New tsunami hazard maps highlight threat facing seven California counties — even Napa Valley
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The threat of a major California earthquake is growing in the region’s seismic zones of San Francisco, San Mateo and Napa counties and even a cluster in the Napa Valley.
Seismologists from the U.S. Geological Survey are working furiously to prepare after the Feb. 5 quake in Japan that triggered powerful tsunami waves, killing nearly 18,000 and sending waves of up to 13 feet across much of northeast Japan.
The U.S. Geological Survey (USGS) is working with state regulators to assess tsunami threat in the California region, where the majority of earthquakes are felt.
On Tuesday, the USGS prepared a new set of tsunami hazard maps for earthquake zones in Northern, Central, Southern and Pacific regions — a first for the U.S.
“It is a very, very different map (from the existing one) — so it might help us better prepare,” said Susan McManus, USGS seismologist.
The new hazard maps highlight where the most tsunamis could reach and the highest risk in the event of an earthquake.
Among the highlights are:
• The San Mateo County coast: As of August 2010, there was a 29 percent chance a large earthquake could trigger a tsunami.
• The San Francisco/Modesto County coast: As of December 2011, there was a 33 percent chance a large earthquake could trigger a tsunami.
• The Napa Valley: As of December 2011, there was a 70 percent chance a large earthquake could trigger a tsunami.
• Point Alvarez/Salinas: As of August 2010, there was a 46 percent chance a large earthquake could trigger a tsunami.
• Point Cabrillo/Pacifica: As of December 2011, there was a 46 percent chance a large earthquake could trigger a tsunami.
The maps are based on studies of past earthquake zones in California’s seismic zones of San Francisco, San Mateo, Napa and Sonoma counties.
The map for Point Cabrillo/Pacifica was prepared after the January 7 earthquake in this cluster, which sent waves up to 20 feet across the
