The earthquake swarm at Arnarvatns highlands

The earthquake swarm that started two days ago at Arnarvatns highlands continues in similar manner as was seen in the earthquake swarm that took place under Blöndulón lake few weeks ago.This earthquake swarm is taking place in a fracture zone known as West Iceland Fracture Zone (WIFZ). But that fracture zone sits between East Iceland Rift Zone and Snæfellsnes volcano zone. This area is known for strong earthquakes, but in the year 1974 there was a magnitude earthquake that had the size Mb5.5 to Mw6.1 (I am not sure on the exact size of this earthquake). According to news there is speculation that this earthquake swarm is somehow connected to the earthquake swarm that did happen under Blöndulón lake few weeks ago. This area is unpopulated and several tens of km to next farm in this area.

Click on the picture of better resolution. Picture is taken from here (Icelandic).

Explanation for the numbers in the picture. The number account for the fracture direction in the area. 1: Northwest-Southwest fracture. 2: West-East fracture. 3: North-South fracture. 4: Northeast-Southwest fracture.

Where the earthquakes are currently taking place are on the west-east fractures in the area. There are no active volcano where the earthquakes take place that I know of. The active volcanoes are south and west (Snæfellsnes volcanoes) of the current location of the earthquakes.

Currently is unclear if this activity did trigger earthquakes in the rift zone. That is Thingvellir and nearby areas that show earthquakes on IMO maps. This might just be poor locations from the SIL system. It is also a question if this earthquake activity is the reason for earthquakes close to Geysir (volcano) geothermal area.

Click on the picture for a full resolution. Picture is from Icelandic Met Office web site.

The earthquake swarm at 13:10 on the 6th of December 2010. Picture is from the IMO web site.

At current time is remains unclear if this earthquake activity is a pre-events before a bigger earthquake in this area. But about ten years ago there was a earthquake swarm south of this location with many earthquakes reaching ML4.0+ in size. But in any case it is worth keeping tab in this earthquake activity, as it might signal more interesting times ahead in this area. But that is just speculation on my part. Earthquake activity might fall down to nothing (normal for this area) in a short time span.

Due to how fractured this area appears to be. I am not recording the earthquakes in this area properly, as the energy of the earthquake wave appears to vanish rather quickly due to the fractures that are between me and the earthquakes that take place (the wave energy that goes north in this case). But this was not the case with earthquake swarm that took place in Blöndulón lake.

Icelandic News of this earthquake swarm. Use Google Translate at own risk.

Skjálftahrina stendur enn yfir (Rú
Skjálftavirkni á Arnarvatnsheiði (

Text updated at 13:57 UTC on 6th of December 2010. Minor error fixed.
Text updated at 08:33 UTC on 9th of December 2010. Error fixed.

78 Replies to “The earthquake swarm at Arnarvatns highlands”

  1. Jón F – thanks for keeping us well informed on all the activity, you must feel like a ringmaster at the circus in these days!

  2. I’m always amused at the “Use Google Translate at own risk.” caveat.

    Some of the things that translator says are hilarious. Yeah… some of it is profane, but I don’t get offended by strong language. I even use it myself… generally when inadvertently hit a knuckle or get tangled up in a briar patch.

    I strongly second Birdseye’s sentiment.

  3. I have been to the Kleifarvatn/Krýsuvík area today (the photos will come later today or tomorrow). I can say that this area is much more active than the last time I have been there in july. The geothermal area of Seltun, where the old borehole exploded in ’99 shows more activity. Then there are two new hot springs at the southern edge of the lake.
    And I think the level of the lake is somewhere between 50-100cm lower than the last time I saw it. This is just an estimation from the flood marks at the beaches. This might be due to the little rainfall we had in the last weeks.

    1. Rainfall??
      so it’s not all snow?
      i’m surprised…….. i’ve had snow for weeks now.

      1. We had warm and cold periods. Actually its freezing cold (around -10°C), the prediction for the end of the week is +8.

      2. Mots Fo and Chris: I could mail you a couple of Centigrades to warm you up. It would be actually a relief, since we are hitting +36 ºto +38º C these days.

      3. Well it would be appreciated here….
        i had to take the truck in to get the heater fixed.
        My darling daughter refused to let me drive, she demanded that she drive it in and i’d pick her up….. she had to scrape the inside of the windows to see…. and it’s only 10 F out. Not even really cold yet…. but cool enough. i used to keep a handy themometer with both scales on it to reference the conversion quickly but it broke… Will have to get another….
        And God Bless the girl! the cold really hurts my heart and she saved me some pain.

