Adriatic Bop – Italian Quakes

Picture from IB Times. End of Time.

Recently there was a rather significant Earthquake in Northern Italy along the Po valley. Rescue and recovery efforts are still underway. With luck there will be no additional injuries due to aftershocks and building/infrastructure failure. Though unfortunate, this quake does afford us the opportunity to look around to see what is going on… geologically.

I would like to thank KarenZ whose plots put me on to this line of inquiry.

There is a lot going on in this region, and the structures there are somewhat complicated (to me) but in essence, the Adriatic or Apulian Plate broke off of the African plate and is wedged between the two. Where it is pushed North , the Alps were formed, to the Southwest, the Apennine Mountains formed and make up the familiar “spine” that runs down the Italian peninsula. The northern section of this range between the Po Valley and the Ligurian Sea is the region of interest. It seems that there is a pretty ancient subduction structure here that has a plate section hanging almost vertically underneath the mountains. (see Fig 1 of Margheriti et al). It is suggested that this is not a classic “subduction zone” but could be some exotic structure made up of continental crust fragments frozen in place in said paper.

Why do I bring that up? Well, the focal mechanisms for the two largest quakes show faulting similar to that of a subduction zone… specifically reverse faulting. The dangling slab in the last paragraph is not it.

USGS Moment focal tensor solutions (beach balls) of a fore-shock, the main-shock, and an after-shock of the large Italian earthquake.

In reverse faulting, the headwall is pushed up over the other side of the fault (relative to the other side) or the other side is being pushed under the headwall. (same motion, just different ways of looking at it) For this quake, it is actually oblique reverse faulting since it is pushing off to one side a bit. (the ball isn’t perfectly lined up).

The question about the Bulgarian quakes came up , but those have a completely different solution. They show normal faulting where one side slides down and away from the other. (or up and away). The only things those two quake sets have in common is.. um.. nothing. They were along the northern boundary region of the Agean Sea plate and the Eurasian plate. There may be some regional stress that caused them both, but as for fault lines, totally unrelated.

So.. what is with the Apulian Plate and how did it get there? Well, that’s the really wild thing. It seems (according to diagrams in reference 4) that the toe and heel of Italy, and part of Greece, originated in the gap in the North African coast down around Tripoli. During this drive north the Alps were formed. Massive folding and crumpling occurred as the land was tortured into position. Anticlines and Synclines formed and eroded, and the leading edge of the collision warped and formed a basin…much like the Persian Gulf between the Arabian and Eurasian plate collision or the Ganges valley on the Indian Plate to Eurasian Plate collision. As some of you know, the top of the Matterhorn is African crust. Did you also know that it is upside down? That’s how extreme the collision is. (pg 14 of Ref 5) In fact, one anticline was an island in a shallow northern Adriatic sea during the Pleistocene, the Ferrara Anticline, buried about 20 km northeast of Modena in the Po river plain. (ref 2 and 3).

Okay, enough rambling.

From reference 3, a modified Figure 1.

In this document I noticed that the study area covered a rectangle directly covering the quake area. Taking a position on the Northeast end of that box, I was able to calculate the distance to each quake and plot them in relation to the cross sectional strata of the study area. As you can see, the fore shock and mainshock occurred in the Mesozoic era limestone that was laid down when this area was part of the sea. Most of the aftershocks are along the interface of that layer and a lower ancient Tethyan crust. Only one quake in the USGS set shows as being in that part of the crust.

The dangling slab is not shown in this plot, and I did yank the mountains off the top. (They were represented in a different scale).

Thank You for your time.

