The Aniakchak Earthquakes

Photograph from New York Times. In the image we see the massive crater wall and two of the rebulding vents. Well worth to click on the image to watch the full size.

Photograph from New York Times. In the image we see the massive crater wall and two of the rebulding vents. Well worth to click on the image to watch the full size.

Few of our readers have missed the anomalous M6.2 earthquake that occured 20 km WNW of the Aniakchak Caldera. In this article we will go through the details of the earthquake and the possible effects of the main-shock and the series of after-shocks.

Graphic from EMSC-CSEM. Beachballs for the earthquake.

Graphic from EMSC-CSEM. Beachballs for the earthquake.

According to the Alaska Earthquake Center the waveform of the initial 6.2 was hard to calculate correctly and it initially looked more like several stacked earthquakes at the same location. This postponed the release of the earthquake data from both AEC and USGS with several minutes. In laymans terms, this earthquake started and almost halted before picking up speed again making it look like it had individual sets of P and S waves.

The initial earthquake followed the main stress-regimen of the subducting Aleutian arc which is common in the area. What was unusual was the depth of the earthquake. As you get further north from the faultline the depth of the earthquakes increases, near where the subduction starts the depth is normally around 20km and as you get further back they become progressively deeper until they reach 80 to 120 km depth around Aniakchak.

This earthquake was at 20 kilometers depth and this is the first earthquake at that depth recorded in the area.

Historic beachballs for the area for comparison. Graphic from EMSC-CSEM.

Historic beachballs for the area for comparison. Graphic from EMSC-CSEM.

All available evidence that we can see points towards that the large quake and the ensuing aftershocks are part of the accumulation and compression of material in the accretionary wedge. If there is an eruption, it will (in our opinion) be due to an existing magma chamber getting over-pressurized from the new increased compression stresses following the compaction driven quake. The moment tensor for the large quake clearly points to it being reverse mode faulting. Similar to the main subduction fault, but shallower, indicating that it’s likely stuff being piled up on each other.

Other systems like this are things like the entire Eastern coastal shelf of Japan, The Kamchatka Peninsula etc…

The main quake was probably along one of the area’s accretionary prism thrust faults. The M 6.2 quake had a dip angle of 49° for the NP1 plane and 42° for the NP2 plane and that fits our idea. Doesn’t prove it, but it fits. It also dovetails quite well with the observation that the M6.2 could be an aftershock of the 1964 Alaska quake since this is trending towards the area where that fault system petered out when it ruptured. Everything we are seeing now is related to the strata adjusting to the new stress regime.

ANPB station, graphic from Alaska Volcano Observatory. Initial earthquake and following after-shocks.

ANPB station, graphic from Alaska Volcano Observatory. Initial earthquake and following after-shocks. Note that the waveform looks like stacked earthquake, but in reality was one discrete earthquake in sequences.

Again, it’s just our opinion, but there will not be an eruption unless existing magma is re-mobilized from the new compression stress pushing a chamber over some critical pressure, sort of stepping on a mustard packet. And like mustard packets, it could be quite energetic if that happens. That could even be the same mechanism that originally made the caldera there. A massive pressure increase, really really fast that blew out the chamber of a previous volcano.

Now that I think about it… that could be what’s at play in New Zealand when those systems go nuts. The quick pressure rise and blow-out would help explain how Taupo was able to have almost no zonation in one of its eruptions. Everything went off at once when the lid let go. It would also help to explain how that area can have such rapid dike emplacements. I think I’ll call this the mustard packet scenario.

Conclusion

Image from the Alaskan Volcano Observatory. The continuation of the after-shocks as it turned into the Harmonic Tremor event related to the Aniakchak Caldera. Image grabbed by Michael Ross.

Image from the Alaskan Volcano Observatory. The continuation of the after-shocks as it turned into the Harmonic Tremor event related to the Aniakchak Caldera. Image grabbed by Michael Ross.

The tremor that is being seen on the local seismometer network in the area and that has been felt in Port Heiden by the village council is likely to be the magma chamber under the Aniakchack reacting to the new stress regimen.

Also, there is a marked resemblance to what was reported from Port Heiden prior to the 1931 eruption with written reports of earthquakes and volcanic tremor being felt there. For those who are not familiar with Aniakchaks eruptive history, this was a borderline VEI-4/5 eruption scoring in at 0.9 cubic kilometers of ejecta.

So even if this was not a volcanic earthquake swarm as such, the vicinity and relation to the general stress regime and the accretionary prism in combination with the tremor could over time affect the magma reservoir in the nearby Aniakchak Caldera. If it would lead to an eruption is an entirely different question and if that happens we will have reason to return to the largest volcano in Alaska.

CARL REHNBERG & GEOLURKING

141 thoughts on “The Aniakchak Earthquakes

  1. Every time I browse through the AVO webicorders it looks like the whole area is very active. AVO must have plenty on their plate.

    • There are also bucketloads of storms disturbing the seismos.
      It is hard to spot the minute things in advance that are necessary to spot to predict eruptions. And it is also hard to find the GPS data for most volcanoes, if there is even GPS data.

  2. A tip to “monitor” Alaska volcanoes, “Swarm” is great tool to access seismometers data. Requires JAVA.

    http://volcanoes.usgs.gov/software/swarm/download.php
    Unzip it, go to folder and double click in “swarm_console.bat”

    Example

    To analyze using other software (ex: Seisgram2K), i recommend downloading the seed file from IRIS:
    http://www.iris.washington.edu/bud_stuff/bud_dir/AV/
    Just go to station folder and download the SEED file.

