Moderate Earthquakes under Berkeley, California

john's picture

On October 20, 2011 two moderate earthquakes struck beneath Berkeley, California at depths of 9 to 10 km. The first of these events registered a magnitude of 4.2, with the second one a 3.8.  While small to moderate, these events were apparently felt as far away as Portland, Oregon.  

Similar magnitude earthquakes have been felt at this location, which is essentially at the boundary between the locked and creeping sections of the Hayward Fault.  In 1868, the Hayward was the fault upon which a magnitude 7 earthquake occurred, a repeat of similar such earthquakes in the past.  Seismologists are concerned that we are approaching another such event sometime in the next decade or two, inasmuch as the average recurrence time for these events has been estimated at 160 to 200 years.  

A question arises as to whether these events have increased or decreased the probabilty of a much larger event.  So we take this opportunity to compute a four cities forecast, similar to those posted on this site in the recent past, for the cities of San Francisco, Sacramento, Berkeley, and San Jose.  Conditions for the forecasts are simlar to those posted previously.  These forecasts are probabilities (chance of an earthquake in percent) for an event larger than magnitude 6 during the next 12 months, within a radius of 100 miles from each city.  Note that the previous such events were the 24 April, 1984 Morgan Hill earthquake (Magnitude 6.2) and the October 17, 1989 Magnitude 7 Loma Prieta earthquake.  

From the charts below, it can be seen that there is a roughly 1 in 4 or 1 in 5 chance of such an earthquake in the next 12 months.  



jordanss123's picture

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Guillermina T's picture

Around the world, the number of states is really damage because of natural earth quakes and that is real mass. Number of people get injured badly and they need the shelter and the aid from other countries to save them. Thanks for sharing such informative superiorpapers review content with us about the moderate earthquake under Berkeley California.

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