GeoLurking

References:

1) “The subduction structure of the Northern Apennines: results from the RETREAT seismic deployment” Margheriti et al, ANNALS OF GEOPHYSICS, VOL. 49, N. 4/5, August/October 2006

http://earth.geology.yale.edu/~jjpark/Margheriti_etal_Annali_2006.pdf

2) “HYDROGEOLOGICAL FEATURES OF THE PO VALLEY (NORTHERN ITALY)” Bortolami et al

http://iahs.info/redbooks/a120/iahs_120_0304.pdf

3) “A new active tectonic model for the construction of the Northern Apennines mountain front near Bologna (Italy)”, Picotti et al JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, B08412, doi:10.1029/ 2007JB005307, 2008

http://www.ees.lehigh.edu/ftp/retreat/outgoing/preprints_and_reprints/picotti_pazzaglia_2008_Apennines_final.pdf

4) “FROM THE TETHYS OCEAN TO THE MEDITERRANEAN SEAS: A PLATE TECTONIC MODEL OF THE EVOLUTION OF THE WESTERN ALPINE SYSTEM” Biju-Duval et al lNTERATlONAL SYMPOSIUM ON THE STIUCTUIAL HISTORY OF THE MEDITERIANEAN BASINS. SPLIT (YUGOSLAVlA) 15.29 OCTOBER 1976.

http://archimer.ifremer.fr/doc/1977/publication-5197.pdf

5) “Tectonic evolution of the Alpine orogen” Jacques Charvet

http://www.sklable.ac.cn/uploads/file/Jacques%20Charvet.pdf

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98 thoughts on “Adriatic Bop – Italian Quakes

  1. Brilliant! Now I have a pretty good idea why that ancient and long-extinct Italian supervolcano remnant ended up on its side so volcanologists can trace its plumbing from what once was the surface, through the magma chamber and below.

    I tried to locate it by googling, but the web is so full of crap these days that all you get when you search for “Italy/-ian supervolcano/-nic remnant” is 1,000,000 results for Yellowstone. Add the parameter -Yellowstone and you get 1,000,000 results for Lake Toba, Taupo, Campi Flegrei etc. Make certain it only searches the selected parameters and it finds nothing – and I bloody well know I’ve read a couple of articles on it not more than two years ago.

    F-k the moonies and the intellectual pollution of the Internet they cause. 👿

    • When you remember the name of that tipped over supervolcano please tell us. 🙂

      I wonder if the Moonies does not whine a lot about their searches for Nibiru and other tripe leads them here… :mrgreen:

        • ~Henri. Hmm – As google moves increasingly towards dumbing down and social search, I think there is a case for a new search engine which only indexes peer reviewed or referenced articles, blogs and sites – i.e they have to go through manual review or meet some defined ‘authority’ criteria to get approved and indexed. Would take some funding though…. in the meantime, try Google Scholar – its the closest thing there is to such an ideal at the moment, but it only includes peer reviewed publications. Dmoz is too limited…

    • Thank you! I’ve been trying to remember that one myself – there is igneous rock in the Bernese Oberland to the north of Sesia Valley but the Alps are not supposed to be volcanic as far as I know (but *very limited knowledge*TM).

    • Thanks firstly to GeoLurking for a really interesting post. With regard to Henriks link above to National Geographic.com “This allows scientists to see 15 miles (25 kilometers) of the supervolcano’s inner workings”…In volcano terms is 25 km really deep enough to see the inner plumbing of a volcano? In my mind I had an idea that to get to the bottom of a volcano you would have to go to the centre of the earth and would that not be thousands of km underground?

      • You’re of course right, but 25 km is still deep enough to show the uppermost magma chamber of most “supervolcanoes” in their entirety even if the magma plumes that feeds them go down several hundred, if not thousands of kilometers. As an example, the main Yellowstone magma chamber is thought to extend from about six to sixteen kilometers while the deep roots, the magma plume, goes down at least 660 km.

    • Would the sesia valley supervolcano in Italy be caused by the Tibesti / Chad hotspot which ones hypothetical track is depicted in this article? Sorry it´t in german, but look at Fig 18.
      http://www.dgg-online.de/mitteilungen/2003_4/Digital%202.pdf
      I came across that publication looking for volcanic activity in my area and was excited that a hotspot may have acted right under my feet in now flat northern germany 300 ma ago causing a gravitational anomaly. Unfortunately, so far I found no other supporting references.

