Thursday, October 20, 2011

Just Gotta Love Days Like This...Earthquakes, Earthquakes, Earthquakes

I just love days like this...The Great California ShakeOut has people thinking about earthquakes all over the state of California, with upwards of 8 million people practicing and preparing for a major seismic event in the state. I just happen to be introducing the topic of earthquakes in my physical geology classes today. I just finished blogging about the myths of earthquakes in California. Then...two earthquakes just happen to shake the Bay Area! The events, registering magnitude 4.0 and 3.8, were felt across the region, but probably caused little damage. They took place on or near the Hayward fault, which is one of the major active fault zones in the state. It is capable of generating events in the magnitude 7 range.
The quakes today did a great job of making people aware of the seismic hazards of living in the state (and really...just HOW did the ShakeOut people arrange for actual earthquakes???). Few people were hurt, but everyone is talking about them.

There is a more ominous note in the quakes today. The Hayward fault is one of the most dangerous fault zones in California at this time, partly for the size of the quakes that it can produce, but even more for the level of urbanization along the trace of the fault. A magnitude 7 quake has the potential to kill and injure tens of thousands, and to cause untold billions of dollars of damage. The U.S. Geological Survey calculates a 31% chance of a 6.7+ magnitude quake along the Hayward within the next 30 years (and only a 21% chance along the San Andreas within the same time period).
Foreshocks may often precede a major earthquake, and there is a slight chance (maybe 5%) that today's events are precursor quakes. They are reminders that to live in California is to live in earthquake country, and that it is critical to be prepared. All Californians, and especially those in the urban centers of the Bay Area, Los Angeles, and the Inland Empire should always have spare water, food and first aid supplies handy, both at home and in their cars. Find out what the hazards are in your particular area. Have a family plan for when you are separated following a major event. Check out the Great ShakeOut website for more information.

Stay safe!
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