.

          Not that there will be much warning. Even today, when it comes to earthquake prediction, the earth remains a poker ­player without a tell. “The best we can do is let people know how the shaking will spread once an earthquake starts,” says University of Washington geologist John Vidale, director of the Seattle-based Pacific Northwest Seismic Net­­­work. “Japan’s system is the best in the world. Within 30 seconds of the start of the March 11 earthquake, they broadcast a warning that it would be at least a magnitude 8.0.” No such system yet exists in the United States, though Vidale’s and other teams are working on one.

          “Let me tell you this,” Patrick Corcoran says as we stroll down Broadway, Seaside’s main drag. “There’s a shop a couple blocks up the street that sells T-shirts that say TSUNAMI EVACUATION PLAN: (1) GRAB BEER. (2) RUN LIKE HELL.”

          “And honestly,” he says, “that’s not a bad strategy.”

          MINUTE 0:00
          After 312 years, the Cascadia subduction zone can no longer contain the strain. It ruptures at a spot 55 miles west of Cannon Beach and quickly spreads along 700 miles of its 740-mile length. The North American plate slips anywhere from 45 to 57 feet to the southwest, sliding over the Juan de Fuca plate. It doesn’t happen instantly. A mass that large—remember, we’re talking about crust more than 50 miles deep—takes time to move. But upon its first lunge, the CSZ sends out a pres­sure wave, or P-wave, that travels through the earth’s crust at 13,000 miles per hour. It reaches the West Coast within ten seconds. That first P-wave, the earthquake’s leading edge, hits Ocean Shores, Cannon Beach, and Seaside. Thirty seconds later it reaches Port­land; in 50 seconds, it hits Seattle. At the Uni­versity of Washington’s Seis­mology Lab in Seattle, the seismometers jump. Geologists read the data and declare the earthquake a 9.1. It’s the full rip.

          The first few seconds feel like any other strong earthquake: jarring. “The pressure wave is like a jackhammer, rat-tat-tat-tat-tat,” explains Goldfinger, who happened to be outside Tokyo—at a geology conference to discuss the Sumatra earthquake—during the March 11 Sendai quake.

          The sound is majestic and awesome. In his book A Dangerous Place, author Marc Reisner wrote of his experience in San Francisco during the 1989 Loma Prieta earthquake: “What I remember most vividly is the grinding, the unearthly noise of great surfaces and structures grating together.” Chris Goldfinger recalled the sound of leaves rattling on trees. In Japanese houses, the sound was an unrelenting clatter of metal and glass.

          In the offices, apartments, and high-rise condos of Seattle and Portland, uncertainty creeps into half a million heads: Freeze or flee? In videos shot during the Japanese mega­quake, the overwhelming emotion on display isn’t panic or raw fear. It’s focused anxiety and strategic calculation. They are trying to figure out what to do.

          “People in buildings die in an earthquake one of two ways,” Corcoran says. “Either the building pancakes on top of them, or they run outside and a gargoyle falls off and hits them on the head. You need to know: Is your building a pancake or a gargoyle?”

          Instinct and old memories kick in. Many people duck and cover under a strong table. (Actually not the worst plan.) Others recall their mothers telling them to jump into the bathtub. (Wrong natural disaster! The bathtub’s for tornadoes.) Out on the roads, traffic slows to a halt, like a scene in one of those movies where invading aliens power down the planet.5 Some drivers get out and crouch next to their cars. Others stand and spectate. By and large, people remain calm.

          Except, that is, on Seattle’s Alaskan Way Viaduct. The elevated double-decker express­­way running along Elliott Bay begins to rock with the first P-wave. For more than two ­dec­ades, seismic engineers have warned that the Viaduct, built in the 1950s, will collapse in a major quake.6 Work on a $3.1 billion tunnel to replace it started in 2008, but the project has been delayed by political wrangling and soil problems. Now the Viaduct turns into a two-story demolition derby as people make desperate bids to reach the nearest off-ramp before the thing buckles. In the coming minutes, some sections will pancake, while ­others will topple completely. Drivers will be crushed ­beneath tons of concrete.

          Two hundred miles south, in the ­trinket shops of Seaside, merchandise hops off the shelves. At the Purple Pelican, glass ­seahorses, swans, and custom-painted wine­glasses crash to the floor. Half-drained beer pints dance off the bar at Pudgy’s Broiler. On the Seaside Carousel, fathers pull their daughters off painted horses and leap from the turn­table. Everybody knows it’s an earthquake. Nobody knows yet that it’s the big one.

          Meanwhile, 50 miles offshore, the ­movement of the North American plate displaces a massive volume of seawater. A standing wave just a few feet tall appears at the surface, then splits in two. One half heads west toward ­Japan at a speed approaching 450 miles an hour. It will reach Honshu, the main island, in ten hours. The other half heads east. It will hit the coasts of Oregon, Washington, and Vancouver Island in 20 minutes.