      1. I got a email saying that the hot springs at the south end of the lake are not new. But they do get hidden by water when the water level is high enough.

        I also got a few pictures of the area that I am going to post next weekend. As I got a permission to do so.

      1. Genetics which predisposes one towards a Darwin Awards nomination? Seriously, while I’m quite familiar with square roots and from a philosophical point of view, what is the rationale behind the fact? Just as e always comes out the same, the fact that negative numbers do not have square (etc) roots tells us something about “reality” (a.k.a. physical universe, or dimmensional lattices) or the way the human mind perceives “reality”. Is it because the time dimmension is always positive and thus mathematics is an description of time?

      2. My entirely amateur perspective – I am far from being competent with sums – square roots of minus numbers are imaginary numbers, but real in the sense they are useful mathematically. And negative time is an established concept, valid mathematically- but not part of everyday experience. ….or are we going backwards in negative time, rather than forwards in positive time?

      3. “Is it because the time dimmension is always positive and thus mathematics is an description of time?”

        Seems to be the case on this planet but I wonder if my limited concept of “time” would remain the same (positive and linear) within a black hole. What becomes of “time” then? Does it spiral?

      4. I was being facetious.

        √-1 = i would have sufficed. (definition of an imaginary number)

        I’m pretty sure that i and j are related, j figuring heavy in real or imaginary power. “modoki” Same but different.

      5. In 5-phase time the root from any negative number would equal an fractal. Feel free to try, you just have to figure out the corresponding 11 dimensional m-set first.

        And there I went physically anal…

      6. It’s hard enough wrapping your head around Delta to Y configured transformers for 3 phase…

  4. *Trying to catch up with all the news, and having the feeling I’m running behind the facts and never able to get there *

    Thanks Jon, for your work and dedication!

    1. That happened to me on the Eruptiosn Blog from Erik Klementi, i lost track somewhere around the merapi eruption, it just got to bussy over there 😉 at least here its possivle to get up to date without getting lost in the threads. 🙂

    1. Perhaps we should set up a rule that caps with hundreds of exclamation marks to be reserved for announcing new eruptions in Iceland. Bank run does arouse in me nothing but a shrug and a yawn, but my first reaction upon seeing so many exclamations was as if Katla had broken loose.

    2. Here we don’t care about bank runs (At least I don’t). Unless they are being over run by lava or ash. But that is not the case here. So just don’t post this again.


  5. Ok, I was looking at the lake near Krisuvik when I saw this feature. Can anyone explain to me exactly what it is?

      1. You mean this lighter area? I think thats just sediment, which is carried into the lake. This is the southern end and exactly where I was taking photos yesterday. A small river leads into the lake at this point. You can see the lake in this photo:,+Island&sll=37.0625,-95.677068&sspn=51.355924,89.560547&ie=UTF8&hq=&hnear=Kleifarvatn,+42,+Island&ll=63.909142,-22.010615&spn=0.007031,0.021865&t=h&z=16

  6. Tyler- looks like shoaling to me, caused by currents. Had to deal with that on the
    Oregon coast, especially around some of the US Army Corps of Engineers
    breakwaters and docks Like Port Orford…

  7. There are indeed three areas of interest in Iceland at the moment which is VERY clearly shown on the map below.

    Could they have any connection with eachother? What I mean is that if there is a large tectonic strain underway could this be the result?
    If so is this just a way for the plate boundaries to release pressure or is it building up to something bigger?

    1. This is not the reason for this. As the east and the west rift zones are not directly connected. But it is a question if the activity north of Langjökull signals a new period of activity in that region. But it remains to be seen what happens next in that area.

      The Krísuvík activity is most likley due to magma intrusion.

      1. What strikes me about the recent areas of activity is that the earthquake swarms seem to be stretched out as if along a fault line. As has been said earlier, the void between the diverging plates will be filled with magma, the only question being if the subsequent splitting at the surface will result in central volcano eruptions (Eyjafjallajökull, Katla), fissure volcanoes (Krísuvík, Hekla) or fissures (Laki, Eldgja). Somewhere, the surface will have to split at some point in (geological) time and before that, somewhere the magma will break through first.

        Iceland really is unique!

