Special report: Pre-earthquakes to the Mw8.9 earthquake in Japan

It appears that before the large earthquake that did happen today (11th March 2011) there was a sequence of a pre-earthquakes. The pre-earthquake to the large Mw8.9 earthquake was a Mw7.2 (EMSC data) that took place on the 9th March 2011 at 02:45 UTC. This pre-earthquake was followed by about dozen or so aftershocks, the largest one being Mb6.2 (EMSC data).

The problem with this type of pre-earthquakes is that you cannot know that they are pre-earthquakes until after the large earthquake takes place. Because of that fact, it is only now known that the Mw7.2 was a pre-earthquake to the Mw8.9 earthquake that did hit Japan today (11th March 2011).

Please see BBC News or CNN for more news about this earthquake.

For webicorders that show the earthquake can be found here. USGS webicorders can be found here.

85 Replies to “Special report: Pre-earthquakes to the Mw8.9 earthquake in Japan”

  1. The typical statements I read/hear from USGS or CalTech seismologists re: pre-quakes, is the 5%+ increased risk of a larger quake following the pre-quake. I guess this was the 1 out of the 20.

    Sooner or later, this will happen to So Calif only this time it will be in the center of an area with endless cities and high density where the entire infrastructure is within and circled by the “kill zone” of the quake, including major railway, transportation, electrical, NG, oil and water corridors, 2 major ports with poor soils all which service the SW U.S., a nuclear power plant and milions of densly packed people. Not to the mention that Calif is 12% of the U.S. economy and is deeply overwhelmed in debt.

    The estimated death toll ranges from 5-10,000 with over 200 billion in damage should the San Andreas have a major quake which is estimated to be in the neighborhood of high 7’s to 8+ with 2-3 minutes of shaking. The entire So Calif area is a web of complex faults in which it is likely that these other faults would rupture as well. THIS, is why I moved from So. Calif.

    1. Oh, did I mention that the southern portion of the San Andreas Fault (SAF) which terminates in near the bottom of So. Calif, is considered to be statistically 150 years overdue and has stored up to 33+ feet of tectonic movement where some seismologists are now saying there is a 99% chance of a major rupture (150+ miles ) in the next 30 years. The SAF and its sister faults run right along the most dense portions of So Calif from the south to the north putting all those people in the “kill zone”. Ok, back to my hamburger.

      Oh, quick question, why would anyone want to live in Bombay Beach?…or Palm Springs for that matter, unless you have a deep faith.

  2. Well… one thing that SoCal has going for it is that it is not a subduction zone.

    No subduction zone, no “megathrust” fault configuration. Bandar Ace – Megathrust. Japan – Megathrust. Cascadia Subduction Zone – Megathrust. (see where this is going?)

    On the other hand, SoCal does have a locked wrench fault… and those aren’t pretty when they let go.

    1. The consensus seems to be 8.0 for an estimate of the largest possible quake. Its the very poor soils throught the red shake zones in the affected along with the high population density that makes the damage scenarios relatively high even with the strict building codes. The other factor is the myriad of faults that would be affected.

  3. Wait! What?

    “Fukushima Prefecture says 3 patients at a hospital near the damaged nuclear power plant have been exposed to radiation.

    The 3 were chosen randomly for radiation testing from 90 patients and staff who were waiting for airlift by helicopter at a nearby high school on Saturday afternoon.

    The prefectural government says the 3 need decontamination to remove the radioactivity. They have not shown any reaction or physical symptoms of the radioactivity yet.”

    Err… what about the other 87? Did anybody go back and check them?

    1. There is a several thousand fold difference between te amount of radioactivity to declare a person contaminated before any symptoms of radiation illness happens. The radionuclides are short lived ones, so it is probably only of academic interest whether others are slightly contaminated and they won’t be contaminated for long enough for it to matter.

      1. That depends on the contaminating nuklids. If it is for example Caesium 137, then you face a nuklid with a half life of 30,12 years, which can be easily incorporated into your body. There have been reports about caesium contaminations.

