john's blog

On July 30, this author published a blog on this web site giving the probabilities for major earthquakes having magnitudes M>6.7, within 12 months from July 30, 2010, within 150 miles, and for shallow depths of less than 30 km (most potentially destructive conditions), for each of four cities in Japan: Tokyo, Osaka, Niigata, and Sendai.  At that time it was found that probabilities (chance of an earthquake) were the highest near Tokyo, with the second-highest chance near Sendai.

The magnitude 6.3 Canterbury, NZ earthquake that occurred on 22 February, severely damaging much of Christchurch, serves to remind all of us that major earthquakes can occur at any time, potentially affecting many major cities around the globe.  Since July 2010, we have been periodically updating the time dependent probability of major earthquakes in California near four of its principal cities, using an experimental new methodology.

Yesterday's magnitude 6.3 earthquake near Christchurch, NZ was the second major earthquake to strike that city in the past 6 months.  The previous event was the magnitude 7.1 earthquake that occurred on 4 September, 2010. 

The four cities forecast for California is the probability of experiencing a major earthquake having magnitude > 7 during the 12 months from now within 150 miles of the four cities shown.  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 afterward.  Detailed explanations and details of how to read these charts can be found there.

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.

It can be seen that the forecast for San Diego is 0.2% (20 basis points) higher than on July 23, 2010, due to the continuing small earthquake activity.  For Los Angeles, it can be seen that the current forecast is 0.05% (5 basis points) higher than on July 23, 2010.

Previous posts in this series have shown a new type of experimental forecast for 4 major California cities exposed to seismic hazard.  These forecasts are made in real time and will be updated frequently.  In this posting, we extend these forecasts to 4 major cities in Japan.  Future postings will develop forecasts for some of the world's other megacities (populations of millions) in seismically active regions.

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. 

In earlier postings, we have shown examples of some new kinds of forecasts that give promise for better capturing the time dependence of earthquake probabilities and forecasts of future activity. Again, these foreasts should be regarded as experimental at this time.  These were posted on July 8 and July19, 2010.  In this post we continue this process by posting a comparison of 1 year experimental forecasts for four California cities, together with a table that provides numerical comparisons.  

In a blog posted on July 8, 2010 ("A New Type of Forecast') we provided figures showing the time history of magnitude M>7 earthquakes within 150 miles of San Diego and within 1 year of the time indicated on the horizontal axis. 

it seems timely to update that figure, and to provide another such forecast for the Los Angeles area.