      2. In most cases these ‘gaps’ are filled by dyke intrusions which never reach the surface.

      3. From Global Techtonics, 3rd ed

        … At any depth, deviatoric tension can cause yielding by faulting, ductile flow, or dike intrusion, depending on which of these processes requires the least amount of stress. For example, if a magma source is available, then the intrusion of basalt in the form of vertical dikes could permit the lithosphere to separate at much lower stress levels than is possible without the diking. This effect occurs because the yield stress that is required to allow basaltic dikes to accommodate extension mostly depends on the density difference between the lithosphere and the magma…”

      4. I have a different theory all together on that. I actually think that for once there is actually a link between the Askja/Herdubreidartögl acticity and the Krysuvík action compared to the activity at the Western zone.
        I will prepare a longer post on this in this thread.

      5. Well, keep in mind that the many of those quakes sort of line up in a plane canted at 62° from horizontal, oriented at 241º 61º at the surface.

      6. Well.. roughly speaking, they are at three of the four corners of the Hreppar microplate’s psuedo-parallelogram. Katla and little sis being near the other corner.

      7. Lurking, you see what I mean… Never explain what you want to say when tired.
        I even forgot that one…
        It is thusly 3 corners that are inflating, even not counting the former inflation at Eyjafjallajökull we still have the inflation at Godabunga. So 3 inflation engines running now.
        Wonder if “the Northwest of Langjökull” (forgot the name) is also inflating?

  8. Peter, Sigrún, love the discussion! As I understand it, time is a measure of change. At 0 Kelvin, time ceases as particles cease to move, i.e. there is no entropy, and I’d imagine the same applies to matter beyond the event horizon where not only time, but also space (i.e. dimmensions 1-4), cease to exist. It’s just too hard for the brain of a four-dimmensional creature to encompass the full ten dimmensions postulated for the Universe.

    Perhaps science is the more limited of the two disciplines; science and philosophy as the latter better explains phenomenae “outlawed” by science such as imaginary numbers and deities?

    1. Imaginary numbers are not philosophy, but mathematics, i.e. hard science. And any deity being describable is not a true Deity, but a human idea. The definition of a God or Deity explicitly denies complete description.

      1. This is true, but it is also true that it is impossible to prove the existance of one’s mind/consciousness using mathematics/physics/science and that the only available proofs of mine and yours is philosophical. Imaginary numbers is where mathematics – to its great credit – has stepped out of science and embraced philosophy and thus gained valuable insights.

      2. I’d like to second your opinion! Imaginary numbers are not “just a philosophical extension to mathematics”.

        Just take Euler’s formula or any four-momentum space-time presentation (with time as the imaginary part) to see real applications of imaginary numbers with a well-defined mathematical/physical interpretation.

    2. “The definition of a God or Deity explicitly denies complete description.”

      But are not mathematics and the physical sciences partial descriptions of how “God or a Deity” brings it to pass?

      1. Ok, maybe to a very limited extent.

        But: I also do think, that no science, nor philosophy can offer any significant proofs for existence/non-existence of any kind of true God or Deity (if there is One).

        And the history of science has shown that it’s better not to try to proof something non-existent, as it usually has turned out to be the other way round.

      2. You’re right. Whether or not one chooses to believe in the existance of any deity is a matter of belief and this is why atheism too is a religion. It is only if you take the agnostic approach that you are able to retain scientific objectivity.

    3. New Scientist 4 Dec has article about temperatures below absolute zero….when a rise in temperature decreases entropy.
      Not sure about time ceasing at -173C; motion can only be measured in time.

    4. Sorry, time is not slowing due to temperature. What we perceive as time = particle movement, slows down with lower temperatures. Problem is just that there is no real equal sign between particle movement and time. Time doesn’t give a figs mint about if a particle is at a stand still, if it did we (the observer) would not be able to observe that one particle (A) is at a standstill compared to equidistand particel (B) in motion. That would be clear if we decided that we also where a particle (C) that is also at a standstill. Since we then either can not observe due to time standing still, or out of us being frozen in motion we get a value-tree. If C is frozen in time we have varying times for all three equidistant particles and if C is frozen in motion we have the same time, but it will apear as 3 different times relatively speaking.
      What on earth does this have with anything to do?
      Well… We know that if we have 2 atomic clocks the one in a higher G-state will move slower than the one in a lower G-state. Most believe that it implies that the time is slower in high G. Correct? No, actually the gravity just makes the atoms move slower in the same time-frame for the gravitetically challenged atomic clock.