          MINUTE 1:00
          After the earthquake’s initial pressure wave, there’s a short lull. Then the S-waves arrive. These shear waves travel more slowly than the pres­sure wave, but they’re longer-lasting. A shear wave is like the wave that runs down a garden hose when you whip it. “It’s the S-waves that ­really do the damage,” says Gold­finger. “It feels like you’re on a boat. Every­thing turns fluid.” People start feeling dizzy. Some drop and hug the ground.

          The Pacific Northwest Seismic Network flashes an earthquake alert to first responders, government officials, and media outlets. The network’s instruments indicate that this is a full subduction-zone event, not a short fault rupture. “Expect shaking to continue for up to five minutes,” the alert says. “Heavy after­shocks will follow.”

          5. A study of Japanese drivers during a 2003 earthquake found that 90 percent had slowed to a stop within about ten seconds of the start of the earthquake.
          6. The Viaduct is a near carbon copy of the Bay Area’s infamous Cypress Structure, a one-mile stretch of the Nimitz Freeway that pancaked during the Loma Prieta earthquake, killing 42 motorists.

          In Seattle and Portland, the strong shaking begins to induce liquefaction,7 a process in which the sandy soil that portions of both cities are built on turns into a thick, slurry-like liquid. Parts of Portland rest atop sediment laid down by the Willamette River, and Seattle’s water­front sits on tidal flats overtopped by loose fill. In a quake, this unconsolidated fill loses its ability to support heavy structures. Wide cracks open in the streets. Sections of Seattle’s waterfront collapse. Liquefied soil pushes against the city’s retaining seawall, which has been weakened by gribbles.8

          On the Oregon and Washington coasts, the S-waves turn the landscape into a rolling sea. Tourists struggle to stay on their feet. Older buildings shift off their foundations. In Seaside, the 1924 bridge that carries Broadway across the Necanicum River can’t handle this dance. It twists, buckles, and collapses.

          MINUTE 2:00
          People start checking their watches. Nobody can believe an earthquake could keep going this long. For that they can blame the unique features of the CSZ.

          “Because there’s so much sediment on it, the CSZ is very smooth,” says Goldfinger. “Once it gets going, there are no ­irreg­ularities on its surface to stop it. If there’s no reason for it to stop, it’ll just keep going until it dissipates all 300-odd years of elastic strain.”

          Japan’s March 11 quake lasted more than five minutes. That’s longer than it takes a pot of coffee to brew. And that’s not good.

          “Most modern buildings weren’t designed to withstand three to four minutes of shaking,” says Peter Yanev. One of the leading seismic-engineering con­sul­tants, Yanev has investigated more than a 100 quakes around the world. “Almost none of the buildings in Seattle were designed for a megaquake.”

          Most unreinforced-masonry buildings9 in Portland and Seattle can survive a 45-­second quake, like the magnitude-6.8 Nisqually quake that hit Seattle in 2001. But the longer they’re shaken, the weaker the structures be­come. “The difference between 40 seconds and four minutes is like the difference between a head-on collision at four miles an hour versus 40,” says Yanev.

          7. About liquefaction: Sandy soils are held together by friction. But when you add water (the ground under Seattle and Portland is typically saturated at the end of a rainy Pacific Northwest spring) and shake, the bonds of friction break. The most famous example occurred during the Loma Prieta quake, when the ground beneath San Francisco’s Marina District turned to slop.
          8. That’s right, gribbles: flea-size isopods that eat wood softened up by salt water. They’ve been munching away at Seattle’s Elliott Bay seawall for decades. Each gribble has four mouths, a healthy appetite, and a symbiotic partnership with a bacterium that breaks down creosote.
          9. These buildings, with load-bearing walls made of brick or masonry, were typical in the early 1900s. They tend to collapse like the proverbial ton of bricks. California banned the construction technique as early as 1933 and required existing structures to undergo seismic retrofitting in the 1970s. In Seattle, about one-third of all unreinforced-masonry buildings have been retrofitted.

          Buildings begin to shake apart at the two-minute mark. Bricks rain onto side­­­walks. In house base­ments, hot-water heaters topple and rupture natural-gas pipes. Fires flare. In some communities, fire crews can’t respond because the earthquake has warped ­garage-­door frames. If they can get out, it’s a crapshoot as to whether they’ll have enough ­water pressure to fight the fire, because the earthquake has ruptured water lines.10

          Along Seattle’s waterfront, fire isn’t the problem. By minute two, piers begin to collapse. Ye Olde Curiosity Shop and Ivar’s Acres of Clams, two fixtures of the waterfront, slump into the bay. Power lines snap across the Northwest. There are no active nuclear facilities in the area, but along the Columbia River, high-voltage transmission lines connected to the river’s hydroelectric dams sway and topple into the river. Power grids across the West experience dramatic drops in supply.

