http://mv-voice.com/print/story/print/2011/03/25/rating-our-risk-of-a-quake


Mountain View Voice

Opinion - March 25, 2011

Rating our risk of a quake

As they continue to contribute toward relief efforts for the victims of the earthquake and devastating tidal wave that struck the northeast coast of Japan on March 11, Mountain View residents are keeping a wary eye on the local fault lines that could create a similar disaster.

But although the San Andreas and Hayward faults might give the Peninsula or East Bay an up to 8.0 shake at any moment, scientists at the U.S. Geological Service in Menlo Park say fears of a tsunami roaring down San Francisco Bay toward Shoreline and other coastal areas of Mountain View are unfounded.

Scientist Tom Brocher, director of the USGS earthquake science center in Menlo Park, said that the San Francisco Bay's narrow opening and its shallow depth make it highly unlikely that a significant tsunami would be generated by either the San Andreas or Hayward faults.

Unlike the slightly less dangerous San Andreas and Hayward "strike-slip" faults, whose plates move parallel to each other, the Japanese earthquake was caused by a subduction zone fault, when two tectonic plates met and one was forced beneath the other.

When the faults experience a major shift underwater, the seabed can suddenly drop or rise, displacing huge amounts of water that can generate a tidal wave, he said.

But geologists are quick to point out that residents need to focus their preparations on earthquakes, particularly on the San Andreas fault, which has spawned two smaller faults, one named Monte Vista, that run through parts of Mountain View. But damage from these small faults would be minimal, geologists say.

With a quake of up to 8.0 magnitude from the San Andreas fault, the city's focus must be on making sure its buildings are able to withstand such a shaking. Dr. Tom Holzer of the USGS office in Menlo Park said that structures built in the 1970s and later are generally able to withstand a good shake.

The new El Camino Hospital is a good example of how modern technology can be used to build large structures that can withstand large quakes. Ken King, the hospital's administrative services officer, told the Voice that the hospital's foundation extends 9 feet underground and that the huge columns that support the five-story structure are sunk five feet into the foundation.

The hospital's upper floors are designed to move with an earthquake to absorb the energy, King said. "Anything that moves within the building is designed to move without crashing into any other part of the building."

For the thousands of city residents who are not in the hospital during a quake, the best way to cope is to be prepared. The old Boy Scout motto is the best advice for families and whoever is concerned about emergency preparedness.

The Mountain View Fire Department has plenty of information and can be reached at 903-6365. The department can help devise a plan that could make all the difference if a major quake struck the city. Residents can sign up to receive automated county alerts on their phone or cell phone, and follow the fire department on Facebook and Twitter, where emergency information would be posted.

Mountain View is sure to feel it the next time the San Andreas Fault shakes the Peninsula. No one can predict when or how strong the next earthquake will be, but residents can be reasonably sure that a tsunami will not flood the city, and that a magnitude 9.0 shake is probably not in the cards either.

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