      Sorry, this is wastly dumbed down, so it might be a bit unclear.
      For those who want the full math for it I recomend reading the Schwarchildt and Rosen papers on the “Schwarchild-Rosen Bridge on time dilation” (Heavy black hole theory…)
      After that read Edward Fredkin “Digital Mechanics” and the break-through paper “Digital Philosophy” to understand 5-phasic time. If your brain is still intact after reading Fredkin you are insane, if it is not intact drink an all-galactic gargleblaster, preferably before reading. Deap shit warning!

      1. And before anyone has a mental breakdown 🙂
        I set you up on this one…
        Time is a universal constant = C.
        The sum of a particles speed is always C, the sum of the motions involved will always end up as “that pesky” C in relativistic space. Therefore C is the constant of motion in relativistic space and at the same time it is the constant of time in quantum space.
        The effect of this is that if time slowed in quantum space a particle (super-string) would change it’s size if time was not a constant. As par example an electron string was closing in on near zero Kelvin, and it’s time mysteriously slowed in quantum space, it would grow exponentially in size untill it become bigger than 1 quantumlength. At zero Kelvin it would be huge. Since this provenly by non-observation is not happening we can safely say that A) the sum of all the particles (strings) speeds are C even at zero Kelvin and that B) time is a constant in quantum space.

        I still recomend reading Fredkin after having a big whopping all-galactic gargleblaster.

      2. Carl, there is an error in your logic: For you, the observer, and the remainder of the universe time flows when you observe the particle at -273.15 degrees centigrade or 0 degrees Kelvin. For the particle in question hovever, entropy has ceased and time is at a standstill. In a sense, there is an event horizon here too as the gradient where the temperature rises above absolute zero also signals the return of time. 😉

      3. No Henrik, for the particle IN ITSELF (not angry, just pinpointing the logical crucible) still has the SUM-SPEED of C at zero Kelvin after counting all the speeds at both RELATIVISTIC and QUANTUM motion.
        This is an error that is normal due to the INTERSTICE

      4. (Continuing here since the hatefull windows-button hi-jacked me…)
        …INTERSTICE between relativistic and quantum space is poorly known due to lack of a GUI. But the particle speed constant is known since ancient times.
        Let us look at it as this.
        Take an electron in hard deep space, even though it is travelling in +2,2 Kelvin it still has the full C as particle speed. Since an electron travells in all possible paths at the same time the sumed speed would be C (Feynman & Gibbs; Quantum Mechanics & Path Integrals)
        Your logic is flaved since you aparantly do not sum up all the speeds a particle can be subject to.
        There are a heck of a lot of particles out there travelling at close to the speed of light that is subject to near zero Kelvin, and they still travell on.

        I will try this a different way since we are talking about a fundamentally very hard subject to understand.
        The effect you are talking about is only existing in relativistic space, at the quantum level you have energy EVEN THOUGH it is at zero Kelvin in relativistic space. In the quantum space you have bucket loads of stuff going on still, quantum foam in form of particels and anti-particles coming into existance and going out of existance just to take an example. The particle/antiparticle duality is mathematically proven for black holes by Hawking where particle/antiparticle creation/anhilation is actually creating heat affecting both at quantum level and on relativistic space. The effect on the later being minute though, but it still creates time and temperature to black holes. See where I am going?

      1. Thank you! May I say likewise about everyone on here and definitely so in comparison to most of the people, bless them, I encounter daily?

  9. M4.8 EQ at the southern part of the Reykjanes Ridge, I wonder if this will result in another swarm near the coast of Iceland.

  10. @all (and Jón above)
    As some of you remember I half a year ago used some heavy fluid dynamics applied onto Iceland and came up with something I called a Vortex theory to try to explain what is going on in Iceland. Problem was that I was not good enough back then in geology, volcanology and soforth. Ie, I was wrong. But, the math was correct still.

    What does my flunked theory has to do with what is happening on Iceland today?
    Well, it mathematically predicted that corners of sub-plates where natural corners of activity. And that with mathematical validity under certain premisses.
    1. Lateral movement apart between sub-plates. Ie, that two sub-plates are moving away from each other as oposed to them sliding next to each other.
    2. Sideral movement. Sub-plates sliding next to each other.
    3. Inflation occuring at one of the corners.