      • Tibesti is a good candidate.

        The coast line at Tripoli is about 1258 km from the Tibesti hotspot’s position. assuming that the African Plate has had constant movement, that would place the area around Tripoli over Tibesti about 140 million years ago.

        (note for all, Hotspots seem to be “fixed” with relation to the Earth’s core, with the plates jostling around on the surface

  2. GeoLurking, Thank you for the article and the papers.

    There is alot of reverse folding in the Alps, which I had understood to be caused by the collision of the Eurasian Plate and the African Plate. I found the Apulian Plate because the pattern of EQs for Italy was not what I had expected from my simplistic understanding of the movement of the African Plate. A Google search on the Adriatic Sea came up with the answer.

    I also found that the subduction of the African Plate under the Apulian Plate is supposed to the origin of the volcanism in Southern Italy – which is where many of the deeper quakes on my recent plots occurred.

    The African Plate is relatively slow moving so does not appear to produce many large EQs.
    A better source for European EQs, if you want EQs <4.5, is EMSC http://www.emsc-csem.org/Earthquake/?view=1 Select "Search earthquakes" under "Earthquake Information".

  3. @Lurking:
    WE are the ones who should thank YOU for YOUR excellent post!
    Great food for thought here.
    No wonder that the whole Italy is so seismically active, and I fear there will be more surprising, perhaps, devastating events happening anywhere in this region. I only hope I’m wrong!
    And Henry, this ancient supervolcano’s plumbing system under the Alps is totally new to me! Cool stuff!
    I suggest all readers to take another look at Boris’ articles from EB (also in the VC “treasure”, I suppose?) about Etna/Sicily geodynamics, just to grasp a bit more information on the intricate tectonics along the Italian “boot”.
    @Lurk:
    Still waiting for some in depth analysis of recent megaquakes off the coast of Northern Sumatra. Maybe there is nothing special about them, since nothing further has been said (yet). But I’m convinced that a new “earthquake front” has opened in that area, still as a consequence of the great 2004 event. But maybe I’m wrong…
    Is it asking too much? 🙂
    Thanks again!

    • Here is an extract from my plots (in the process of being updated). There does appear to be new activity (activity between 2010 and 2012) in the area 1.847N, 86E to 93.4E.

      • Also reported around the time of the Sumatra EQ: http://www.bbc.co.uk/news/world-asia-17675399

        Extracted from this report:

        Roger Musson, a seismologist from the British Geological Survey, said the quakes were unlike those seen off Indonesia in recent years, where ground had been pushed under the continental plate, “flipping up” the seabed.

        “It seems to be a large earthquake within the Indian Plate and the plate has broken in a sort of lateral way,” he said.

        “It’s a sort of tearing earthquake, and this is much less likely to cause a tsunami because it’s not displacing large volumes of water.”

  4. Thanks. I was surprised to find out that the top of the Matterhorn, the African Crust segment, is upside down.

    The land was folded back upon itself as can be seen in the diagram in the link for ref 5.

    For Renato: The offshore set for Sumatra is along a convergent oceanic boundary for the Australian plate and the Indian Plate. The Indian Plate is pushing north at about 48 mm/yr, slamming into Eurasia, The Australian plate is doing almost twice that speed (70 mm.yr) and is hitting along the Sunda Trench.

    The western extend of the Australian plate is behind the Indian plate, and is hitting it from behind, making the convergent oceanic boundary where the offshore quakes are at. This collision is probably at about 22 mm/yr. (70 mm/yr – 48 mm/yr)

    • I thought this boundary had been considered inactive, but I see that I was wrong to suppose so.

    • I don’t see how a truck pushing on your rear bumper can be considered “inactive”

      If this region became truly inactive, then that would mean the Indian plate and Australian plates were effectively sutured together.

