Friday, March 18, 2011

Preliminary analysis of Japan Earthquake March 2011

Greetings from "Earthquake of the Week" at the Australian National University Research School of Earth Sciences in Canberra. This weekly event is very well attended as the topic is the analysis of the recent Japan Earthquake. I am not a seismologist, but as I understand what I am being told, this earthquake was over a larger distance: 100 km, compared to a more usual 38 km. Essentially these were four large earthquakes in quick succession in the same area. In other respects the earthquake was not unusual for the area.

The Tsunami arrived on shore about 25 minutes after the earthquake. This provided very little time for evacuation. There would be few places to escape from a 15 m wave. Unlike an earthquake, survivors will be scattered around a debris filed away from where they were. Mobile phones are unlikely to be functioning after immersion.

The latest data indicates that there is n way to predict if, when or where very large earthquakes will occur.

The Fukushima nuclear power plant was designed for an 8.2 magnitude earthquake. It survived the much larger earthquake well. Japanese nuclear power plants automatically shut down when an earthquake is detected. The Fukushima reactor had a 3m high wall around it to prevent a tsunami expected from a 8.2 earthquake. However this was over-topped by the much larger wave which damaged the emergency power supply.

The Japan Atomic Industrial Forum has detailed reports on the situation. At present it appears little widespread risk to the public. There is a literature on this field, such as: Analysis of impacts of wind integration in the Tamil Nadu grid Energy Policy, Volume 37, Issue 9, September 2009, Pages 3693-3700 Mel George, Rangan Banerjee.
Every Friday, the seismology and mathematical geophysics group holds a meeting, popularly called "Earthquake of the Week", where we discuss our research, relevant papers and weekly global seismicity.

This week happens to be of a special interest due to an unfortunate combination of great earthquake and tsunami that hit Japan, and we will most likely dedicate our entire meeting to this event with two or three presentations and discussions. ...

Hrvoje Tkalcic
Fellow in Seismology/Earth Physics
Research School of Earth Sciences
The Australian National University

1 comment:

Tom Worthington said...

Hrvoje Tkalcic commented 19 Mar 2011 13:29:13 +1100 (EST)L

This week's meeting was successful due to a great interest of various people in the Tohoku earthquake and tsunami. Normally, our
meetings only consist of group members discussing our research,
papers and weekly seismicity.

I notice that in your blog you mentioned the dimensions of the rupture zone - the numbers you mentioned refer only to the vertical extent of the rupture. This one went very deep, down to 100 km or so, whereas most other great arthquakes are limited to only 35 km or less.

However, the lateral extent of the rupture was more like 400-450 km or so.

The surface of the rupture is directly proportional to the moment magnitude (energy release) of an earthquake. This explains why other great event are long but narrower in rupture extent. You can get the same surface by rupturing only 400 laterally, but down to 100 km vertically, as to what you get by rupturing 1200 km laterally and, say, 33 km vertically.

This is why Brian referred to this earthquake as a "fat one".

Thank you for your kind note and additional information.