    I am not going to refer to all of the places where we have instances of 1 and 2, those have allready been stated in links and posts while I was gone.
    What has happened is that we now have inflation at the Krysuvík and the massive Askja/Herdubreidfjöll (With Grimsjöll and Bardarbunga creating nice premiss 1s).
    This creates an uneveness in motion that forces the corner up to the northwest of Langjökull and Northwest of Hofsjökull. At the same time you get a forced instance of premiss 2s happening towards Grimsfjöll. So for once there is fluid dynamic reasons for all these things happening at “the same time”.

    This activity is releasing a lot of pent up energy which will show up sooner or later as increased movement between the plates. But we at the same time we have the problems with the quake-dead areas where the crust is more pliable. And here the energy instead builds up quickly now. And we are here talking about areas like Laki, Elgja, Veidivötn and so on.

    I see the potential for 3 things that can happen.
    1. One of the volcanos that is being inflated erupts in the not to distant future (withing 10 years). And that would be Krysuvík, Bardarbunga, Grimsvötn, and Askja.
    2. Large fissure eruption at one of the quake-dead areas.
    Remember that both a central volcano and a large fissure eruption can happen at the same time or almost.
    3. This is what is starting to worry me. We also have seen a small but still distinct number of quakes starting at 2 volcanos considered as extinct. The first one is Esjan who haven’t erupted in the central volcanic area for 1,6 million years, but had a fissure eruption at Raudholar 4800 years ago. The quakes have been under both Esjan and Raudholar in a line following the old almost extinct western volcanic zone. Any activity here would be catastrophic for Iceland since this is pretty much in downtorn Reykjavik. The other one is a forgotten piece of Icelandic big-momma volcano, Theistareykjarbunga. It last erupted 2900 years ago, but it once had the largest confirmed known lava eruption of all of Icelands volcanos when it it one go ejected 30 cubic kilometres of lava and equal amounts of tephra when it in one go built the Storaviti shield volcano (Theistareykjarbunga central volcano) 12000 years ago. As far as is known it has only had 3 eruptions, and is quake-dead up untill now. It is the northernmost volcano leading on the Askja/Krafla/Theistarykjarbunga line leading up to the Tjörness Fracture Zone. Ie, what I am afraid of is that Krysuvík might be ripping up the WVZ (Raudholar) or Askja ripping up Theistareykjarbunga. The reason for this would then be the large pent up forces from the inflated movements at 2 of the sub-plate corners.

    To get how bad Theistareykjarbunga is… It has erupted larger than Laki, Veidivötn and Eldgja fissure eruptions put together.

    Sorry that I could not explain myself better, I have just landed after flying from Etna and tried to read up on all the action since thursday morning. Whew, you guys got the action, I just got a mast to deal with on my boat.

    1. Okay.. this is for everyone who has asked what a Laki style event might have as a precursor.

      Ellen Schaal (who I have no clue about) authored a day guide for a field expedition/trip (for students I guess) titled “Lakagígar: The Craters of Laki”.

      The link (after prying it loose from Google claw like grasp) It’s an FTP link, but you should be able to right click it and “save as.”

      From the guide:

      “The first signs of an impending eruption at Laki were weak earthquakes that started in mid-May of 1783 and intensified in the coming month. Then on June 8th, a dark volcanic cloud spread over the region, and ash began to blanket the ground… …The explosive episodes were followed by long phases of Hawaiian-style fire-fountaining… …the Grímsvötn central volcano erupted at least 7 times in conjunction with the Laki eruption, suggesting a major volcano-tectonic episode on the Grímsvötn volcanic system in 1783 and 1784.”

      So.. there was about a two to three week run up of quakes prior to the eruption. Quakes that were noticeable to someone tending a field or minding a flock/herd… or at least noticed by people in the area with no specialized equipment.

      1. Ahhhh thanks for that… I remember reading this, and was looking for it to post to this thread. Well done for finding it!

        ‘Weak earthquakes’ would mean ‘weak but perceptible to humans’ remember, so I’m guessing we’re talking M3-4…?

      2. @Fireman

        “‘Weak earthquakes’ would mean ‘weak but perceptible to humans’ remember, so I’m guessing we’re talking M3-4…?”

        That’s what I’m thinking. Any thing smaller and you’d probably have to be be sitting on top of it to notice… capable in being measured in “Big Mac” energy equivalence.

        So… not seeing a persistent run up like that means that something of that scale is out of the question. But we have an idea of what it might look like.

        Too bad the only thing resembling a modern seismograph came 100 years after Laki.

