Preliminary Data on the Tohoku Earthquake

Harvard Seismology has put together a fascinating set of maps and preliminary data about the Japan earthquake. All of it is interesting, but two especially struck me in relation to the events at Fukushima Daiichi.

Here’s the explanation of this map:

The figure … shows the relative amount of energy release from various locations that radiated energy during the first 25 minutes (darker orange showing higher energy release). The largest energy release occurs downdip of the epicentre, and the regions south of the epicentre release more energy than segments to the north (partially due to multiple large aftershocks on Mw 9.0 earthquake).

If I read this right, the Onahama and Fukushima plants were struck by the bottom most energy release, but the text indicates Fukushima would also have been affected by the upper energy release. it looks like it was sandwiched between two massive energy releases.

This map shows the current earthquake and historical instances:

Here’s the explanation:

The largest energy release occurred on segments that are known to have generated tsunamis in the past (blue contours). The patch of the Mw 9.0 earthquake close the epicentre overlaps with the source regions of the 1915, 1936, and 1978 tsunamis. [It goes to do more historical comparison]

What struck me about this is that earthquakes that caused tsunamis have historically happened at sea while in this instance, the landmass was directly impacted by both the earthquake and the tsunami resulting from it. That seems a unique situation, though the page doesn’t say it is.

I may be on to – well, nothing here, but it’d be great to hear from other seismologists, who, you know, actually know something, on this.