    A lot of seismograms have “spikes”, making very difficult to extract anything.

    • A good tip, we will probably put it in our good tip page or something. 🙂

    • Thanks very much for this!

      By dialing the graphs you can definitely see what is signal noise and what is tremor. They are very noisy but it comes and goes in intensity

  3. Carl,

    There seems to be a fair amount of water in the area, do you think that with all this movement something could be triggered by water/magma interaction?

    • It is quite possible, there are loads of evidence of hydrothermal, phreatic and phreatomagmatic activity in Alaska. Among them quite a lot of Maars. Also, the magmas are often high in water-content.

  4. Really surprising ,that alert level did not go up a notch,if there was volcanic tremor in a system that has been relatively quiet for decades?Particular after a nearby significant earthquake.

  5. not sure if its of any importance, but nonetheless, this is depth to MOHO, from GOCE/GEMMA data.

  6. “That could even be the same mechanism that originally made the caldera there. A massive pressure increase, really really fast that blew out the chamber of a previous volcano.

    Now that I think about it… that could be what’s at play in New Zealand when those systems go nuts. The quick pressure rise and blow-out would help explain how Taupo was able to have almost no zonation in one of its eruptions. Everything went off at once when the lid let go. It would also help to explain how that area can have such rapid dike emplacements. I think I’ll call this the mustard packet scenario.”

    I’ll bet dollars to doughnuts that this is the trigger mechanism behind *all* super-eruptions. Think about this: there is no supervolcano that is not in an area riddled with thrust faults and prone to reverse mode faulting. Most of the caldera systems with a history of VEI7+ events are on subduction arcs, where they’re subject to the same mechanism as this Alaska quake; Campi Flegrei, with a history of VEI7s, is on the edge of the Mediterranean whose entire basin is being slowly compressed out of existence by Africa and Europe pinching it between them; and Yellowstone, the odd one out in having a hotspot as its magma source, is in the middle of the Rocky Mountains, which are fold mountains that are still growing due to compression of the region. In every case I’ll bet some tectonic motion in the region affects the magma chamber like squeezing a pimple until the top pops.

    If you check the history of the Yellowstone hotspot, when it was strictly between the coastal subduction zone and the Rockies it produced flood basalts rather than high-VEI explosive eruptions. It switched to ultra-violent eruptions when it reached fold mountains. The mechanism behind that is clear. Hotspots usually dome the crust up above them, which creates extensional stresses. Magma easily reaches the surface before undergoing much evolution, and emerges from extensional fissures as juvenile basalts, producing Hawaii and Iceland type red eruptions. Move the hotspot into an area that’s being compressed tectonically, and this overwhelms the doming. Magma’s path to the surface is slower and more difficult, giving it time to evolve towards rhyolite, and thrust fault earthquakes can suddenly pinch the magma chambers, setting off large gray eruptions. So, before the Yellowstone hotspot got into the Rockies you got things like the Columbia River flood basalt and the Steens flood basalt from it; after, you got things like the Arbon Valley Tuff B and the Lava Creek tuff.

    • You’re jumping to a LOT of conclusions here.

      “Most of the caldera systems with a history of VEI7+ events are on subduction arcs, where they’re subject to the same mechanism as this Alaska quake; Campi Flegrei, with a history of VEI7s, is on the edge of the Mediterranean whose entire basin is being slowly compressed out of existence by Africa and Europe pinching it between them”

      You’ve basically just described every arc volcano in the world – very few of which are large or supervolcanoes. This doesn’t really say much to prove anything. Most explosive volcanoes in the world are within subduction arcs, but the reason likely doesn’t have much to do with compressive stresses caused by accretion. The reason volcanoes in subduction arcs are often more explosive is that they assimilate some of the crust when magma rises, and there tends to be more volatiles in the rising oceanic basalt that comes from oceanic plate subduction. These two processes result in more gas-rich magma than you see in a place such as Iceland. Also, continental crust tends to be stronger than oceanic crust, which can withstand higher pressure, allowing for large, and highly pressurized magma chambers to develop.

      Also, one important element in many of the world’s “supervolcanoes” is actually the opposite of what you’re mentioning. Instead of compressional stresses, decompression and rifting is a more common component in enormous volcanic systems. The Taupo Volcanic Zone sits on top of a subduction arc, but also sits on top of an area where the crust is spreading apart. Toba sits in a transverse fault that likely has some degree of localized spreading where it’s situated.

      Now, I’m not saying an earthquake that compresses a magma chamber couldn’t shake up or set off a volcano, but I strongly doubt it’s one of the primary causes of supereruptions.

      “If you check the history of the Yellowstone hotspot, when it was strictly between the coastal subduction zone and the Rockies it produced flood basalts rather than high-VEI explosive eruptions. It switched to ultra-violent eruptions when it reached fold mountains. The mechanism behind that is clear. ”

      The rocky mountains and basin and range province are not compressing, they’re actively decompressing after being compressed millions of years ago when they were originally created. With that said, you’re probably correct in that the strong and thicker crust it sits over right now is likely **part** of why it erupts in such large volumes.