    2. Oh yeah.. it’s has some really nice maps of the flow and how the rootless cones were formed.

    3. To make one thing clear. Esjan is extinct and is not going to erupt again. Any volcano related activity close to that mountain is going to come from the active volcanoes on the Reykjanes peninsula.

      Þeistareykjarbunga is not showing any signs of activity, same as for the last 200 years or so. If Þeistareykjabunga erupts it is not going to be any more damaging then when Krafla erupted. But effects depends on the volcano it self. Currently there is no reason to worry. The volcano is dormant and until that changes there is no reason to worry about it.

      There are going to be pre-events before a fissure eruption. It was seen before Laki eruption by the people how had no instruments at all (historical data). We the people how have instruments are going to detect the changes months and months in advance and manage to give and warning and prepare for the impending eruption before it takes place.

      I do believe that Rauðhólar are from Brennisteinsfjöll volcano. That volcano has not shown any signs of activity. But there are a lot of tectonic earthquakes there. More information on Rauðhólar,

      Volcanism in Iceland,
      Brennisteinsfjöll volcano,

    1. If I just get some sleep I will reason better. I am not entirely satisfied with my try at explaining what I meant…
      I am tired after my venture to Catania, and the entire trip was you fault Renato. All that talk about beautifull women at beaches in warm weather forced me to go and sail in the mediterranean. Sadly Etna was quiet.

      1. Hehe! Not exactly the right season for sun and women with all the cold waves affecting Europe.
        But the visit to Sicily brought you back very inspired.
        @Lurking: Thanks for the article on Laki. This will be my weekend’s entertainment. I am sure Carl will love to take a look at it as well.

      2. Nah, it was pretty warm down in Sicily. At least it was above 20C during the days. When coming from -25C that is a massive heatwave…
        Yepp, I will read it during the weekend.
        Now I have to get some sleep before receiving 1 ton of oddly shaped aluminium in the morning… 🙂

      3. I’ve been to Catania in the winter. Spent most of the port visit in search of bars. The stop I did in Haifa I spent most of the time avoiding the dog near the berth. I had never seen a dog bite a fender before that.

      4. @Lurking: LOL. Flying pigs, barking dogs. This is Lurking.
        @Carl: Maybe you weren’t lucky with Etna, but the weather has been fair to you. Never been to Sicily, but often at Rome, and I heard that it can get really cold down there, at least in a couple of occasions when there was snow even in Athens, Greece.

      5. I must admit that there was some soulsearching in bars going on…
        But mainly I had to wrestle with a muscle-winched mast-winch to exchange my broken aft mast.
        A 1 hour operation with a proper winch took all day. It didn’t even have a stopper on it so I had to hire a kid to stand and hold the winch while I screwed down the wires.

      6. Welcome back Dr. le Strange! And thanks for the wealth of info (your prolific comments) which I shall thoroughly enjoy investigating.

  11. A whole lot of shaking going on …. As usual, my! How you Icelandix have an exciting time and keep your cool in the meantime beats me, living in the grey wasteland as i do i often imagine what it’s like otherwise. Thanks for the lively info and regards to (you) J F for the provision!

  12. Lurking, there is another occurance of isolated clusters focused within a 1km area in brawley, ca. These are not that uncommon especially recently with all the activity since April 2010. In light of this, the article below caught my eye. Could it be that the stress waves along the tectonic boundary are also moving upwards into what I believe is the \Brawley Fault\ which is hypothesized in this article to be connected to the southern tip of the SAF? 66 (4)/1133.pdf

    1. Cant get to the article.

      But I think that the wave that I had tracked is lost in the rubble of Southern California. Can other’s impart energy to the rubble? Yes. But I don’t think that locating where it is at, or should be, is possible. During the last few months of it’s trek, it seemed to slow in forward progression. This makes sense when you consider that whatever it would impart is spread across a lot of different blocks and fault lines. By this time, if everything was linear, it would be almost to San Fransisco.

      Brawley has the honor of being part of the melange of SoCal. Lots of different provinces, the Basin and Range being the other dominant thing near there. FYI, the Basin and Range is a spreading area, but is different from Iceland in that it covers a comparatively HUGE area. This makes it’s mechanics a bit different… plus there is no plate boundary there. Graben and horst is the primary mechanism… along with some transforms here and there. That in of itself causes a lot of activity in seemingly unrelated areas.

      Here is a graphic from Global Tectonics 3rd ed. that might serve to illustrate just how complex it is there. And it doesn’t even show the various crust blocks from Gulf of California to North of LA, and there are a lot of them.

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