Sheepy Dalek, Kick ‘em Jenny and “stuff”

Here are the results and answers to the last Friday Riddle.
An extra page was created for the answers of Name That Volcano(es) which can be found by clicking the link or you can search for it in the menu under Gems.
A hint from me, check the old Riddles frequently, you will notice certain patterns the riddlemasters use. This works especially with Alans and Suzies riddles. Name That Lava is a different story. Here you have a better chance if you ever were in this area and the landscape looks familiar. A tip here, even though i do not have the slightest clue when the next one of those will go in again. Looking for hints of vegetation can give you a decent hint in which region of the world the answer could lie.

RIDDLE – Name those Volcanoes # 9 went in on Ruminarian II – Tolbachik… Author GeoLurking December 7^th.

The first was briefly the subject of a ‘blague Francaise’
The second used to have vents (now pits) that share their name with a footballing legend
The third is the only volcano within the arc of the SS islands chain to have erupted rhyolite pumice
The fourth is located approx. 3 kms due west of a small group of ’sibling’ rocks
The fifth shares its name with a species of lacertid

One point for each volcano and one point for spotting the link!

No 1 Surtsey
http://en.wikipedia.org/wiki/Surtsey
No 2 Lo’ihi Seamount
http://en.wikipedia.org/wiki/L%C5%8D%CA%BBihi_Seamount
No 3 Protector Shoal
http://en.wikipedia.org/wiki/Protector_Shoal
No 4 Kick ‘em Jenny
http://www.uwiseismic.com/general.aspx?id=27
No 5 El Hierro
http://www.arkive.org/hierro-giant-lizard/gallotia-simonyi/
http://www.konicaminolta.com/kids/endangered_animals/library/field/eh-giant-lizard.html

The link was submarine volcanoes

Well done and points to -
KarenZ 1 point
Sherine France 3 points!!
Chryphia 1 point
Alison 2 ? 1  points

# 1 Surtsey – Alison
# 2 Lo’ihi Seamount – Sherine
# 3 Protector Shoal – KarenZ
# 4 Kick ‘em Jenny – Sherine France

Chyphria for the link between the volcaoes. All of them are submarine volcanoes!

Ranking for  NtV: Ranking December 8

4 Sherine France 3 or 2 Alison 3 Kelda 3 Chryphia

2 Spica 2 Sissel 2 KarenZ 1 UKviggen,

1 Stoneyard 1 DebbieZ 1 Inge B 1 Grimmster ,

One of the correct answers to the seamounts we were looking for was Kick ‘em Jenny.  A submarine volcano which interests me ever since i first heard of it, when Erik Klemetti was looking for odd volcano names on his blog Eruptions more than 2 years ago.
So here comes a sum up on Kick ‘em Jenny with links and whatever i could find on it on the internet.
Obviously the name refers to the rather harsh weather conditions which often occur in the sea above this seamount. And dont worry Kick ‘em Jenny is not a lonely volcano, it does have more vents around and one of them is called Kick ‘em Jack. It is a volcano which is caused by the Lesser Antilles Subduction Zone and watched because an eruption may cause tsunamis as it has happened before in 1939.  On some old maps an island is shown in the region where the volcano is now situated. I could not find out if an old version of this volcano really was an island before, though it could not be totally impossible as long as the 2003 survey found an  arc shaped collapse structure extending towards the west.

Sonor image of Kick -ém Jenny found on Wikimedia Commons.

Kick -ém Jenny lies about 8km north of Grenada within the Lesser Antilles. It was discovered in 1939 when a spectacular eruption took place and Jenny broke the surface in a surtseyan style eruption. It is said to have thrown steam and debris up to a height of 275 m (902 ft). How this could be measured so exactly is beyond me. The eruption took place on 2 days, 23 and 24 of July in 1939. It was not the first eruption for sure, just the first which was observed. Ever since, the submarine volcano has erupted at least 12 times but this was only speculated due to seismic activity and it could not be watched from ships on the water.  Kick -ém Jenny never stayed above seafloor or created an Island. At the moment its peak lies around 180 meters below the seasurface, where it has been in 1966 also. Mariners had been believing that the volcano had grown and was as close as almost 40 meters to sealevel but a research in 2003 could not confirm those expectations. Kick -ém Jenny is a very active volcano and ships should stay away from it in an exlusion zone of 1,5 km around the seamount.