          In Portland, a city famous for its bridges, the spans begin to buckle. The Marquam Bridge carries Interstate 5 over the Willamette River. In 1995, engineers installed shock ­absorbers and restraint cables throughout the structure as part of a seismic retrofit. As a result, it remains upright. The Fremont Bridge, which holds Interstate 405, was built in 1973. It topples into the Willamette. Along U.S. High­way 101, the coast’s main north-south corridor, dozens of bridges go down.

          In Seaside and Cannon Beach, lifeguards blow their whistles and stagger down the shore­line to call people in from the water. They know what’s coming. In Ocean Shores, there are no lifeguards. Most tourists stay put.

          MINUTE 3:00
          As the shaking continues, the northern ­Pacific coastline sinks. The elastic strain that caused roads to rise slowly over 312 years is being released in a matter of minutes. The coast drops—whump—five feet in elevation.

          There are more than 900 modern high-rise buildings in Vancouver, Seattle, and Port­­land. More than half were ­constructed before 1997, when most urban design codes were up­dated to reflect the possibility of a CSZ mega­quake. In downtown Seattle, there are reports of glass-and-steel ­office buildings buckling. This is hard to ­believe: weren’t they designed to flex and roll with an earthquake? Well, yes. But not this kind of earthquake. Most modern 20-to-40-story buildings are designed to survive nearby crustal earthquakes but not large subduction-zone events. Crustal earth­quakes send out high-frequency waves; subduction-zone quakes send out low-­frequency waves over longer distances. In some parts of Seattle, those waves react to Seattle’s soft soil like sound waves hitting a bullhorn. Along the waterfront, Harbor ­Island, and the Du­wam­ish Valley, ground motion will be two to five times as violent, and last twice as long, as it would at a comparable site on bedrock. In those areas, some buildings will collapse.

          The Space Needle is not collapsing. In fact, it may be the safest building in town. With its tripod legs, inner steel core, and massive under­­ground foundation, the Needle was built to survive 100-mph winds and a 9.0 earthquake. But low-frequency seismic waves have sent the Needle into a side-to-side whip like a car’s antenna. Now 78 visitors trapped in the top house stagger to walls and girders like storm-tossed sailors. Some splay out flat on the floor. The early stages of seasickness rumble in their guts. One ­woman recalls the spec­tacular view she enjoyed a mere three minutes ago and thinks, Boy, it’s a long 600 feet down.

          MINUTE 5:00
          Five minutes and 17 seconds after it began, the earthquake stops. The University of ­Wash­ington Seismology Lab tags it as the largest in the region’s recorded history. Globally, it ranks as the third-largest ever recorded by modern seismic instruments.

          10. In terms of fire, Seattle’s actually in better shape than most other cities, having spent $197 million in 2004 to quake-­harden its fire units. The SFD’s firehouse doors all open. The department has pumps and mile-long hoses to draw water ­directly from Puget Sound, Lake Washington, or any of nine reservoirs.

          The worst is over for Seattle and Portland. But in the beach towns, the countdown has begun. A tsunami that will inundate the coast­line is now about 35 miles offshore. It will reach dry land in a little more than 15 minutes. There are 7,500 people in the inun­dation zone in Ocean Shores. Seaside: 15,000. Cannon Beach: 7,800.

          Take the advice on the T-shirt. Grab beer. Run like hell.

          MINUTE 6:00
          The beach at Seaside is one of the glories of the Oregon coast. It’s flat, wide, vanilla-gray, and gorgeous. The lifeguards continue to herd swimmers and sunbathers away, but some are unconvinced. They don’t hear the tsunami sirens, or, having been through tests of the sirens in the past, ignore them.11 “This is no joke,” one tells a visitor. “You need to move. Now.” Move where? people ask. “Walk up Broadway,” the lifeguard says, “and don’t stop until you’re at the top of a hill!”

          The walk to Broadway takes three minutes. At this point the beachgoers are faced with a life-or-death decision. A crowd has formed at the doors to the Wyndham resort, an eight-story beachside hotel-and-condo complex. People are shouting and pushing their way through the doors, calling out for family members.

          Hard data has never been more valuable to these people. “Is it tall enough?” one person wonders aloud. “Will it stand?” another asks. The Wyndham’s windows are all shat­tered, but otherwise it looks structurally sound. It’s a long half-mile trek to high ground, with two bridges to cross. Rumors ricochet around the crowd: The bridge is down! No, it’s standing! Both pieces of information are true. There are seven critical bridges in Seaside. Some have survived the earthquake, some haven’t. The manager of the Wyndham appeals for calm. He’s old enough to recall the Who concert, Cincinnati, 1980, the killing crush of crowds and doors. He makes an appeal: Those who can walk should walk—Wyndham staff are already leading guests to high ground.