      • Magma in Iceland seems to be very gas rich?Maybe what makes Iceland different is eruptions occur much more frequently(due to a very shallow crust),giving less time for very large emplacements of high silica magmas,such as rhyolite to form.The Taupo volcanic zone has far few eruption episodes in say a thousand year time period and hence very large accumulations of rhyolite are present.Yellowstone is even more infrequent and so it is a massive accumulator of evolved magma?The key maybe is the ability of the crust to accumulate and evolve magma and the frequency of the basalt trigger(the breakout of a large volume of primitive magma to shallow depth in the crust at one point of time),that trigger being frequent in Iceland and quite infrequent in New Zealand and at Yellowstone almost non existent?

      • In the original idea, a note given in the back channel during article prep, the squashed mustard packet idea was just a thought, not a conclusion. It came about from me getting a hamburger and inadvertently spraying some guys car when I stepped on one. Dunno what was inferred or derived from the idea, but was just an idea. AS A RULE, there are going to be a lot of random variables that ultimately determine if the mustard packet scenario actually plays out.

        And likely, as is true in many many cases, the truth lies somewhere in between.

        • Tarawera was a “mustard packet” if you like,2 km3 of basalt erupting through a 17km long fissure in a less than 4 hours, but it possibly passe through the rhyolite lean spot and ended up an enhanced basalt eruption rather then a massive rhyolite caldera event.Holuhraun was a strangulated mustard pkt ,erupting nearly as much, 1.4 km3 but over the course of many weeks so even if there was somethng to trigger ,it bypassed it and the rate was too slow to be a trigger for it anyway,other than a more modest eruption?

        • Actually, Holuhraun was the reverse side of that action. The spreading plates lowered the confining pressure on the rock and allowed the existing pressure in Bardabunga’s chamber to more easily penetrate the rock. That drop in confining pressure in essence, lowered the hoop strength of the chamber’s walls.

          In either case, when the pressure in the chamber is above the mode 1 failure stress that the rock can withstand, the dike propagates. Below that, the dike slams shut.

          I don’t have the actual details, but I think the hoop strength is roughly the rock tensile strength + the confining pressure (from the overburden)

          As for the Tarawera mustard packet. I think that was the actual case.

          Heh, fitting…

          https://en.wikipedia.org/wiki/Lake_Rotomahana

          • Haha, you found a pic of a black swan on Rotomahana! 🙂

            Yes, Lurking did in dead caveat it in the back channel, but it got lost in transferal when I edited it in. I do though think that in some instances the Mustard principle is correct.

        • Hi, Lurk! i’ve been busy of late; just wanted to say it’s always fun to read You. Best!motsfo

      • I think that even in the Great Rift Valley in Eastern Africa there were VEI 7caldera forming eruptions in the past. Also because of the thick and strong continental crust, allowing big magma chambers to form, and rising magma which assimilates continental crust too. In general with volcanism on thick continental crust it doesn’t matter from which the magma comes from, whether from subduction, or rifting, or a hotspot. In all cases volcanism on thick continental crust tends to be explosive.

        • Yes, as the african plume hit the craton it caused several very large eruptions in the VEI-7/VEI-8 range. Among them what could be the worlds only VEI-8 Maar event. The only feature though that is a true supererupter is Lake Turkana.
          (Here I am talking about the southern end of the plume swath)

          • Yes there is, the Ngorongoro is wrongly attributed to being a volcano that went caldera. Instead it was a phreatomagmatic event. If you look at the flow sheet it is pretty apaparant that the ejected rock was heavily hydrologicaly altered as it was deposited. It is not an ignimbrite, it is mudsheet.

          • The Awasa caldera is fairly enormous as well. Not much documentation on it I could find, but 30x40km would put it within range of being a potential supereruptor.

          • How would there be enough water for Ngorongoro to be a massive phreatic detonation? I would have to imagine this would have only worked if there were a large lake or inland sea situated over where the ancient Ngorongoro was?

            The problem with that idea is that the idea of an inland lake or sea above Ngorongoro doesn’t make sense since the area has a higher elevation similar to a shield volcano. And as I see it, in order to get a hydromagmatic event of that scale, wouldn’t that pretty much be a requirement? I can’t imagine this all just occurring from the normal water table in the area, but what do I know.

            Maybe the caldera already existed when the deposits you’re referencing erupted? With a very large caldera lake occupying the crater, that could have created a massive phreatic detonation.

            Interesting nonetheless.

          • Then again, I look to the south and see lake Eyasi, and Natron directly to the north. And perhaps the eruptive deposits created the surrounding shield-like formation, so I guess I shouldn’t rule out the idea that it was just a long lake area in ancient times. Perhaps what used to be that lake later formed into a sort of phreatic pyroclastic shield?

            Thinking out loud here a bit 🙂 .

          • When I was there I was surprised at seeing it myself.
            I have a theory, and that is that there was already a caldera there that was filled by a lake and that had a hydrothermal event that in turn covered the first ignimbrite.
            It is a very weird place.

  7. I’m going to fly an off-topic kite here. It might be mildly controversial but it’s been nagging at me for some time and it’s this: why am I about the only person who posts under their full real name?

    I’ve been on the internet since before the Eternal September (Google it: a long time ago!). In the old tradition of internet discussion to which I belong, people always used their own real names – unless their were very real and pressing circumstances which made this impractical (e.g. posting from under an authoritarian regime or on very controversial topics). Anyone who didn’t use their real names was perceived as being a bit silly or self-important or just juvenile; either way their contributions were given little consideration.

