About that M>8 Earthquake Near Japan (Technical)
To further investigate the data underlying the forecast, we defined a polygon of (lat,long) pairs around the main islands of Japan. These (lat,long) pairs are given by: (34.3,128.2), (38.0,136.8), (45.6,141.0), (42.9,147.7), (32.0,145.5), (27.5,131.5). These were entered into the ANSS User Interface. We found the following for the earthquakes occurring from just after the M9.1 event on 3/11/2011 through 12/29/2012 (Note that there is no data in the catalog from 12/30/2012 through today, 1/28/2013): 911 events with M>5; 94 events with M>6; and 6 events with M>7.
For the purposes of this discussion, we will assume the global average for the Gutenberg-Richter b-value, b=1. Then for every M>8, we would expect to see 1000 M>5 earthquakes, 100 M>6 earthquakes, and 10 M>7 earthquakes. The actual data are a reasonable approximation to the expected numbers. What seems to be missing is the M>8 event.
About OpenHazards Bloggers
Steven Ward is a Research Geophysicist at
the Institute of Geophysics and Planetary Physics, UC Santa Cruz. He specializes in the quantification and simulation of
natural hazards. Read Steve's blog.
John Rundle is a Distinguished Professor of Physics
and Geology at UC Davis and
the Executive Director of the APEC Collaboration for Earthquake Simulations. He
chaired the Board of Advisors for the Southern California Earthquake Center from 1994 to 1996. Read John's blog.