  4. Saturday
    12.03.2011 18:56:56 64.505 -17.512 1.1 km 3.1 90.1 14.4 km E of Hamarinn
    Whilst one is looking the other way.

    Good luck Japan

    1. Dunno if I would sweat that. That transform fault zone goes off from time to time. I remember it acting up about 5 years ago and I was certain something was up. Natch, I was wrong.

      “The basalt basement of the Oregon and Washington Coast Ranges is an accreted oceanic terrane sutured to North America in Eocene time. Also known as Siletzia, it consists of Paleocene to early Eocene submarine and subaerial tholeiitic and alkalic basalt thrust beneath the continental margin. Siletzia is 19 km thick on the Olympic Peninsula and may exceed 30 km in Oregon based on seismic studies.”
      WELLS, Ray E., U.S. Geological Survey; http://gsa.confex.com/gsa/2007CD/finalprogram/abstract_121123.htm )

      Rotting around in the search engines for other studies on this chunk-o-crust seem to point to it being a relic of the Farallon, sliced off by the Yellowstone hotspot, stripped of it’s basaltic material, and left dangling in a near vertical buoyant state in front of the submerging front of the Juan de Fuca (and friends)

      Why is this significant? Well, we know from geological studies of the Cascadia SZ that it’s eerily quiet. At least when compared to other ‘megathrust’ locations (Sunda trench, Japan trench, Java trench etc.) In fact, the last … sort of historical record of it doing anything significant was when it caused the “silent tsunami” in Japanese historical records.

      So… why so quiet?

      My read is that not only has the the main pulling force of the Farallon been taken away after it detached (thank you Yellowstone hotspot), that the Siletzia fragment is somewhat blocking the Juan de Fucas path.

      Sort of a seismic speed bump.

      Note/Caveat etc. : I am not a Geologist. I am not Michio (Cliff Claven) Kaku, and I don’t fly a spaceship.

    2. Did you see the footage of the 60+ foot wailing vessel trying to bow into the first wave of the tsunami? almost breaching? I held my breath. Reminded me of Tom Hanks in Cast Away trying to make the first wave…hehe.

      I used to sail Aquarius and La Paz in NASA (North American Sailing Assoc) a long time ago and did some ocean racing for several years…Newport to Ensenada regatta, Santa Cruz Islands, etc. I’ve lost my sea legs now…pity. Miss the heck out of sailing and can’t afford a hole in the ocean now..so.

      1. We still sail, did transatlantics in 2005/2006–visited volcanos -Azores, Canarys Islands, Cape Verde, Caribbean – Monserrat, St. Vincent, Jumping Jenny (underwater), St. Lucia, Martinque..have rock samples from each. Got us started on volcano observing.

  5. Diversion of sorts….

    The Mag 3.1 ranks as 1,876 Cheeseburgers or 4,491 Twinkies in energy.

  6. This is not the first time my sense of humor has gotten me in trouble…sorry I’ll save those for the bar.

    1. Sorry if my extension of the cheeseburger analogy cause you to mispost. The twinky idea came about from the Ghostbusters Scene where ‘Dr. Egon Spengler’ is talking about the energy of a 35 foot twinkie.

      As for the “wave”, that cluster falls in line with the trek up from the Rivera plate’s triple junction. Just remember that the “wave” idea is not proven. It’s just a thought. A sort of mental exercise. The key to seeing if there is anything there, or if it’s a repeat, is to remember this one and look for another event to occur about a 140 miles North. (roughly) in a month or so.

      I can’t remember if there was a batch further south at the triple junction kicking this off… I think there was, but I’m not gonna lay any claims to it. There are enough Loons jumping around now and I sure don’t want to join them in pissing people off.

      1. Nice read.

        And logic.. or the void of logic, races on.

        In order for this to be valid… at least to my line of thinking, is for the distant quake events to lessen the compressive strain locking the other side of the plate in place. That or it changes the angles of that locking pressure, possibly re-orienting where the “burrs” on the faults lock together.

        Again.. I am no geologist, and I tend to believe in migrating stress waves so I am a bit biased in that regard.