    Yet here on a small and entirely uncontroversial volcano discussion groups almost everyone – administrators, regulars, and visitors alike – seems to feel they have to post under a pseudonym. I find this very odd. So…

    – If you post under a pseudonym, why do you do so?
    – Do folks think this should become a ‘real names only’ forum?

    I’m not shit-stirring or trying to start some kind of controversy; I’m genuinely curious as to the situation.

    • A pseudonym,makes it less personal,this a discussion area of a blog,I do not need to know your name and you do not need to know mine,what is gained by you needing to know my name unless I claim to be something I am not,which I have never done.Having said that I appreciate your openess and courage in using your own name,but also you do have some credentials to back up the use of your real name ,which I do not and hence I prefer the privacy and the distancing I can give this discussion from my real life.That is just my thought on the matter others may feel differently.

      • Geyser,

        First I don’t see the slightest “courage” involved in using my own name! As I said – to me it’s something that’s entirely normal; I would feel very strange NOT using my own name in such a situation.

        Second “credentials” are not required; yes I have a degree in geology (although I’ve never worked professionally in the field) and yes I’m an eruption-chasing professional cameraman who has been paid to film volcanoes up close and personal – but there are many here who have no qualifications and are entirely amateur armchair volcanologists – but have more in-depth and specialised knowledge than I do. The only ‘credentials’ anyone has here come from what they post. It’s irrelevant; you don’t *need* any credentials; you just need to post sensible and interesting stuff.

        • I will also add ,that because you put yourself out there in terms of identity disclosure,it will tend to make you more sensitive to any critique of your views and trolling ,as you then have to defend your full reputation rather than defending just your discussion group identity credibilty.Apart from the privacy aspect,that is the main downside of using full identity disclosure,the difficulty to achieve some distance from any perceived criticism.”Perception” is the key word on the Internet because of its instant impersonal nature,it is hard to put comments into context e.g. did that person really mean to be that rude or was that just my own sensitivity making more of it than it is?

        • Its rather easy to get personal attacks, email denial of service and false statements falsely accusing you of all sorts of things which may impinge on you and/or your children. These are hard to remove. Admittedly more if you post in areas with nutters, feminism, animal protection and so on than here. None the less you would be unwise to expose your real persona on the net.

          In science its a bit safer, but none the less this has had unpleasant consequences for several highly esteemed scientists who dared to tell the scientific truth rather than tow the political line.

          You never know, your real name is best concealed. Been there, done that.

    • Pseudonyms add a layer of anonymity. The same reason that IPs are not posted. No, it’s not for any self importance, but putting personal info out there just adds more data that a scavenger can accumulate, for whatever reason. Be it a way to run a scam, or just to try to pass themselves off as you. In online gaming, it is not really common to even have the ability to use a full name, and it’s quite possible that you can really tick some juvenile entity off quite well. (I’ve done that many times) So much so that they desire to “get even” in a real world context. As such, I am quite comfortable in not using an actual name. On the admin side of things, the people that need to or have a legitimate reason to know who I am, do. That way I can more easily vouch for myself and who I am should my posting account become compromised. The name I use reflects my persona. Some guy lurking on the internet…. yammering about geology. Here, my persona is recognized, and my reputation is known from the posts I have made.

      • Yes I agree,I used my real name on facebook,and had some person with obvious hacking ability go nuts on me, scary stuff ,never will use my real name on Facebook or any Internet discussion again.I can seem foolish at times and be aggravating to some but I never intentionally try to antagonize anyone beyond a point of no return,another point to remember,when you say something in hindsight that is unwise online,it is next to impossible to walk it back, there is no context in this realm.

        • Well Facebook is a rather different kettle of fish; there you’ve always HAD to use your real name by their terms of service. I have a fairly active Facebook and I only have *one* personal friend who doesn’t use their real name. Any other time I see someone using an obviously made-up name I find they’re invariably a troll or an idiot or both – and Facebook will chuck them off sooner or later.

          • Really,people have multiple Facebook accounts to play their online games,so they can trade stuff with themselves,all under fake names and they have been doing this for years,fake names,fake country of origin,fake birthdate,in fact to put all the correct details of your life on Facebook is folly.It makes it easy for anyone to find out almost everything about you?

          • Geyser, my wife had one of those secondary accounts once, for the exact reason you stated (right after Farmville took off) and Facebook locked her fake account. She had about 500 worldwide “friends” with whom she would trade and FB required her to correctly ID 15 random photos of her “friends” before they would unlock it. Needless to say, she never did get that account unlocked. LOL

          • Problem is that modern Admin tools pick up on a lot of things beside email, IP and other stuff.
            Once the Admins start poking around you are pretty much history regardless if you are on FB or on VC…
            It does not matter if the person calls themselves Joe Black or Fringebob McGooney.

            🙂

          • I use my real name on here, because I can’t see why anybody with any kind of ulterior motive would have any reason to abuse it. I have no expertise, and I’m unlikely to have anything controversial to say….. ignorant, possibly, from time to time.. but as I say, I claim no knowledge to rival MOST members hereabouts.
            Facebook as you rightly say, is a little different. On facebook I have my security set as tight as possible , and I try to keep all the important stuff fairly vague.
            Where I have a presence elsewhere on the net, such as when I was moderator on a tidal bore surfer’s forum, I used a pseudonym. Everyone in the UK scene knows who I am, and before too long that tag became my nickname in the water as well.
            It served me well enough. But by preference I like the straightforward honesty and personal responsibility which goes with acting in my own name.