      • I thought I have read they were so “sutured”.
        Probably I mixed up some information here.
        Thanks again!

        • Well, for the most part they are… “sutured”… at least enough to where they tend to operate as one unit in that area.

          But if you note the speed differences from one end to the other end, treating them both as one unit, there is some serious rotation going on (geologically) or there is stress building between the two.

          I think these “reactivation” quakes reflect that stress.

    • After climbing rather reluctantly up Matterhorn I seem to remember through the but too well remembered fog of fear that the stratigraphy was rather odd. Back then I did not know a whole of a lot about rocks and layering, but if I remembered that it looked odd while I was pooping my pants out of fear, then it is probably something.

      Oh, and for the record, Matterhorn was the first and last mountain I will ever climb… Things that stupid young men do after a dare.

      • I stick to mountains that it is possible to walk up slowly – preferrably with a restaurant at the top with a decent cup of coffee (the red wine has to wait until you have made it back down again – unless there is no restaurtant so you have to take your own beverages for the entire day).

        • Try walking up Victoria Peak in Hong Kong.

          Started out pretty lit up… got to the top stone cold sober. Then we realized it was the next peak over.

      • I thought it was worth the view, I did a bit of climbing in my younger days, going down was a bit more of a challlenge. I always thought there there where a few volcanoes in the Alps, you only have to look at their structure and what about the Bodensee, looks like a caldera to me

        • Bodensee, itself, is an old glacier basin. I agree some of the geological features in the Alps appear to have more than glaciation and folding as their cause but *very limited knowledge* TM.

      • I had a climb up Mt. Shasta as a yoot. 14,162 feet at that time. Sulfuric fumaroles near the summit, awesome glissade back down.

  5. @Spica and the Dragons….

    Could you take the Beach Ball image out and replace it with this one?

    This is the one that didn’t make it across in the email (though it is buried in the mht file).

    Thanks!

    • Problem was that I could not open the mht-file… Gmail garbles things that it does not recognize.
      Fixing now.

      • That’s the part that is un-settling. The whole she-bang was rolled up in a rar file. Google has no business opening up and archive and looking inside of it.

        • But it opens it, and reformat things into their own weird formats. And not only that, even if google does not understand the format, it still redo it into a google format, that is totally unreadable for anyone… Sigh…

  6. I just came across this report http://www.jpl.nasa.gov/releases/2002/release_2002_217.cfm which discusses that the shape of the earth has been changing, although I am seriously struggling with the proposed explanation for this phenomenom. Glacial melt would result in rebound surely, exaggerating the elongation, not the other way around? I wonder if any of you had any thoughts about the phenomenon and if it would have any practical effect on either volcanism or earthquakes if the change is maintained.

    Re Diana’s post – thank you. Its a shame it is so topical at the moment.
    http://www.theolympian.com/2012/05/22/2115432/peru-agency-says-cause-of-dolphin.html#storylink=cpy

    • Sorry – I should have added that the geoid shape change is an old piece of data / news but was still news to me, and interesting!

      • And also the thing I am struggling with is how the earths gravity field would be altered by glacial melt – GeoLurking… I think you may have the answer to this?

      • All matter has gravity (generates a gravitational attractive field).

        For the sake of argument, assume that we have a one kilogram reference object (for the purposes of calculation.. and to avoid a bunch of vector stuff)

        Now take a cubic meter volume of granite, with a mass of 2700 kg and place it 1000 meters from our reference object.

        The attractive force between the two is about 1.80194 x 10^-13 N (m/kg)^2

        If we substitute one cubic meter of pure water instead of the granite, that force drops to 6.67384 x 10^-14 N (m/kg)^2

        This is a reduction in gravitational attraction (between the one meter cube and our reference one kilogram mass) of about 2.7.

        Earth’s gravity comes from the totality of it’s mass. Different parts of the earth have difference densities, and therefore different contributions to the sum of all of it. When mass moves around, the local gravitational field changes to reflect the new distribution of the stuff that contributes to it.