Map from Wikipedia Kick -ém Jenny

The University of the west Indies has a page on ithe seamount and from there you can also find the detailed daily logs of an expedition of NOAA´s ship Ronald H. Brown which took place in March 2003 funded by NOAA. In those logs you can also check pictures of the ROV, sea fauna and even of samples which were taken during the survey and sampling 2003. On the main page there are also 2 sea beam images which will give you a better idea of the shape of Kick -ém Jenny, Kick -èm Jack and the surrounding vents.

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Full image can be found on http://oceanexplorer.noaa.gov/explorations/03kickem/welcome.html

When the volcano first broke the surface in 1939 several tsunamis have been created. The University of the West Indies created a chart list with a short description of the events since. The last eruptive event seems to have taken place in 2001. Geology Report of Kick´em Jenny
As long as this volcano is highly active and a rumbling can be heard sometimes, this might not be the last time you can find an post on it here. Maybe it surprises us with some action some time in the future.
This is a sum up done by me, a complete layman who just has a black belt in Google Fu and no expertise in vulcanology.

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References:
Wikipedia: http://en.wikipedia.org/wiki/Kick-’em-Jenny
University of the West Indies: http://www.uwiseismic.com/general.aspx?id=27
Oregon State University: http://volcano.oregonstate.edu/vwdocs/volc_images/north_america/kick.html
John Seach: http://www.volcanolive.com/jenny.html
Global Volcanism Program: http://www.volcano.si.edu/world/volcano.cfm?vnum=1600-16=

It is still the weekend and also a Sheepy Dalek post so let me ruminate about images on the blog a little.
This blog has a library of 3GB where we can store images to be shown on the pages itself. We are currently using 24% of the storage. As long as we are over a year old this may look as if we dont need much space, even though we have 188 posts here already, each of them adorned with pictures. We also harbour 37 pages, some of them even display my library of microscopic images. ( For people who have not already checked that… mostly SEM photos of different volcanic ash can be found in Gems. )
Still, if we are careless this storage is used up soon. GeoLurking discovered recently, if you upload an image again, after one ( in this case me) accidently deleted it, it goes in with the same title with the edition of -1. So even though it is no longer addressable it still counts. This also means, that when space becomes tight, the solution of deleting older images will not help.
So i am asking the dragon not to add audio files and keep a close eye on how much storage is still available. If you check the shopping cart one can buy 10GB of storage for 20$. That is a sum i can and will pay in case it is necesarry, if it is a one time payment and not a yearly sum.
So my thoughts on this. Lets still bring over images by our users, screenshots or something similar when they will expire because they are located on tinypics or if noone would see them because they were delivered in an email. If those images are really huge in size, could they please be worked on before we upload. Maybe add the images into the gallery we have ( did you know? ) within Gems so we can find them again. People who send images or upload them to Tinypic, could you please give the address of the cams or other sources where you took them from.

Iceland experiences a strong gale ( again!) but IngeB noticed a strange patter of earthquakes this morning.

from http://en.vedur.is/earthquakes-and-volcanism/earthquakes/

I took a screenshot and here is IngeB´s comment again:
Has somebody had a look at Iceland quakes lately? If not all of them ghosts (rather bad quality with a lot of them), the actual picture shows a very clear pattern of the TFZ and its two main fracture zones, the Húsavík-Flatey-Fault in the southwest and the Grímsey-(Öxarfjördur-)Fault in the north: http://www.vedur.is/skjalftar-og-eldgos/jardskjalftar Compare eg. to p. 2 here: http://www.sciencedirect.com/science/article/pii/S0025322701001724

Spica

Ruminarian II – Tolbachik

Some of you may have noticed that I haven’t been doing a large number of plots. In part, this is because digging into a large set of data takes a bit of motivation and patience… and a bit-o-time. KarenZ, dfm, and chryphia have picked up the mantle on animated plots, and have each brought their skills using their programs of choice and produced some truly outstanding animated graphics. This has allowed me to focus on learning and reading… sometimes getting it wrong, sometimes getting it right… or at least pretty close to right.

So… let’s ruminate.

Tolbachik is a fissure vent eruption. It wasn’t until this evening that I realized that my initial ideas about what happened were somewhat wrong. Rather than a sill forming (horizontal magma emplacement) which then fed to an upper sill via a dike (vertical magma emplacement), what happened appears to have been the pressure in already emplaced magma fracturing the rock and continuing along the path that it had been working on for several years.

Back in 1975, this system erupted in “The Great Tolbachik Fissure Eruption,” and according to the Smithsonian’s GVP site, placed 1.2 km³ of magma on the surface. For reference, that’s about 8% of what Lakagigar (Laki) did in 1783-85… and at about 11% of the rate. 2.26 x 10^06 m³/day verses Laki’s 2.02x 10^7 m³/day. Either way, it is still phenomenal. Mt St Helen’s did about 1 km³ in it’s flank collapse and lateral blast, but that was a different sort of critter. Tolbachik (and Laki) both do “Flood Basalts” though Tolbachik is a bit anemic in that regard.