          “How far is it?” someone asks. “Half a mile,” the manager says. “Oh, Lord, I’d never make it,” says an elderly woman in a pink T-shirt. “I can’t walk that far.”

          For the beachgoers, two precious minutes are wasted mulling over the best strategy. A general cul­ling takes place. The firm and the fleet decide to keep walking. The ­elderly, the broken-down, the obese, the calculating, and the stubborn file into the Wyndham. ­Nobody has told them that the city­wide power ­outage has knocked the ele­vators out of commission. The crowd slowly trudges up eight flights of stairs. Strong men and women, strangers, band ­together in teams to carry the ­elderly and disabled up to the roof.

          11. In Japanese coastal towns, that’s exactly what happened in March. A tsunami alarm a few months earlier had sent locals scurrying for high ground. The water came in like a lamb, less than a meter high.

          A parade of stunned hu­man­ity files up ­Broad­way. Beach­goers who came away without their shoes now find the sidewalks littered with broken glass. They wrap their feet in T-shirts until they reach the Old Crab gift shop. There, one guy starts dumping armloads of flip-flops onto the sidewalk. “If your feet are bleeding, I have sandals!” he yells. “Please keep moving!”

          Earthquake debris has made driving impossible. Still, some people try. They honk their horns and attempt to maneuver through the crowds. Eventually they abandon their cars and walk.

          MINUTE 8:00
          The first wave is about 25 miles offshore. It slows as it reaches shallower depths but loses little of its power. The water along the coast begins to recede.

          In the major fishing harbors, a panicked exodus is under way. During the quake, boat owners recalled that tsunamis pass peacefully under vessels on the open ocean. They also remembered images of con­tainer ships perched atop four-story buildings in Sendai. Now they’re motoring all-out for open water. In Westport, Washington, a charter-fishing port directly south of Ocean Shores, dozens of vessels parade out of Grays Harbor. Fifty miles south, in ­Astoria, commercial fishing trawlers try to outrace the tsunami by heading up the ­Columbia River. They aren’t aware that a dam upriver has been damaged by the quake and is in ­imminent danger of breach.

          In subduction-zone quakenamis like the one that hit Sumatra in 2004, tourists are ­often the most clueless about what to do. In Sea­side, Broadway has become a parade of hurting-but-helping humanity, all heading east. Except … there’s one solitary figure weav­ing his way west. Toward the ocean. He’s kind of a dirtbag. No shirt, just an old swim­suit and huaraches, rock­­ing the white-dude dreads. Under his arm is a surfboard.

          One of the retreating lifeguards spots him. “Dude!” he calls out. “Don’t do it!”

          The surfer waves to the lifeguard and continues walking. Three days later they’ll find pieces of his board. His body will never be found.12

          12. Crazy as it seems, he won’t be the only one on the beach. With every tsunami warning, there’s always a small contingent of mixed nuts who drift down to watch the action and form a flash mob of Darwin Award nominees. At any rate, it’s physically impossible to surf a tsunami. Often called tidal waves, they aren’t “waves” at all. There is no face, no pipe, no curl. A tsunami is more like a storm surge. Common waves are created by wind energy. Tsunamis are created by the massive displacement of water, and terrifying Japanese woodblock prints notwithstanding, they don’t break like wind waves. They come ashore more like enormous high tides, with a low, inches-high leading edge backed by a steadily rising onrush of water. A 40-foot-high tsunami does not come ashore as a 40-foot-high wave. It steadily builds to that height with each successive pulse.

          MINUTE 13:00
          In Ocean Shores, which is built on a ­sandspit six miles long and three miles wide, high ground is miles away. Most locals have jumped into their cars, making their way slowly north on Point Brown Avenue. Lique­faction has chop­ped up the road, though. Only four-wheel-drive trucks and SUVs can get past the sloppy sand breaks. A few good Samaritans encourage others to hop in the backs of their flatbeds. Others blow past.

          In Cannon Beach, a power outage prevents town officials from broadcasting a tsunami warning. A city planner runs down to Haystack Rock, the town’s iconic landmark, with a whistle. He blows it wildly and yells at two dozen out-of-towners, who seem mesmerized by the receding tide and the bare seafloor. A few listen and follow him to the ­Ecola Creek bridge. But it has collapsed, creat­ing a pinch point. For years the town had discussed the possibility of retro­­­fitting the bridge. City officials wanted to build a new $3 million structure strong enough to withstand a tsunami, but nobody could ever come up with the funds.13

          MINUTE 17:00
          The crowds in Seaside continue up Broadway, crossing Highway 101, filing past the Chamber of Commerce and Broadway School. ­Finally, at Wahanna Road, a half-mile from the beach, the road begins to climb. At a look­out point, somebody passes a pair of binoculars around. The tide has gone out. And then suddenly it rushes back in.