        Whack an icecap, and the stress fieid of it bearing down goes away, and the lithosphere rebounds. In the short term, the local gravity may drop to reflect the loss of mass. Denser material eventually takes up space in the region where the ice used to be and the over all gravity field will go up… compared to the missing ice. This is all in reference to a fixed point over where the Ice was at.

        Since the rebound is only going to attempt to restore buoyancy, the terrain will not achieve the same altitude as the top of the now missing icecap. (granite is 2700 kg/m³, ice is about 934 kg/m³)

        What is measured in the gravity field surveys is what the local sum attraction is… and that is all dependent on what is around that area.

        A simple / added by Spica.

          • OK- that understood, i.e how the gravitational field is affected at the ice caps, but by what mechanism would the loss of gravity at the ice caps result in an equitorial increase in Earths diameter (in the article referred to as an expanding waistline)… Thanks in advance! While I can see the effect, I am still struggling to envisage how such a relatively small localised physical effect could have such a large scale global consequence…. unless we are saying that the earth is particularly sensitive and responsive to minor changes and fluctuations in gravity at different points on its surface?

          • That’s really weird. What causes the Earth to bulge out of spherical is rotational flattening. The authors must think that because a) the net effect of ice-cap melting would be a loss of polar altitude, and b) freed water would move to the equator, the sum would be a polar decrease and equatorial increase.

          • And with the movement of mass from near the axial center of rotation to the periphery, you would have an overall slowing of the rotational velocity.

            This conserves angular momentum, and the entire earth would slow (ever so slightly) in order to preserve that balance.

            Slower velocity, less force making the bulge.

          • One should remember that earths rotation time diminishes steadily over time.
            Also, one should remember that there is no thing like a stable orbit as soon as you have more than 2 orbital objects.
            So, here is a bit of a fun facts.
            1. The moon is falling down upon earth (The sun will die before it hits… But imagine what the Moonies will say in half a billion years when the moon is twice the size of today?)
            2. The Earth is falling towards the sun (The sun will go read giant before this happens)
            3. Mercurius is falling away from the sun (might hit earth in a billion years)
            In short, what we know as the solar system will be basically horked in one billion years. Personaly I do not loose that much sleep over it, when that happens I plan to be a VR-simulation running on a black hole as a universal computer.
            The real question is probably if I am truly Turing-compliant.

          • Yes, the moon is falling down on Earth, but it gets further away as it does… about 38 millimetres per year.

            (WackiWikiPedia used as a quick reference… but I can dig for it if it’s important)

    • I ‘think’ it’s not talking about polar ice melting and it’s talking about other glaciers (on tops of mountains – and possibly (depending on time scale they are talking about) the results of the ice age glaciations) melting and the rebound occurring more in regions that are not at the poles is starting to make the earth more oblate (fatter around the middle).

      sorry for my nested brackets

  7. Thanks Lurking – great article!

    As I am currently on holiday in Cyprus the 1222 earthquake is still evidenced in ruins around Paphos. And as all of you probably know – Mt Olympus is where the mantle sticks right out on the surface.

    I am watching Santorini – I fancied Sicily or Santorini for a holiday but got out-voted – and Santorini seismic monitoring had a strong peak for the 5.5 in Cyprus, which has unnerved the locals a bit! For the Italian quake there was a long and steady pulse on the seismic HL monitor, and there is a build up of activity ongoing, not to mention all the quakes all around the Adriatic – very active at the moment.

    There were pre and after-shock quakes for Italy and Bulgaria. Just watching….
    Dragged from the vaults by Spica

  8. Thanks Lurking – great article!

    And as all of you probably know – Mt Olympus is where the mantle sticks right out on the surface.

    Santorini seismic monitoring had a strong peak for the 5.5 in Cyprus, which has unnerved the locals a bit! For the Italian quake there was a long and steady pulse on the seismic HL monitor, and there is a build up of activity ongoing, not to mention all the quakes all around the Adriatic – very active at the moment. Seems to be centred on the area around Santorini.

