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.

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 1969 the famous Japanese seismologist Kiyoo Mogi (1929-) wrote a paper entitled:  "Some Features of Recent Seismic Activity in and near Japan.  Activity before and after Great Earthquakes."  Published in the Bulletin of the Earthquake Research Institute, Japan [1], it described patterns of smaller earthquakes that precede great earthquakes. 

An earthquake measuring 6.9 on the Moment-magnitude scale has struck southern Qinghai,
China, near the city of Yushu in the Tibet Autonomous Region.  Using the Hazard Viewer tool
on this web site, together with the Recent Earthquakes display, it can be determined that the ground
shaking resulting from the earthquake in Yushu was between 8% g and 12% g, equivalent
to Modified Mercalli Intensity V to VI.  Shaking of this intensity is enough to collapse some buildings
constructed of unreinforced masonry, as might be common in the region.

Aftershocks are earthquakes that are triggered by a previous, larger earthquake mainshock.  Today we know that aftershocks are a result of the transfer of stress from the region of the mainshock to surrounding, smaller faults.   About 5%-10% of mainshocks have foreshocks, which can be regarded as instances when the aftershock is larger than the mainshock.