          At Oregon State University’s O.H. Hinsdale Wave Research Laboratory, one of the world’s leading tsunami-research centers, wave hydro­­­logists have run sophisticated ­simu­lations of a CSZ-generated tsunami hitting Seaside, Cannon Beach, and other coastal towns. The findings do not suggest sticking around. “A lot depends on wave speed,” says Solomon Yim, director of the lab. “We found that in some blocks of densely packed houses, the first line of houses took the brunt and the second line was shielded.” The specifics of the tests haven’t been released to the public for fear of causing an upheaval in the local real estate market. “If your building was one that did not survive the simulated tsunami,” says Yim, “it would be … not so good for the resale value, you see.”

          MINUTE 18:00
          The leading edge of the tsunami hits the beach at Seaside. From the roof of the ­Wyndham, hundreds of people watch and record the ­water crashing ashore and flowing up Broadway. It comes in like a tide moving at flash-flood speed. Just a trickle at first, but within seconds it’s knee-high and then lapping at windows.

          By the time it neared shore, the pulse of ­water had slowed to about 30 miles per hour. On dry land, it moves inland at a speed of 11 mph. To outpace the tsunami, you’d have to run at least a 5:30 mile.

          The Wyndham and its neighbor, the five-story Shilo Inn, act like a nozzle. The water, black and powerful, jets through the opening between them: Broadway. Stragglers try to run, but the flow sweeps their feet from ­under them. Some hold on to lampposts. The ­water pushes wood, metal, and glass into them. The surge is strong enough to bend two-inch metal pipes.

          13. “They’re debating about whether they should build a $7 million bridge,” Corcoran says. “You don’t need a $7 million bridge high enough and strong enough to withstand the quake and the tsunami! You need a $1 million bridge strong enough to survive the earthquake, so people can cross it to escape the tsunami. However it’s built, it’s not going to survive the tsunami.”

          One- and two-story buildings groan. The water is reaching their rooflines and twisting their foundations. Some begin to lift and float up Broadway.

          “Seals!” someone shouts. True. There are seals swimming up Broadway alongside the bob­­bing SUVs. The 75-year-old Seaside Aquar­­ium, a several-story wooden building, did not survive the initial earthquake. Two of its harbor seals were crushed by falling debris. Two others were killed by the onrushing ­tsu­nami. The survivors now swim around the drowned town, con­fused by the water’s darkness, its oily taste and smell.

          The water keeps rising. It has overtaken the third floor of the Shilo Inn.

          MINUTE 19:00
          In Cannon Beach, the tsunami swallows up half of Haystack Rock and rushes up to the steps of City Hall. In Ocean Shores, anybody who hasn’t gotten out yet won’t. A few holdouts take refuge in another Shilo Inn,14 at four stories the tallest building in town. It’s not tall enough, as its staff have warned those who stay behind. The ocean has now entirely overtaken Ocean Shores.

          In Seaside, the crowd atop the Wyndham watches in horror as the water overtops the Shilo Inn across the street. People on roof­­tops leap into the water and attempt to swim to the Wyndham. But tsunami ­water is thick with sediment, wood, metal, and glass. It’s dif­ficult to move in. Gas fumes from broken lines make it hard to breathe. Many who try to swim drown. Those who cling to floating objects have a better chance of survival.

          MINUTE 21:00
          People in Seattle and Portland—those who have power and whose cellular networks are still functioning—watch live footage of the tsu­nami on their smartphones, shot by news helicopters. They wonder if it will hit the cities.

          It probably won’t. To reach Portland, the tsunami would have to muscle its way up 75 miles of the Columbia River and hang a hard right at the Willamette River. Seattle is similarly protected by the topography of Puget Sound. The tsunami will likely slosh up the sides of the Strait of Juan de Fuca and ­expend its residual energy on the western shore of rural, sparsely populated Whidbey Island.

          14. I’m not picking on the Shilo Inn company, which has 40 convenient locations in 10 western states. They just happen to site some of their hotels on prime oceanfront property. Those beachside resorts are big enough to lure panicked tsunami evacuees but often not tall enough to provide refuge from the flood. Guests would be evacuated.

          There could be a strange mini-tsunami effect in Puget Sound, however. Hydrologists call it a seiche. It’s like what happens when you kick a dog’s water bowl. The water sloshes back and forth in slowly diminishing waves. A handful of people who wander down to shore to watch the arrival of the tsunami will get sucked into the sound.