    There were pre and after-shock quakes for Italy and Bulgaria. Just watching….

    Not sure if this post got lost just now or if it will appear twice.
    Best wishes all
    Rescued by Spica

  9. Curious for people who may know better, Popocatapetl has been puffing away for an entire month now. Is this within the realm of “normal” for a volcano like this? I know it’s known to let some steam loose from time to time as many volcanoes do, but I don’t recall it ever having done so for such an extended duration at such a constant rate. It kind of seems most volcanoes that “burp” do so, but only for 1-2 weeks at a time tops.

    • Not an expert here, but if you take, for instance, the recent Puyehue-Cordon Caulle eruption in Chile, you have an unceasing ash plume from June 2011 up to April 2012. And still within “normality”.

    • Perfectly normal. As Renato says, there’s the recent Puyehue-Cordon Caulle eruption although it’s brief compared with a couple of other still on-going eruptions: Soufrière Hills Montserrat has going at it since 1995 and is not done yet. Sakurajima has been erupting since 1953, no less 59 years.

  10. Fer da dragons.

    If you could add a close bold tag on my 22:06 so that it reads:

    “…For the sake of argument, assume that we have a one kilogram reference object…”

    I would appreciate it.

  11. Lurk, that’s a heck of a piece! Matterhorn being made of African rock, flipped rock… The kids’ reaction: “cool, then there must be upturned volcanoes too!”.

    • Well, yeah. Earlier in this thread was mentioned a Large Caldera structure (supervolcano) that has been laid on it’s side and is eroded down to where you can walk around and explore it in cross section down to a depth of 25 km.

      It’s the Sesia Valley fossil supervolcano and it erupted about 290 million years ago.

      See: Henri le Revenant – May 24, 2012 at 12:13 at the top of the post.

      • Kids meant volcano that erupts into the earth…
        Thanks for pointing to Henri’s comment, must investigate. My reading is a bit into scanner mode at the moment, too much happening right now in the rest of my life…

  12. Deep quake.

    Friday
    25.05.2012 01:10:45 65.134 -16.450 14.8 km 2.1 90.01 6.0 km NNW of Herðubreiðartögl

  13. Regarding the ongoing quakeswarm in the Norwegian sea.
    There is actually a faint possibility that this was the onset of an eruption. Technically it was a double couple, and the orientation is fairly consistant with a rifting. Historical beach balls also point to an actively rifting fissure.
    http://neic.usgs.gov/neis/bulletin/neic_b0009ym3_m.html
    Also the high number of large afterquakes have a cosy hammock-look to them, with an open large quake, smattering of smaller quakes, and then revigoration with several larger quakes.
    I might be wrong, but it looks like the later quakes are comparatively “wetter” with longer duration times, something that can point towards magmatic components.

    Beach Balls:
    http://earthquake.usgs.gov/earthquakes/eqarchives/fm/neic_b0009ym3_cmt.php
    http://earthquake.usgs.gov/earthquakes/eqarchives/fm/neic_b0009ym3_fmt.php

  14. Quote Carl le Strange: “But imagine what the Moonies will say in half a billion years when the moon is twice the size of today?”

    Blimey! It’s 3474.2 km in diameter now so in 500,000,000,000 years (English) or 500,000,000 years (US perversion), the moon will have grown to 6948.4 km, or roughly the size of Mars. Amasing!

    😉

    • Or left Earths orbit by then and be gone. If I recall correctly there is one man constantly measuring its move AWAY from us (Earth), of about 1-2 cm per year ????

    • Though.. to be technically accurate, All planets gain mass over time. Earth accumulates about 92 to 194 tonnes per day. At 1/6 of the Earth’s gravity, a reasonable estimate would be 15 to 32 tonnes per day for the Moon.

      All from dust, meteors, and debris from passing spacecraft.

      So yeah, it is “amassing.”

      😀

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