      • TG is my initials and McCoy is my last name. Had a presence on a forum years ago that was used by another two T. or Tim McCoys. TG was simply
        a way of steering around that. So I kept it..
        I don’t Facebook or Twitter because of certain security
        issues I have had with a former significant other-who
        wouldn’t take no for an answer..

        • I had a lady show up on my doorstep on a Saturday several years ago demanding warranty service on her laptop because the manufacture had cheated and listed me as a depot level repair center, which I am not. Yes, I did warranty level work on their machines supporting a state contract but was not part of their company. Their website author took it upon themselves to list me as one of their offices to make their online presence look better.

          I was not a happy camper, nor was she, but I pointed her to a local place that could do the work… but I doubt that it was covered under her warranty.

          • This is weird-that woman who shall
            not be named-just pinged my LinkedIn connection.. I won’t
            respond, but my wife will not be happy.. Last time wife was on hand when she tried a velcro hug
            on me and went away with the feeling that her blonde scalp would’ve been flapping in the breeze on a high plains teepee.
            Due my wife, who is a bit more Native American than I…

          • My only bit of Choctaw ancestry caused half the family to try and kill off the other half about 150 years ago.

            Neither succeeded. Bonafide rednecks occasionally have trouble bringing a plan to fruition. Not that dissimilar to the Hatfield-McCoy thing, but they tended to keep the blood-lust inside the family.

    • I’m probably a slight bit younger than most on this blog. I’m not young, I’ll be 30 in less than a year, but for me, I grew up with the internet in large part. In the 90’s and all throughout the 2000’s, everything you did online as a youth was through a pseudonym, whether it was an AOL instant messenger account, your gmail account, myspace name, etc etc. So I think this just must be a difference in experience Mike, and also probably why you consider it slightly juvenile (because it is in a way).

      I have a great deal of respect for anonymity on the internet, and think it’s 100% necessary. But on the other hand, it also results in a LOT of trolling and vulgarity that terrible people think they can get away with when others can’t see who it is saying what they say. There are a lot of benefits to both. Losing anonymity generally results in greater initial credibility. For someone like you who in some ways works within this space, it’s probably not a bad thing to get one’s name out there.

      I on the other hand work for an advertising agency. When I mention to people in real life how fascinated I am by geology and volcanoes, I generally have to preface it, by “this is extremely random, but…” So for me, it generally works out better that I don’t attach my name to something like this, especially since my name probably shows up in search results for stuff more closely related to my real profession. Also, as lurking said, the more information about yourself you leave out there, the more easy you are as a target, not only for people looking to steal information, but for general trolls as well.

      • (in reply to you – but meant as a more general comment too)

        I’d refer you to this for an inkling of where I’m coming from – because I’m a hacker as well as a volcano guy:

        http://www.catb.org/esr/faqs/hacker-howto.html#style

        “The problem with screen names or handles deserves some amplification. Concealing your identity behind a handle is a juvenile and silly behavior characteristic of crackers, warez d00dz, and other lower life forms. Hackers don’t do this; they’re proud of what they do and want it associated with their real names. So if you have a handle, drop it. In the hacker culture it will only mark you as a loser.”

        Or in the science culture I might add 🙂

        • That’s just one guy’s opinion, and I don’t entirely agree with him. I’ve seen enough, even on here to prefer at least a shred of anonymity. And frankly speaking, I’m on here for my personal enjoyment and learning – there isn’t much I stand to gain by earning a reputation for blogging or commenting on volcanoes. If my discussion is useful to others, that’s great, but I’d prefer to let the discussion itself dictate that, not my name.

        • I second the “just one guy’s opinion” note.

          The only semi-real bit of that opinion are the ones that use 7337 speak in their names. They aren’t “leet,” they are just posuers. The same can be said for the 420 crowd in online games. And nothing really torques off a wannabe uuber sniper than knifing them in the back… or popping them with a rocket launcher as you go whizzing by in a buggy (PlanetSide2). In the BF1942 with DC mod game, while covering a street with a SAW and someone snuck up behind me, it was not uncommon for me to drop a grenade and jump out the window. Yeah, they flushed me from my position, but they have to deal with the grenade.

    • When the internet was young, it wasnt as needed or easy to get on it. So the underbelly of society was content on just yelling Nerd from offline when they found you were on it.

      Now there are scores of people on the internet with the social maturity of a bored teenager with a crayon with the powers of google and simple hacking skills at their fingertips. Piss off the wrong person and you will be send porn at work. Receiving Second Love advertisments on your family mail or get swatted. I learned my lession when someone started announcing grizzly murders on my home address over a simple polite political disagreement.

      Its also worth remembering that your (potential) boss will ready these messages too. And may get second thoughts if what they concidered to be a well educated employee makes the occasonal gaffle regarding a different topic. Or accasionally complains about work. Or notices that posttimes occur during working hours. On top of that. Chatting about visiting scary volcanos may rise some eyebrows with life insurances or unemployment agencies.