          MINUTE 60:00
          Secondary tsunami pulses batter the coast. They’ll continue for eight to ten hours.

          Survivors in Ocean Shores, Seaside, and Can­non Beach won’t get their towns back for days or weeks. Over the next month, more than 2,000 aftershocks will hit. Eighty-three of those will be big enough to be felt. Five will be above magnitude 7.0.

          The Northwest coastline’s elevation has drop­ped three to five feet. Normal high tides will now be flooding houses, hotels, and streets twice a day. In Ocean Shores, the situation is especially dire. Prior to the mega­quake, the highest point on the sandbar pen­insula was 14 feet in elevation. Now it’s nine. The lobby of the Shilo Inn, now a wrecked shell, is lower than sea level.

          Among disaster-relief experts, the ­calam­ities of the past decade have forced the realization of a truism: first responders are victims; victims are first responders. In other words, firefighters, police, military, and medi­­­cal workers are among those killed and injured in the disaster. And civilian victims (the able-bodied, at least) become de facto first responders.

          President Obama makes unsuccessful ­attempts to reach Oregon governor John Kitz­haber and Washington governor Christine Gregoire. A massive surge of traffic has crashed the Verizon, AT&T, and T-Mobile networks across the Northwest. But, having witnessed FEMA’s dismal performance after Hurricane Katrina and during the Gulf of Mexico oil spill, nobody is counting on the federal cavalry to come to the rescue. The Red Cross and other groups show up within hours. But in the year 2012, most disaster recovery is DIY.

          That’s especially true along the coast, where each town has been islandized. Highway 101 has been snipped into a hundred pieces. Nearly all bridges are down. State, county, and town officials quickly set up staging areas, but there’s very little top-down coordination. Food, shelter, medical care, and fuel are the immediate priorities. Hospitals are overwhelmed. Local social networks come into play. In Seaside and Cannon Beach, city officials work with fishermen and hunters, who have boats and ATVs. Air National Guard helicopters ferry the injured from coastal towns to hospitals in Richland, Washington; Bend, Oregon; and Salt Lake City.

          The Newport, Oregon, Walmart becomes one of the coast’s critical staging points for both food and material. As they did ­during Hurricane Katrina, Walmart executives in Benton­ville, Arkansas, get word to their store managers: Do whatever it takes to help your communities. Autonomy is yours. The company’s distribution network begins moving food, medicine, and building supplies to Oak­land and Long Beach, California, where they will be loaded onto chartered container ships and sent to Newport. From there, a mos­quito fleet of private boats moves the goods the final miles to affected communities. Other stores—Safeway, Home Depot, and Costco—follow Walmart’s lead. The U.S. Navy stations a floating fuel dock in Newport to keep the flotilla moving.

          EPILOGUE
          Six months after the megaquake and tsunami, the official death toll stands at 7,241. More than 3,200 were killed in or around Seattle, Portland, and Vancouver. Many died when older houses collapsed. Others were killed by falling objects or died in fires. A num­ber succumbed to heart attacks, and 679 were killed by the tsunami.

          That’s far fewer than the tens of thousands who died in the Japanese tsunami of 2011. The difference isn’t attributable to better ­plan­ning, stronger buildings, or quicker evac­­u­ations. It’s simply a function of population. Millions of people live on the coast of Japan, whereas the Washington and Oregon coasts are barely inhabited. There are no nuclear power plants along the coast of either state.

          State and federal officials wrestle with the question of rebuilding Ocean Shores. In the end, the town is abandoned to the sea. The National Oceanic and Atmospheric Admini­stration partners with the Environmental Pro­tection Agency to remove hundreds of fuel-oil tanks and other hazardous material to prevent leaching into the ocean.

          By its one-year anniversary, the event has become known as the Great Cascadia Earthquake. It was the most powerful earth­­quake known to have hit the continental ­United States, and one of the three most powerful earth­quakes since modern record-keeping began. It triggered tsunami surges of up to 51 feet in Ocean Shores, Seaside, Cannon Beach, Newport, and other coastal towns and traveled up to six miles inland. In addition to the deaths, FEMA confirmed 27,567 injured and 135 people missing across 37 counties, as well as more than 42,500 buildings damaged or destroyed. One dam on the Columbia River came close to collapse. Around 3.5 million households in the Pacific Northwest were left without electricity, and one million with­out water. Estimates placed insured losses from the earthquake alone at $5.5 billion to $14.6 billion. The overall cost could exceed $30 billion, making it one of the most expensive natural disasters in American history.

          The earthquake moved North America 57 feet west and shifted the earth on its axis by esti­mates of between 8 and 20 inches.

