California updates data, plans for tsunami danger
03/22/11
A huge tsunami generated by a powerful earthquake in Alaska's Aleutian Islands could threaten harbors and shorelines of 100 California cities and towns and 20 counties, the state's tsunami specialist warned Monday.
Rick Wilson, an engineering geologist with the California Geological Survey, said scientists at the survey and disaster management specialists are surveying harbormasters in every port city in the state to determine in detail the effects of the tsunami that hit the coast on March 11 after the magnitude 9.0 earthquake in Japan.
They were also to develop new evacuation routes for the future.
Damage to California's coastal communities has now reached $40 million to $50 million, Wilson said. The tsunami was particularly damaging to the harbors of Crescent City (Del Norte County) and Santa Cruz.
Wilson's agency, which two years ago published an "inundation map" series online for every county in the state, is now planning similar maps to help land-use planners assess hazards to buildings near shores and harbors, and to provide a guide to danger zones where new construction might be avoided, he said. The new maps will not be ready for a year or two.
The state Geological Survey has also added a feature to its tsunami inundation map site that allows people to see the probable flooding areas near a specific address.
Marin County has a site that shows the probable flooded areas for every town and includes a narrated video with information and advice about tsunamis, plus the addresses and phone numbers of all emergency services.
The maps are based primarily on what would result from a magnitude-9.2 earthquake in the Aleutian Islands. That would be a "worst case scenario," Wilson said in a telephone briefing with reporters Monday.
Scientists at the U.S. Geological Survey consider an earthquake of that size a thousand-year quake - meaning such a temblor might occur only once in a thousand years. A 500-year quake or a 100-year quake would be much smaller and cause a less powerful tsunami.
But, Wilson said, in preparing for any tsunami - especially in building along the coast or planning evacuation routes, it's safest to plan for the "worst-case scenario."
What might flood in a tsunami
The state Geological Survey has developed an online feature that allows people to see probable flooding areas near a specific address after a tsunami. Check it out at links.sfgate.com/ZKXJ.
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