Japan Four Cities North Forecast: April 12, 2011, Magnitude > 6

In previous blogs, this writer has focussed on larger earthquakes, those having magnitudes M>6.7 and M>7.0  In this and the companion blog, we compute the probabilities for M>6.0 earthquakes in the "south-central" four cities of Miyazaki, Tokushima, Osaka and Nagasaki. 

Here we show probabilties (chance of an earthquake in %) for the four "north" four cities of Tokyo, Nagoya, Niigata and Sendai. Even though these probabilities have been optimized through backtesting, they appear to this writer to be too small, that is, the actual probabilities are likely to be higher.  The reason is that, as explained previously, the probabiities are calculated by counting the number of earthquakes having magnitudes M>4 since the last M>6 large earthquake.  However, there have been so many M>4 earthquakes since March 11, that it is unlikely that all of the M>4 events were included in the ANSS catalog.  Thus, the computed probabilities are likely to be too low since March 11.  This writer would estimate that the actual probabilities since March 11 are likely to be at least twice as large as those shown here.

iHere is the data, presented as usual in both time-series (line chart) format and table format.

Here are the probablities in table form.