          The Great Cascadia Earthquake also left a number of people jobless, including Patrick Corco­ran. That didn’t last long, though. Within six months, he is running FEMA’s state­­wide recovery effort. People on the coast recognize him now and then from his ­tsu­nami-preparedness work before the ­disaster. And they thank him.

          “All those years,” he’d tell people, “I kind of felt like the boy who cried wolf. But what people don’t remember is how the story turned out. In the end, there really was a wolf.”

          http://www.outsideonline.com/outdoor-adventure/nature/Totally-Psyched-for-the-Full-Rip-Nine.html?page=all

  16. Avcan FB Comment by Avcan

    Today started with a 2.6 in the calm sea, and another very close to the NNW. The third has been more shallow in the area of peaks, with one brief yesterday in the same area. The rest of the activity is concentrated by the area of summits, the Julán and the mar de las Calmas, until almost the eruptive area. Lineups for all tastes and as earthquakes are arranged in a curious way, forming three arches, maybe one more.:

    the first arc with Center in the eruptive area of la Restinga begins in the mar de las calmas at address N, to go turn Ne entering by the coast, Julán, passes the area of summits and goes to the town boundary where turns to address Jan

    the second arc estáría centered more or less in the Centre of the island and goes from the eruptive area in NNW direction to turn the N to enter along the coast to the summits zone and begin to turn to the NNE in the Gulf to the West of the Tanganasoga

    the third arc is not so clear, but would be focused on the Tanganasoga and empezaria border in direction, to go turn the S pass Ridge through the center of the island, turning SW, going out to the sea in cala Pinar in SW direction and turn direction w. (Henry)
    4 hours ago · Like · 8

  17. Avcan FB Comment https://www.facebook.com/profile.php?id=1133792867

    I guess that a debate on whether or not are is left open to events LP… copy what has been talking about in another post:

    Itahiza Domínguez Sardinia – > I have warned of this. Both the yesterday and today are regional earthquakes and not events LP.

    Mari Angeles Lopez – > Itahiza, if they were regional earthquakes as you say, would be reflected in other stations, and with more clarity than in CHIE

    Itahiza Domínguez Sardinia – > depends on where the earthquake comes. Aki tend to be of the dorsal atlantica with what first reach the Islands omelet. An LP hardly would be on other islands

    Octavio Fernández – > Itahiza, I think that I am not the only that you be very grateful if us dieses a less concise explanation of the apparent LP.
    There clear somehow, any question of bundle, in which not connoisseurs we can set to make the distinction between LP and, as it seems, earthquake regional?
    The signal also appears in other stations, such as EGOM, EHIG or EOSO.
    Thanks in advance.

    Itahiza Domínguez Sardinia – > 1. Precisely the fact to see other islands with so little difference (d) scale tells you that the origin of the signal is not in El Hierro. When the tremor seen in other islands CHIE was saturated and looked only at EOSO.

    2. Such events are common with this form in the spectrogram. If looking for earthquakes located in the Ridge you will see what I say…

    • Itahiza:
      “I’m sure what you see is soo T wave is transmitted through the water. By not seen either the P or S can not be located. An example. Old would be:
      Not be located not mean that none exist. You can not always locate because there are not many stations in the Atlantic … “

  18. https://www.facebook.com/profile.php?id=100002132433634

    lo que aparece en el centro del mapa, una pequeña nube de puntos, es el tanganasoga? hay bastante concentración en esa zona… Por lo que he leido por aquí, ese volcán es peligroso, pero ¿qué peligrosidad puede tener ahora? quiero decir, los volcanes no siempre tienen el mismo comportamiento a lo largo de la historia, ¿no? creo haber oido que en estratovolcanes pueden darse erupciones de varios tipos com efusivas o estrombolianas o con más o menos agua y por lo tanto mas o menos explosivas… ¿qué se puede esperar si sale algo por ahí? que esperemos que no por supuesto, porque está el jorobao en muy mal sitio…

    what appears in the center of the map, a small cloud of points, is the tanganasoga? There are enough concentration in the area… From what I’ve read here, this volcano is dangerous, but what danger can have now? I mean, the volcanoes do not always have the same behavior throughout history, right? I have heard that in stratovolcanoes may occur eruptions of several effusive com types or Strombolian or with more or less water and therefore more or less explosive… what you can expect if you get something out there? that hope which does not of course, because the jorobao is very bad site… (Translated by Bing)

  19. Another Volcano Stirring?

    http://diariocorreo.pe/nota/70170/indonesia-volcan-lokon-registra-dos-erupciones-de-intensidad-media/

    Lokon volcano, located on the Indonesian island of Sulawesi, recorded today two eruptions in a few minutes, although heavy rainfall in the area prevented that clouds of smoke and ash, create reported sources of the disaster management agency of the Asian country.