      Internet names also give in my opinion a better impression of who i am dealing with. A member called VEI6 with a seismograph avatar probably is someone that has a clear interest and education in volcanism. While HitlerRulez69 with a booty avatar is a obvious troll. Though to be fair, i have been proved wrong on that last argument occasionally. Latin names often can go both ways.

    • Why do I use a pseudonym on *here*: because it seemed to be the custom when I first started visiting the site regularly, and decided to create an account. Why do *I* use a pseudonym on here: because it adds a layer of privacy – though I know that doesn’t amount to much for those who really want to track my online identity.

      Having said that, there have been times when hiding behind a pseudonym has seemed unethical and I have added my name to my post. These include one occasion on here when things were a bit bumpy and someone who was at that time – though not now, I think – involved in running the site disclosed private matters without my consent.

    • I post under a pseudonym here but my pseudonym tells people where else they can find me, and there one can find my real name. So I’m not all that anonymous.

      To be honest I prefer my pseudonym to my real name. It’s a bit more descriptive of me and it’s fun! I use a variation of it most places on the web.

    • I am under my full name.
      But, as being a Swede I am uncomfortable with using the full name in daily dealings. Here you are more or less your first name. I do though sign the articles by full name when I remember to do so.

      I have though been on the Internet for about as long as you Mike, and I started out using a Pseudonym that I ditched later on.

    • I always use my name, and have never experienced adverse effects. It does make me more cirucumspect as to what I say. On many other fora anonymity seems to breed flaming /shouting etc and destroying the experience.
      Unhappily I have near namesake who is a real geologist: my middle initial is H, to avoid confusion. Perhaps I should have been ‘cobblers’.
      At least you all know your talking with a real person not a blue-whatsit. Although the day will come when a digital poster passes the Turing test. Or maybe s/he has already?

      • Sussed. Damn it!

        (PS, anyone who knows me will get me from my username: initials and DoB.)

    • I’m Clive – it’s my name. I don’t bother with a surname as since I used the Internet from around ’93 no-one ever seemed to use their full name. Then when more ‘Clives’ turned up I started using the psuedonyms like the others did. I never gave it much thought. But with Identity theft a growing problem I prefer now not to use my full name on any areas of the Internet.

    • In the UK, a pseudonym makes it safer to natter on the internet. Not from an authoritarian regime (yet) but from hackers and ID theft.

    • Came late to this discussion, sorry: but yes, this is my real name. No choice really, since I log in from Facebook, and as Mike (the other one) says, real names are a must on FB. I’m another poster who is just a volcanoholic, with no professional background (except a geology BSc)’

    • I use a pseudonym – but it is a spin on another of mine used in my photography, “LaconicPhotographs” or “LaconicPhotos.”

      I try to say a lot in single photos and I typically talk in “bullet format” – hence “Laconic.”

      On here, it is difficult to be succinct as my discussions tend to be questions – hence the “Verbosely.”

      AND, the interwebs invariably misinterpret “succinct” as “curt” or “short.”

      If I type like I talk, I may as well type in ALL-CAPS; similar reactions.

      I don’t mind if I am known as “Greg Roane” instead. Easier though, to not mispronounce “VerboselyLaconic” than it is correctly pronounce “Roane”, in my experience.

      It is up to y’all.

  8. One quick note – I don’t think Aniakchak is the largest volcano in Alaska. At the very least, there are a lot of other volcanoes that can make arguments for being bigger, and there are at least 3-4 with larger calderas. Don’t mean to nitpick, the article was well written and all.

    • I was also pondering this, but AVO and GVP gives it as that.
      I think they put in that moniker due to several factors, it has a very large fotprint and the caldera is among the largest. I think the correct term would be “Alaskas Largest Volcano when you Factor in a Lot of Factors”, but the title of ALVFLF is a cumbersome title even for a VEI-7 volcano 🙂

  9. A little off-topic here, but GNS Science / Geonet NZ shared Civil Defence ‘s graphic interpretation of the current state of NZ’s volcanoes on facebook:

  10. The “swarm” that looks like it’s associated with the M3.3 at Bárðarbunga in the wee small hours today interests me: the quakes take place within 20 mins of each other but they are fairly widely dispersed (as swarms go) and the depths vary quite a lot.

    Tuesday
    05.04.2016 02:46:28 64.671 -17.515 0.4 km 1.2 99.0 — 3.4 km N of Bárðarbunga
    Tuesday
    05.04.2016 02:42:10 64.638 -17.512 3.9 km 0.7 99.0 — 0.8 km ESE of Bárðarbunga
    Tuesday
    05.04.2016 02:33:03 64.660 -17.541 11.3 km 1.2 99.0 — 2.3 km NNW of Bárðarbunga
    Tuesday
    05.04.2016 02:32:47 64.705 -17.571 10.6 km 1.7 99.0 — 7.5 km NNW of Bárðarbunga
    Tuesday
    05.04.2016 02:30:38 64.639 -17.506 2.5 km 1.2 99.0 — 1.0 km E of Bárðarbunga
    Tuesday
    05.04.2016 02:28:39 64.632 -17.516 3.5 km 0.7 99.0 — 1.1 km SSE of Bárðarbunga
    Tuesday
    05.04.2016 02:25:45 64.668 -17.503 0.1 km 3.3 99.0 — 3.3 km NNE of Bárðarbunga

    Is it likely that the ‘quakes are causally related to each other, and if so, why might they vary so much in depth and location? Cheers.