However, it is cool to look at and ponder. Here is a combination EO-1 ALI image overlaid in Google Earth, with features aligned so that everything is in proper context draped over the surface.

“Dmitry Melnikov” over at Dr Erik Klemetti’s Eruptions forum spotted the EOS image.

As noted earlier, I had the sequence a bit off in how I was looking at it. (I’m not an expert so I’m allowed to mess up, right?) Poking around at the various links that show up in the threads, one gave us a bit of fine grained data… well, a lot more than we had. Doing a bit of data juggling, I located the data for the plot used in “Northern group of Volcanoes” It plots out like this;

Here you can clearly see the upper and lower sill/chamber and what probably is the connecting dike. It wasn’t until dfm did a close in animated plot that I noticed that the upper region seemed to initiate the events, and then the upper and lower regions pretty much quaked in unison.

Another thing that got my attention as I was poking around at it… was that the brunt of the quakes were no where near where the eruption was at. Maybe a few connectors from the main quake region, but that was about it. This probably is a manifestation of the feed system. (remember, “Bob” didn’t really have a lot of activity from the believed “chamber” to the Jacuzzi… which seemed to be seismically quiet until after the fact)

Juggling programs… (Excel to DivaGis to Google Earth) gives us this:

Notice anything interesting? Yup. Those two pancakes are directly under the main volcanoes. Roughly a line from Gora Bolshaya Udina to Mount Ostry Tolbachik. Had the dynamics been different, this could have been a main edifice eruption of Tolbachik. Even the seeming “connector dike” is directly under the SouthEastern summit. That pretty much means its actually connected with the vent. The magma just found an easier way out. (again, a lot like “Bob” where the main swarm of activity was pretty much under Tanganasoga but the eruption was over next to La Restinga)

Poking around the net… you find that Pay to Play paper sites can really piss you off. One of the most notorious is Springer… but Springer does have something quite neat. A few “freebie” papers that you and I (un-funded armatures) can get our hands on. One of them is: “Determining magma flow in sills, dykes and laccoliths and their implications for sill emplacement mechanisms” Thomson (2006). Here is the search link for it since direct links don’t work with that site:

http://link.springer.com/search?query=Determining+magma+flow+in+sills

In this paper, the author notes that sills tend to be concave upwards. That means that the propagating ends tend to point more and more towards the surface. A combination of forces can drive this, Forced Deformation, or Faulting. Page 197 of the parent publication (or just go to page 15 of the PDF) and you get a really nice visual example of what he is getting at. It’s entirely possible that something like this is what drove that finger of magma moving southward to turn up and broach the surface. (the tendency of this area to rift probably had a lot to do with it also)

Another thing to consider (speaking of tendencies) is that this entire region is made up of teranes that have been slammed into the Okhotsk plate (sort of a subsidiary of the North American Plate in some renderings) You all remember terranes right? Assemblages of crust material that have a common geologic origin and tend to move as a group. In this case, slivers of island chains squashed into the plate, slivers of oceanic spreading center remnants (the central valley region), an ancient volcanic arc (western side of Kamchatka), and … get this, parts of the Hawaiian hotspot’s activity. (up around Shiveluch where the Emperor Seamounts are periodically gobbled up by the current subduction zone)

Yeah… a lot of stuff going on in Kamchatka.

Here is an animated GIF I did the other night…. it was noted that this sped up sequence looked a bit like a frying pan fire. Appropriate.

http://volcanocafe.files.wordpress.com/2012/12/tolbachik.gif

Here is a re-tasked webcam where you can grab a peek at the activity from time to time.

http://www.qicknews.de/Webcams/Tolbachik.php

Enjoy!

GEOLURKING

RIDDLE  - Name those Volcanoes

The sovereignty of first was briefly the subject of a ‘blague Francaise’
The second used to have vents (now pits) that share their name with a footballing legend – the name of this volcano means ‘long’ in the local language
The third is the only volcano within the arc of the SS islands chain to have erupted rhyolite pumice – Solved Protector Shoal
The fourth is located approx. 3 kms due west of a small group of  ’sibling’ rocks – Solved Kick ‘em Jenny 
The fifth shares its name with a species of lacertid – this giant wall lizard can only be found on the Island that bears the same name as the volcano

The link is that they are all submarine volcanoes!

