Special report: A Magnitude Mw8.9 earthquake struck Japan

At 05:46 UTC (14:46 local time) there was a Mw8.9 (or up to Mw9.1, it is hard to terminate the exact size of this large earthquakes right away) earthquake in Japan. The depth of this earthquake was registered 24 km depth. But that is the reason why this earthquake did create this big tsunami. According to news there has been great damage following this earthquake. Loss of human lives following this earthquakes is also feared. But already there have been found bodies of 300 people that died following this earthquake. After the earthquake a huge whirlpool was created according to BBC News, a video of it can be seen here.

The rupture zone is estimated to be about 500 km (EMSC). But that number might change on a later date. A lot of aftershocks have followed the main earthquake. The largest aftershock did reach Mw7.0 in size so far. But there have also been a lot of earthquakes that have magnitude Mb6.0 – Mb6.9. Many more aftershocks of size Mb5.0 – Mb5.9 have also happened. I have no information about smaller aftershocks. But I am going assume that the number of earthquakes in smaller range is in the number tens of thousands.

This earthquake was recored on all my geophones. Even the one that I have here in Denmark on the second floor where I live.

Above: The Mw8.9 earthquake in Japan on Heklubyggð (Iceland) geophone. This picture is under CC licence.

Above: The Mw8.9 earthquake in Japan on Hvammstangi (Iceland) geophone. This picture is under CC licence.

Above: The Mw8.9 earthquake in Japan on Sønderborg (Denmark) geophone. This picture is under CC licence.

I am going to post more information about this earthquake when I have them. I am also going to post more information about the aftershocks later on.

Please check all major news networks for news about this earthquake.

19 Replies to “Special report: A Magnitude Mw8.9 earthquake struck Japan”

    1. No, many aftershocks are pretty normal. The largest usually are one order of magnitude weaker on the earthquake measurement scale. Since this can still be 7.something, there will be more shaking going on.

    2. I’ve been meaning to make a power decay plot of an aftershock set to get a handle on the rate of decay for later reference… I have just never gotten around to it. As noted, the aftershocks are pretty normal… and as a rule, the bigger the main shock the more aftershocks you will get.

      If you dig back a month or so, you can take a look at the aftershocks for the Bonin Islands group and see the same thing… just smaller.

  1. Does anyone have any idea what level of energy was released during this big one + additional aftershakes?
    Is this kind of major earthquake in any way comparable to major eruption (VEI 5-6?) in released energy?

    Just thinking of the mightiness of Mother Nature.

    1. I tallied up the main shock at about 22,500 megatons equiv TNT,

      I haven’t summed up the rest, bit it’s nasty.

    2. 1.425E+18 Joules or about 22,587.8 megatons TNT for all quakes total.. from the 7.2 pre-shock until now.

  2. 6.6 magnitude in central Japan. Not aftershock. What happening earth right now?

    1. Large earthquakes like this one activity nearby faults if they have the energy to create earthquakes.

      This is what happened when two Mb6.3 (18:59 UTC) and Mb6.1 (19:02 UTC) did happen in Japan. This is going to continue to happen in Japan for coming weeks and next several months.

      1. There is growing research and evidence that supports the theory that large quakes can trigger or be the causal factor in quakes on adjacent faults as stress is transferred. In fact, one leading study done in Japan has what is called the “dohnut” theory in which quakes occur along adjacent smaller faults in a wide circular pattern that narrows until they trigger a major quake on the larger fault near the center of the dohnut. It would be interesting to see a time/distance map of quakes on faults adjacent to the fault that had the 8.9 and try to find a reliable dohnut…which of course could have chocolate sprinkles.

  3. As another layman I am staggered that your geophone in Denmark is that sensitive, I’m truly amazed. Fantastic! :O)

    1. I apologise profusely for my badly worded post. I do of course have utmost sympathy for all of the terrible consequences of this disaster

  4. Safety zone around Fukushima just widened from 10 to 20 Km’s.road rivsk

  5. Concerning big quakes creating other quakes:

    3 days before the earthquake in Indonesia in 2004, there was a very big one, something like 8.0 in the north border of Antarctica plate, where the junction runs to Australia and Indonesia. Even if it was that far, some geologists have wondered whether that was a precursor to the 9.2 indonesia quake, the energy of which travelled across the southwestern Pacific ring of fire. Maybe it was just a coincidence.

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