      • It is blocking in the caldera, the same as happened in Askja after 1875 but we can’t see the progression.

        • Ah, OK, thanks.

          I wondered about blocking. What I hadn’t appreciated was that when blocking is going on eqs could be in a widely dispersed “swarm” like this. So presumably when blocking is happening there can be a causal relationship between a M3.3 at 0.1 km and a M0.7 2kms away, 3 mins later, etc. If there can’t be a causal relationship, then the occurrence of all those eqs in such brief period of time would seem statistically unlikely to my non-scientific mind.

          Thanks again. Slowly, gradually, we learn 🙂

          • It is also worth to keep in mind that smaller earthquakes are harder to locate, so the error source is so big for an M0.7 that it can be kilometers off.
            That is why I always try to filter off all earthquakes smaller than M1.

  11. … and just to rub it in… the sun is glorious today. Nary a cloud in the sky.

    I’m not a great fan of intense sun, but it’s bright enough to be impressive to me. Deep blue sky and blazing sun. .. and only about 72 F outside.

  12. Its also worth remembering that WordPress accounts are used for all sorts of sites and comment sections. Not just this one. Even though I trust this site. I still have to take into account the others.

    • Sorry about this. This post was meant as a reply to the nickname discussion above. But WordPress and my browser screwed up.

    • Not a prob. If you like, I can try to shoe-horn it into the sequence.

      Edit Add: Never mind. If I do, it might break something.

    • Looks like someone dropped it, kicked it, rolled it down the hill, batted it back up, and threw it back in its hole.

    • The other recorder shows something at the same time but much less intense. No idea what it could be.

      • It looks like it was not operating properly and someone showed up to do a repair and now it’s working?Or it was the bear…

  13. I have noticed this small spot about 20 km NW of Askja that has seen a small swarm of quakes

    Within the red circle on the picture which is about 2km across there has been 20 recorded quakes (in the last 5 weeks), most very small the largest at M2.4, one today at M2.1 most from the surface down to about 3.5km deep.

    Did search for anything regarding this spot but have found nothing at all, looks like it could maybe be an old fissure eruption site. Listed as Lokatindur on IMO quake list.

    Is this most likely hydrothermal, thoughts anyone?

    • Ian, I agree, the activity in this area has been interesting.

      A small point, but I think Lokatindur is the small, light brown hill to the right of the bottom-ish right line on your circle. This page should show it fairly clearly, always assuming the labelling is correct, which it isn’t always:

      http://vegasja.vegagerdin.is/eng/

      “Tindur” means (iirc) “pointed peak” in Icelandic and on your image the shade at the NW edge of “my” hill suggests a fairly pointed peak. Also, from the colour of the hill it could be hyaloclastite, which would produce a “tindur” shape when eroded.

      released from the clutches of akismet /Hobbes

      • Thanks AM, added that map to my bookmarks.

        You are correct that is the right position for Lokatindur and I just ballparked the quake swarm location.

        I have gone back to fix the location better and the quake swarm location is actually just a little to the northwest of the circle I drew, it should be centered on the end of what appears to be a ridge, the M2.1 quake today was 6km WNW of Lokatindur

        • I would have linked to this website but the key section (in Layers) is down for me at the moment: http://futurevolc.vedur.is/

          Interestingly enough, if I’m correct as to where Lokatindur is, it’s right on the edge of the Askja fissure swarm.

          • am57 – According to futurevolc it’s right on the edge of the Bardy fissure swarm.

          • Thanks for putting that together, BG. V interesting.

            It looks like Lokatindur itself is also right on the edge of the Fremrinámar swarm.

        • Aargh! Apologies Ian F: I misread your original post. You are quite correct about the location of the swarm itself. Thanks for your patience. I’m a humanities academic – strange how one can be very careful about detail in some fields but in others the same carefulness eludes one. ‘Twas ever thus for me, even at school my science work was littered with careless mistakes.

          Beardy Gaz: Yes, you’re right; my mistake, as above. It’s a pity that futurevolc won’t show different volcanic systems’ fissure swarms simultaneously. The eq swarm we’ve been talking about is just outside Askja’s. Perhaps the unrest in Askja is affecting this part of the Bb system.

          Is futurevolc working properly for you?

          • I agree, adding multiple volcanic features would be a nice feature. Maybe they’ll bring it in post beta. The overview map is rather small with all the ‘basic’ swarms interlaced.

            It’s probably stress changes between the two systems from the historic and current deep activity. The fissure swarms do overlap in a few places, but I’m sure it’s not as simplistic underground as the drawn 2D fissure swarms show.

            It’s working ok in Chrome for me this morning, although it errors when adding the earthquake layer.

          • That location rings a definite bell. I’m *sure* I remember looking at activity in that area 4 or 5 years ago – even to the point of checking out Google satellite views of the topography and earlier lava fields.

          • Not a problem AM, I was being a little sloppy myself by not putting it in the exact location. I am a moldmaker by trade and precision is something we are a little anal about…. usually.

            Looking further down the page at the graphic Rob posted I see two things.

            First, there seems to be a line of quakes since that looks like the shape of a fissure.

            Second, the graphics of the fissure swarm in that picture put these quakes in No-Mans Land and have the latest BB eruption in Askja’s swarm field. The graphic furthest above the one Beardy posted first, has this area in the BB field and then, the overview graphic Beardy just posted, has the BB field overlapping the Askja field.