One point for each volcano and one point for spotting the link!

Monte Somma & Vesuvius

Painters rendition of the 79 AD Pompeian eruption of Vesuvius.

The World’s most ill-begotten real estate, Part II

Monte Somma is an old volcano, activity started 400 000 years ago. Over the next 375 000 years a massive strato-volcano was built up at around the same location as todays Vesuvius. The main geological component is guarinite, an epitaxy of hiortdahlite, wöhlerite and låvenite. There is no known record of any caldera forming events during this long period. At the end of the period Monte Somma had an edifice containing four times the rock volume of today’s Vesuvius (calculated conservatively).

The volcanicity in the area is driven by the back-arc subduction zone caused as the African plate slams into the Eurasian plate, and then being pushed under. On the European side melt from the friction of the plates is being released through the Campanian volcanic arc. Other close by members of the volcanic arc is Campi Flegrei and Mount Epomeo (Island of Ischia).

25 000 years ago Monte Somma suffered the Codolan eruption, an ultra-plinian eruption that eradicated almost the entire volcano in a cataclysmic failure of the magmatic chamber. The Codolan ash lies on top of the Campanian Ignimbrite caused by Campi Flegrei 34 000 years ago, making the Codolan eruption the youngest of the cataclysmic events caused by the Campanian arc. The highest remaining point after the eruption is today known as Punta del Nasone (Tip of the Nose), an 1 132 meter high edifice on the caldera rim. The eruption probably had a significant effect on the population size in southern Europe.

Google Earth Image of Vesuvius. On the upper left you can clearly see the caldera wall of Monte Somma with the Tip of the Nose (1132m).

Vesuvius is born

From the ashes of Monte Somma a new volcano started to grow almost immediately. During the first 8 000 years the new volcano had a fairly unevolved magmatic chamber system. As such it could not cause large eruptions, instead it slowly, but steadily built up.

That changed about 17 000 years ago when a cycle started consisting of frequent small to medium eruptions interspersed by Plinian eruption ranging between VEI-5 and VEI-6. To date there has been 8 of these larger events in the current cycle. Calling them large might seem ridiculous compared to the Codolan ultra-plinian event, but one should compare within the cycle. These eruptions are believed to range between 5 and 15 cubic kilometers of ash counted in Dense Rock Equivalent (DRE). Compared to the 0.25 cubic kilometers (DRE) of Eyjafjallajökull these eruptions are rather large.

These larger eruptions take place roughly every 2 000 to 3 000 years. This time interval makes sense if one takes into account that the magmas needs time to fractionalize enough to evolve to the highly explosive magmas involved in these eruptions.

The latest plinian eruption was of course the 79 AD eruptions that eradicated the cities of Herculaneum and Pompeii. I will cover this eruption in a separate article in the series about Neapolitanean volcanicity. This eruption is the reason we call these eruptions plinian. The reason for that being the historian Pliny the Younger (Plinius), writing down the quintessential record of the eruption.

The plinian eruption before that was the Avellino eruption (Pomici d´Avellino) that took place 3 800 years ago. Archaeologists have noticed that this eruption had a large effect on the regional Bronze Age population.

After the 79 AD eruption Vesuvius has had numerous small to medium sized eruptions ranging from VEI-1 up to VEI-5. Some of these have been notoriously ashy. The 472 and 1631 eruptions yielded ash that travelled as far as Constantinople.

Vesuvius today is rapidly getting known as the Garbage Dump of Italy. This is due to a large amount of both legal and illegal dumping of garbage and industrial waste in old flanking vents and cones. This has raised the toxicity around the volcano to a level where one should not eat anything growing on or around the volcano. Even the fabled wines of Vesuvius are now deemed not fit for human consumption. It is sad that Man’s folly is destroying one of the world’s most beautiful vistas.

Technically Vesuvius is a somma-volcano, a type of volcanoes named after its parent volcano. The term refers to a fully developed strato-volcano that has formed inside a caldera of an older destroyed strato-volcano.

Photograph by the US Air Force. Eruption of Vesuvius 1944 taken from a bomber plane.

Risks of Vesuvius

Vesuvius can theoretically have 3 types of eruptions if we look historically. These are in order of threat-level the regular eruptions, the plinian eruptions, and a possible recurring ultra-plinian Somman event. Let us look at them one at a time.

Before we go on I would like to say that the projected death tolls for the respective eruption sizes are from figures that have been calculated by INGV, The Italian Government, The regional government of Naples, independent catastrophe mitigation experts, EU and the UN Decade Volcano Program.