      2. The stress wave (to borrow an idea) in Japan is moving towards south towards Tokyo as the plates adjusts to the new reality formed by the 8.9 and stressors migrate along the fault. I don’t recall the percentage for aftershocks 1 magnitude under the main shock, but if I were in Tokyo, I would be very concerned. This whole area is very unstable now. I’m sure they are RACING the clock to stabalize these reactors.

      3. I’m still having issues with the location and orientation of this quake. It was very shallow, and back on the mid section of the accretion lens… at lest as far as I can tell. I world have thought that a megathrust would be more towards the toe. This was almost like it snapped that wedge in two.

        Historically, they had a really nasty one in the Tokyo area. I saw a paper the did some re-evaluation of it’s parameters… and the conclusion was that it was definitely less that 10 km deep. I plotted out the residuals from that paper, and to my untrained eye, it looked to be about 1.2 kn deep.

      4. And a correction… It was near the toe. After pulling good bottom data off of the Google Elevation API it maps out right where it should have been.

  7. These Gulf of Mexico quakes are tallying up. 8 or 9 now all in the 4’s, 5’s. Whats going on down there and is it related to the 8.9. Rhetocial questions from an arm chair idiot. Scratch that… I’m a qualified Geologist.

    Where’s Professor Lidenbrock when you need him.

  8. The tremors of the VAT station, my attention that 2-4 Hz is barely moving during storms, the frequencies of 0.5 to 2 Hz if they have their ups and downs, this behavior a long time that I watch, when you have a change is sharp in 2-4 Hz
    Translated by Google.

  9. I just heard that vulcano Shinmoedake in South Japan erupted. Can anyone confirm this?

    1. If there was a eruption in it. That would not be connected to the Mw9.0 earthquake in Japan. As that volcano is in far south Japan, far away from the Mw9.0 earthquake. I am more concerned about the nearby volcanoes closest to the main earthquake.

      This volcano also erupt frequently. With last eruption starting on January 19th, 2011.


      1. Sure this isn’t Kirishima? It’s part of the same complex and it’s really just a matter of what the individual holes are names.

      2. Yup… and if I remember correctly, Sakurajima started up a bit after Kirishima.

  10. I just come back from a weekend out. This was a huge disaster, earthquake, tsunami and nuclear worries, it’s so sad for the people in Japan.
    My blessings to them.

    This is also a show of how nuclear energy has its rare yet big risks.
    A Chernobil-like disaster would be catastrophic close to Tokio.

    1. You can’t get a chernobyl like disaster because the control rods are already in to core. The only meltng possible is from residual heat which there is no ccolent to cool. The core could melt and distort, but what happened at Chernobyl is not possible with so much neutron absorbers (control rods) in the core.

  11. Good evening Jón and everyone.
    Trying to cope with all the frantic news from Japan.
    There is this stunning timelapse of Shinmoedake (Kirishima) volcano on Japan’s Kyushu island. The same eruption that we’ve been watching over EB. Don’t know if it has been posted before. (Thanks to Shérine)
    Both Sakurajima and Kirishima have shown intense activity before the quake, so I wouldn’t jump to conclusions so far.
    On Caesium 137.
    There was this ugly accident here in Brazil which involved a whole family. (Paragraph grabbed from Wikipedia):
    “The improper handling of caesium-137 gamma ray sources can lead to release of this radio-isotope and radiation injuries. Perhaps the best-known case is the Goiânia accident, in which an improperly-disposed-of radiation therapy system from an abandoned clinic in the city of Goiânia, Brazil, was scavenged from a junkyard, and the glowing caesium salt sold to curious, uneducated buyers. This led to multiple serious injuries from radiation exposure.”
    I remember that a kid found it so beautiful the “metal blue powder” and took the piece of radioactive metal with him. Terrible stuff.

    1. I don’t quite remember, but I think two people were killed in this family.

      1. Found this in another entry in Wikipedia:
        “The Goiânia accident was a radioactive contamination accident that occurred on September 13, 1987, at Goiânia, in the Brazilian State of Goiás. Considered one of the worst nuclear disasters in history,[1] it took place after an old nuclear medicine source was scavenged from an abandoned hospital site in the city. It was subsequently handled by many people, resulting in four deaths and radioactive contamination of 245 other people.[2] The dispersal of radiation was equivalent to a medium-size dirty bomb.”

