Four Cities Forecast: California Update July 28, 2010

The charts below are an update of the four cities forecast for California.  Previous updates to this forecast can be found in postings on July 8, 2010 and July 23, 2010.  Detailed explanations and details of how to read these charts can be found there. 

This update is a part of a continuing series of postings for earthquake forecasts for major cities in California and around the world that are subject to earthquake risk.  The figure below shows the probability in % that a magnitude M>7 earthquake might occur within 150 miles of the indicated city, within 1 year from now.  To better facilitate comparison, these figures are plotted together.  As the reader can see, the probability generally increases until a major earthquake occurs (blue dot), at which time the probability decreases suddenly.  Bursts of small earthquakes within the 150 mile circle lead to sudden increases of probability, while large earthquakes just outside the circle can lead to decreases in probability.

The figure above provides a good view of the long term change in probability, but what about the short term, say, over the past weeks and months?  To convey this information, we provide the table below, which gives the probability in %  in the first column with numbers, and the change in today's probability from its value 1 week ago, 1 month ago, 3 months ago, 6 months ago, 9 months ago, and 1 year ago.  Readers of this post should compare the values in the table below to the values in the last posting of July 23, 2010.  It can be seen that systematic changes are occurring as time passes, as also reflected in the figures above.