            So it seems there is still some adjusting and rethinking going on somewhere

            Mike, when searching for info on this spot, google brought up posts from this VC in 2013 & 2014, your memory does not fail you!

            From past posting here at VC

            Sunday
            03.03.2013 23:41:14 65.183 -17.020 6.7 km 3.0 99.0 8.8 km WNW of Lokatindur
            Sunday
            03.03.2013 23:36:55 65.181 -17.012 0.3 km 1.9 99.0 8.4 km WNW of Lokatindur
            Thursday
            28.08.2014 17:53:20 65.182 -17.055 6.3 km 2.8 99.0 10.2 km WNW of Lokatindur

          • Ian – they definitely overlap where the Holuhraun 2 eruption occurred as in this merged image I created.

    • Kind Admin Person:

      I have tried to post a reply to Ian F, but it contained a link to an Icelandic website so perhaps it’s got stuck in the dungeon. If it has, please would you release it and delete this. Many thanks.

    • Lokatindur is an eruption site belonging to Askja. It is sitting on a radial fissure from Askja, something that Askja is quite special with. It has several of these radial fissures.

  14. And here we said goodbye to Geyser.
    The promised bin number 3 is awarded, and as promised also a permban.
    Total tally…
    16 warnings.
    3 one week bans.
    2 permanent bans (this time it is for good without possibility for parole.
    /Admin

  15. Another batch of deeper quakes at Askja. This time again at a new location. Interesting.

    • Another deep batch – that’s the interesting thing. Askja has had a lot of deep quakes in the last few months.

      • Yes, and the locations vary, unlike at Katla for example. Bigger number of potential “dikes”?

        The last deep batch was E of Askja and S of Herdubreid. I have the image still stored somewhere.

        • This last batch is at the same location as the one a few hours earlier and has a similar, but more defined signal.

    • Askja as a volcanic system has always had very varied locations for it’s eruptions so it is in the line of what we could expect prior to an eruption.
      Currently it seems like Askja is moving towards an eruption, only problem is that we do not know when (if) it will happen. It could be in 2 weeks or in 2 decades. Personal GUESS is that it would be at anything from 3 months to a year.
      The reason behind my line of thinking is that the current activity at Askja with deep seismicity is now showing more deep earthquakes than what we saw prior to the Bárdarbunga hubbub.

      A reminder, the activity at Herdubreid is not related to Askja. That is from an initial intrusion that over several years have been migrating from Upptyppingar to Herdubreid and that has had a couple of refills from depth. Another set of system altogether.

      • If my memory serves me correctly, wasn’t there a historical Holuhraun eruption in the 1700’s that was originally attributed to Askja before current events made people realize it was likely a product of Bardarbunga?

        If so, this could be an interesting repeat of geological events if we were to have Holuhraun episodes that preceded an Askja eruption.

        Of course, I would have to imagine that previous Holuhraun area events could have just as well originated from the Askja central volcano, and that’s still probably the more likely central source for this stuff.

  16. Looking at the Aniakchak webicorder, still seeing a lot of clipping earthquakes. I can’t imagine those are aftershocks at this point, at least not the ones showing up there. Not saying anything is going to develop there, but interesting to watch at least.

    • I have no idea what to get from this but here is a more detailed look at the quake waveform from two stations ANNW and ANPB. You can see the quake on the drumplot, it is the last one to occur for size comparison

  17. Interesting 2+ quake under Lake Amadore Near Chester, Ca.
    The area has some very interesting volcanics and tectonic
    features. It sits at the south end of the Cascade Range and
    north end of the Sierras ..

    Tried to fix that one, but could not find the original image.
    /Admin

  18. And now for something completely different…

    Chimborazo is the highest mountain on earth if you count from the center of the planet. Or in other words, Chimborazo is the peak of the Globe, but not the highest point measured from sea level.
    This means that this active volcano has surpassed Mount Everest according to French geodesicists who confirmed this during the third geodetic expedition.
    Last eruption was in 550AD and it is likely that the volcano will continue to grow and further outdistance it’s Himalayan opposition.

    You will never unlearn this. 😉

      • Tallest here is referencing quite literally, the highest point on earth, not necessarily the highest prominence, or greatest distance from base to top.

        Everest is still significantly “taller” than Chimborazo, but the area closest to the equator bulges out a bit due to the earth’s rotation, making it further from the earth’s core by comparison.

    • Don’t think so, more likely to be one of those weird non-double couple mechanism earthquakes. But, we will have to wait for the data.

        • So far it is quit. But getting a swarm at that depth NE-corner of the caldera is interesting. If this does not shake something loose I think we can say that nothing will for the moment due to the pressure being to low.

  19. Three eqs of greater than M6.7 in four days. Depths 24 – 35 km. Seems more than tectonics/ aftershocks.

    • Vanuatu often has those doubles or triples. The fault is discretely blocked into segments there, so if one goes often another takes off in a day or two. It happens every few years.

  20. From the IMO.
    Today (8. April) at 00:10 an earthquake of magnitude 4.2 occurred on the northern caldera rim of Bárðarbunga. It was the strongest earthquake measured in the area since the end of the eruption in February 2015. Around 15 aftershocks were detected so far, the strongest was magnitude 3.5 at 01:01. No signs of magma movements or volcanic activity are observed. IMO is closely following the situation 24/7.

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