      1. Indeed, no comparison.
        Just posted because you mentioned and it was still fresh in my memory.
        I’m very concerned about Japan, and all my sympathy goes to this brave, resilient, people who have gone through all sort of natural disasters, not to mention the man made ones.
        BTW: Don’t you think that the aftershocks are now slowly moving southwards, or it is just a wrong impression?

      2. Yes, it is.

        But it seems to be… key word SEEMS to be moving south.

        Its gonna take a bit more watching to say for sure.

        Note; capcha on a phone blows goats.

      3. I agree.

        BTW there just seems to have been a 6 near Nagano on the West coast.

      4. And as a histogram.

        Definitely favoring the southern area.


        The big FREAK-EX that people are jumping on, is will this be a repeat of the 1854-55 Great Ansei quakes… or the 1923 Great Kantō event.

        Two of those were pretty much right in Tokyo’s backyard.


        (Terminology note: FREAK-EX, a variation of FLAIL-EX… typically a Naval warfare exercise or operation that goes horribly wrong due to incompetence, overconfidence, or general ineptitude of it’s participants. Applies equally well to normal day to day operations. The Freakex variation is pretty much the same, but done mentally as people ruminate over what could happen should theoretical certain circumstances come to pass)

      5. The grammatical dyslexia is free.

        Should have read “certain theoretical”

      6. As an engineer I am concerned if they cool the uranium core directly with sea water, because salt will accumulate on the hottest parts and work as an insulation and can be ineffective as coolant after some time.
        Also the excessive coolant have to be drained to the environment.

      7. Saltwater has being used for emergency coolant before and will work if the temperature is below 45°C , but if it is higher, salt will accumulate on hot surfaces and insulate the surface from the water, and the hot parts will be dry and covered with salt and overheat.
        Corrosion comes later and will damage surfaces of most metals except gold , titanium and high quality stainless steel.

      8. Sea water has been used as a coolant before? I haven’t read about this. And this is only the very last measure, before nothing is possible any more. The technicians at Fukushima must be really desperate.

  12. Hope the best for Japanese people in this terrible disaster.
    I lit a candle for the spirit of the japan folk.

    1. Well, I’m not trying to whizz in anybodies wheaties… but hey, I could really care less.

      First of all, I have yet to see a really nicely packaged definition of foreshock. Everything I’ve seen indicates that you don’t know it’s a foreshock until after the mainshock has made itself know.

      Aftershocks, the way I understand it, are the local and surrounding faults adjusting to the strain relief of the mainshock and the terrain adjusts to accommodate that added load. In some cases, the extent of the aftershocks can give you a clue as to the size of the slip area and allow you to get a better calculation from the magnitude moment.

      So… a Mag 7.2 goes off in the VERY SAME ACCRETIONARY LENS, dumps about 3,981.07 petajoules of energy on the surrounding structures/faults, a Mag 8.9 follows along 42 kilometers away, 50 hours later, and some Michio Kaku wannabe at Harvard has the temerity to come out and hint that they are not related because they weren’t on the same fault plane?

      Um, “yeah, riiiiight”

    2. It appears to me as the 7.2 earthquake did relive stress on eastern part of the subduction zone, and therefore putting more stress on western part of the zone and that tripped with 9.0 quake.

  13. Hi,
    I found a very interesting statement of an expert who tries to analyze and explain the observations at the Fukushima power plant. It is a rather long, but very good article. Moreover, it provides a very good insight in the operation and safety measures of this type of Nuclear power plant. Still a dangerous event but probably not as devastating as it seems.

  14. Well, that did remind me.. I have a nice profile of the area using all quakes back to 1973 as a reference to see the shape of the down going plate. The recent 8.9, the “nin foreshock” 7.2, and a 7.1 on the other side of the trench are labeled with their order of occurrence.


    1. Very nice plot. I see that the earthquakes on the pacific plate side line up nicely at about 35km. I wonder if this is the plate/mantle boundry?