    The authorities have pointed out that the eruptions were of medium intensity and have set the safety radius 2.5 kilometers from the crater.

    The Lokon alert is located at level 3, a single step of the most dangerous, before the recent increase in activity that has led to recent eruptions, the last of them on 13 February.

    The volcano, 1.580 m tall and located about 20 kilometers from the regional capital, Manado, has experienced a strong activity in the last two decades.

    Indonesia is located in the so-called “ring of fire of the Pacific”, a zone of high seismic and volcanic activity. EFE / / photo: EFE

  20. I have a question – when rifting fissures occur do they occur top down, or from the deep upwards?
    In other words, if an underground fissure starts opening could magma flow underground into the openings without any visible sign on the surface? I am thinking of Iceland here and some of the odd tremor patterns at some SILs

    • How the rift forms really depend on how the stress is applied, and what regions of rock fail first.

      On popular line of thought is that the fissure opens low and magma infills, weakening the rock and assisting in further spreading of the fissure. If it makes it to the surface, you get an eruption.

      The thermal gradient dictates that the rock at the surface will be more brittle than deeper rock. The deep rock is more able to deform and not crack.

      Ultimately, in depends on the dynamics.

    • yes, and you can just barely see activity way out on the left. 2 spots of degassing that are fairly plain when clouds are overhead

    • Avcan FB Comment

      Swarm from midnight yesterday Hawaií seismic, not only occur in the iron and is just under the caldera of Kīlauea, very close where is located the HVO, about 4 km to the NW of the crater Halema ‘uma’ u and about 5 km of depth with two notable earthquakes of 3.0 and 3.2 and a rate of about 6 earthquakes hourly…… continue at this time. Zoom in on the map, is spectacular. When that despresurice, the Kilauea we will offer a new eruptive show… a regret that already is in eruption… (Henry)

  21. Does anyone know when the helicopter for AVCAN is going up next? I would give my left arm to see what’s going on out there…

  22. @Hekla´oholics: Suppose, alledged magma flowing within its many chambers/sills/mesh, is something that has happened before (often or always?) and is “one condition” for “successful” eruption, along with strong enough “transitient”. Thus mix of magmas creating the needed “explosivness” Can this be ? *This crossed my mind as microseisms seem ongoing / present on increase* see http://hraun.vedur.is/ja/hekla/oroi_mjo.html

    • Yes, I do think that is in part what is happening. But we should remember that the magma is basically the same, but it might be more or less evolved in different chambers.

      What has me surprised is the shear amount of magma that has moved with so little evidence of it. In any other volcano there would have been tremendous tremor really. Here it is almost silent as a whisper. But then, Hekla is the silent type. My take on it is that every little passage is allready open, and haven’t closed since the 1947 eruption.

  23. Avcan FB Comment By Avcan

    time has not seen the above by Itahiza Domínguez Sardinia. I explain that there is no doubt: the speed of seismic waves (land: P) for the area of the Canary Islands is established between 6 and 7.3 Km/s.

    The speed of a wave in the water (T) is 1, 45-1, 5 Km/s.

    CHIE-CHIG lag time: approx. 1 min. Distance CHIE-CHIG93 km. speed: 1.55 Km/s

    CHIE-EGOM lag time: approx. 1 min. Distance CHIE-EGOM 87 km. speed: 1.45 Km/s

    By force, it has to be a wave that travels through the water, a T wave, besides there is no amplitude difference. Then no doubt: TELESISMO somewhere in the Atlantic. (Javier)
    about an hour ago · Like · 7


  24. Slyssalda and Snaebyli also showing tremors.
    I know that there should be many many more quakes before an eruption but there is a suggestion in the paper by Soosalu & Einersson that other studies and observattions show that Gasses collect at the top of the magama chambers and these may have the effect of “compressing” the magma..
    I wondered about Hekla somehow being linked with Torfajokull and so the movement Hekla’s “disappearing” magma into the chambers beneath Torfajokull was possible, and this movement is being picked up by Slyssalda and Snaebyli. But having read this paper I think this is highly unlikely.
    https://notendur.hi.is/heidi/Data/Article-richard/SoosaluEinarsson04.pdf
    This is a good paper to read for information about Hekla and Torajokull, particularly in describing the possible depths and volumes of the respective magma chambers…
    There are no clear answers. We all must watch and wait to see what may happen next!

  25. “The team of geology and Marine Geophysics of the IEO of Madrid, aboard the research vessel Ramon Margalef, has made these views in 3D from the bathymetric data obtained in the campaign Bimbache-1011-9 during the 7 and 8 February 2012.” “The presence of the new cone secondary, 75 metres in height located on the flank can be seen in some of the views are of the main cone.” (Translated by Bing)

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