The lower end figure is the best possible figures. Basically it would require functioning scientific volcano predictions, and a high-powered highly ordered Government ruthlessly enforcing evacuations and other protective measures. Basically we are talking about northern European style Government with heavy military aid here. The high figure is based on INGV being disregarded for political reasons, week or no mitigative measures taken, lack of functioning roads being accounted for, and the general nonchalant attitude in the region. I would here say that INGV will do their work; they are highly capable and very diligent in performing their duties. I just hope that they will be allowed to do it by the highly corrupt Neapolitan local politicians.

The risk is of course heightened by the high population numbers, and that people live close to, or even on the flanks of Vesuvius.

Central crater of Vesuvius.

Normal Vesuvian eruption

Vesuvius is a highly prolific volcano, and it is known to have had several instances of magmatic intrusion since the 1944 eruption. The last major intrusive episode was taking place between 1996 and 1999. So far this is the largest of the intrusive events post 1944.

It is highly likely that Vesuvius will have an eruption during this century. When it happens it will almost certainly be in the range of VEI-2 to VEI-4. One should though note that there have been two out-layer small VEI-5 eruptions since the 79 AD eruption and also that there has been a few VEI-1 eruptions. Median eruption (most likely) would be a VEI-3 size. Ash, volcanic bombs and pyroclastic flows would be the largest risk for the population.

Death rate would be between 0 and 100 000 depending on size of the eruption, and the amount of protective measures taken.

Vesuvius in the background photographed from Herculaneum.

Plinian Vesuvian eruption

Vesuvius is from a short geological time-frame ranging in on a plinian eruption. Nothing points towards that the eruptive cycle that started 17 000 years ago has changed to the better. Judging by previous behavior the next plinian eruption will occur during the coming millennium.

The risk of a plinian eruption is driven by the rate of fractionalization of the magmas. Normally this type of explosive eruptive behavior requires the volcano to not erupt for a few centuries before the plinian eruption, thusly giving the magma time to evolve as intrusions bring in new material that mixes with older colder magmas to revigorate the explosivity until the volcano quite literally explodes. This seems to not be the case with Vesuvius. One suggestion might be that there are different magma chambers that are responsible for the larger eruptions and small shallow chamber responsible for the smaller eruptions. Be that as it may, do not expect a long period of repose between a normal eruption and a plinian. Risks for a plinian eruption would be large amounts of ash, large pyroclastic floods, and lava bombs ejected up towards 40 kilometers. There is also risk of tsunamis causing additional deaths in the low laying parts of the Bay of Naples. Larger pyroclastic flows can rush over the water’s surface and hit areas that are not close.

Death rate between 10 000 and 1 000 000 depending on prevailing wind and the amount of people evacuated.

Photograph from Whiteynet. Vesuvius encircled by Monte Somma caldera.

Ultra-plinian eruption

This option is highly unlikely in the foreseeable future. Why? Compared to the size of the Monte Somma edifice we know what the maximum size the volcano can grow to before it suffers a catastrophic fail. Even if we count in the secondary caldera formation normally are smaller than the first one due to damages to the crust we still known that it will take quite some time to build the volcano up sufficiently both above ground and below ground.

If we calculate the growth rate of Vesuvius and compare it with the size of Monte Somma before the caldera event we see that it will take a minimum of another 75 000 to 100 000 years to grow to comparable size. Statistically we know that secondary caldera formations are 50 to 75 percent of the original event size. So, we are most likely looking at something in between 25 000 to 75 000 years of continuous growth before we need to worry about it.

The major risk of an ultra-plinian eruption would be ash covering a very large area, the explosions involved would instantly crush anyone within 25 kilometer. Think a hydrogen nuclear bomb shock-wave here. Between 25 and 50 kilometers there would be an initial 50 percent mortality rate due to high aerial ash content, lava bombs, and enormous pyroclastic flows covering large parts of the Bay of Naples. After the event pretty much no buildings within the 50km radius would be left standing up. Nationally deaths would occur due to ash and gas contamination. The coming year southern Europe would suffer crop failures. There will be an increased likelihood of hemispheric rapid cooling causing additional deaths and famine.

Death rate, 100 000 to 4 000 000. Supervolcano as a term is nuisance, but if one would erupt in a population the size of Naples it would have major impact. Regardless of the term, the effect on the population of southern Europe would be truly “super”. Remember, it is highly unlikely to happen.

This was the second installment in a series that will be five posts long. Remaining are the two other supervolcanoes encircling Naples, and of course the mentioned Pompeian eruption.

CARL

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