      1. Well, part of it has to do with the paucity of seismic gear in the area. Oceanic quakes almost never gear up close where you can get those really detailed waveforms. Failing that, they have to interpret them as they can get them and do phase picks and analysis on that.

        From Routine Data Processing in Earthquake Seismology discussing the layout of the JB tables (predicts arrival times vs distance from quake)

        “Hypocentral depth is given as a fraction a of earth radius minus the crust (6370-33)a+ 33, so the depths 0.0, 0.01, 0.02 etc correspond to 33, 96, 160, 223, 286 and 350 km respectively”

        So… 33 km would be one of those depth ranges that quakes fall into if the highly detailed waveforms are not available.

        I usually attribute an artifact such as all the quakes lining up at one depth to instrument errors. In Iceland, despite the phenomenal quality of their products, tend to have quakes showing up at 5km depth.

        The way to read it is that yeah, they are around that level, but it’s not exact. There is ample room for error above and below that level.

        Oh, another thing. This end of the Pacific plate is the oldest. Being older, it’s cooler, and thicker.

  15. Interesting 5.1 aftershock on the fault boundary right off the coast of Tokyo that resulted in a tsumai watch. I am concerned this might be the area for any large aftershock around 1 magnitude under 9.0 as the the aftershock pattern has been migrating south. A large quake in this area of the fault would be devastating to Japan.

    There is an outpouring of international generosity again which is always very heart warming to see. Our brothers in Japan are in great pain.


    1. the weather has been bad here in iceland since yesterday evening. So that must play some part in the frequency band.

      1. but as far as i understand it, the low frequency shouldn’t be affected that much by weather. it might be the case but i remain sceptical.

  16. The Shinmoedake Volcano in Japan erupts just as aftershocks from the 9.0 quake begin to subside.


    “Officials are not yet certain whether the eruption was a result of the massive earthquake that rocked northern Japan on Friday. ”

    http://is.gd/mJioQz <== Moon check. Nope, not that.

    "Sunday's eruption, which was the biggest volcanic activity in Shinmoedake in 52 years, caused widespread destruction and panic. The blast could be heard for miles, and shattered windows four miles away, the BBC reported. Hundreds of people fled the area as the volcano spewed debris, including hot ash and rocks, more than 6,000 feet in the air, according to BBC reports."

    Space Weather and EQ 9.0 and Volcano:

    1. Shinmoedake volcano in the Kirishima volcanic field started explosive eruptive activity on Jan 11 this year. After the initial explosive phase, it started growing a lava dome, which is shattered by explosions from time to time, and they are likely to repeat for time unknown.

      The latest explosion _might_ be triggered by the EQ, but the volcano has been quite capable of producing explosions on its own.

      1. Thanks. If I were not sleep deprived, I might have figured that out. LOL

  17. I just watched a tv program about Icelandic volcanoes. I’m not sure it can be watched from other countries than Sweden, but I would suggest you give it a try. It was filmed after the Eyja eruption and among other things they descend into an old magma chamber, it was very interesting. The speaker voice is in Swedish, but all interviews with scientists etc. are in English and the landscape is beautiful.

    1. I’m in the US and am able to hit it… almost unwatchable from the latency and buffer load times. Giving a shot at pulling down the raw link. That might work.

      It looks fascinating.

      1. I’m in the Boston area, and it loads fast and plays seamlessly with no pauses … very HQ video … using Verizon fiber optic connection.

        Here’s the description in English:

        Part 7 of 18: The volcano deep
        A year ago, hit the ash cloud from Eyjafjallajökull throughout Europe. Now follow our film crew, scientists down in the still smoldering crater and underneath the glacier where the ice is still melting. Scientists seeking answers to the question of which volcano which is currently on tour and what controls magma movements in the rock. For the first time ever you go deep down into an extinct volcano empty magma chamber and exploring the volcano’s interior. Programme Manager, Victoria Dyring.

        Some of the narration is in English, fortunately.

        Thanks for the link. Yes, it is very interesting!

Comments are closed.