Myths and Misconceptions about California and Earthquakes for the Day of the Great Shake-Out!

Today is the Great Shake-Out in California: At 10:18 AM, around 9 MILLION people participated in a statewide earthquake drill. This is also the day after the 23rd anniversary of the Loma Prieta earthquake that caused so much damage in the San Francisco Bay-Santa Cruz region, and given that many people in northern California weren't even born by then, and others have moved in, it helps to be reminded that earthquakes are a fact of life in our fair state (and our state is quite fair because of the long-term activity of earthquakes: it's how our mountains formed). Last year I posted a series of assumptions that people sometimes make about California and earthquakes, and it seemed to be a good time to dust off some of these old posts...

It starts with a modest little quiz....

True or False?

• California is going to fall into the Pacific Ocean
• The San Andreas fault causes all California earthquakes
• California has more earthquakes and bigger earthquakes than anywhere else
• The ground opens up and swallows people during earthquakes
• Psychics and animals predict earthquakes
• We in California are waiting for the "BIG ONE"

Comic art courtesy of Zeo

The answers are pretty extensive, so click below to read more...

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!