Logo: University of Southern California

Viterbi Experts Redraw State Tsunami Hazard Map

350,000 Californians at potential hazard from earthquake-driven sea waves, study finds
Eric Mankin
December 21, 2009 —

Venice-Marina del Rey - Playa del Rey area of Los Angeles county inundation map. Red area is at risk. (Click on map to read recent Scientific American story on study)
Costas Synolakis, Jose Borrero and Aggeliki Barberopoulou of the USC Tsunami Research Center provided basic research for a new set of inundation maps recently released jointly by USC, the California Geological Survey, and the California Emergency Management Agency.

The large scale (1:24,000) maps, accessible online on the California Department of Conservation website, show all the coastal counties in the state, from Del Norte in the north to San Diego in the south.

On each map, a red line shows the best estimate for "the largest anticipated tsunami event, plus a high tide," according State Geologist John Parrish of the California Geological Survey, who presented the maps at a San Francisco meeting of the American Geophysical Society shortly before the fifth anniversary of the Dec. 26, 2004 Indian Ocean tsunami.

Borrero of the Astani Department began the actual painstaking computer simulations that made the calculation, work later taken over and completed by Barberopoulou working with Synolakis.

Detailed simulation is required because tsunami effects are heavily dependent on the orientation of the coastline (whether or not it faces likely earthquake areas) the shape of the shoreline (some formations can focus waves as they come ashore, making the crests higher); and the local topography near the ocean (hilly coasts are safer than beaches with flat topography). When all the factors combine to maximize impact, the waves can be as high as 45 feet in Crescent City in Northern California.

Angel 1
Simulator-in-chief Aggeliki Barberopoulou on at-risk Venice beach

Some 350,000 Californians live in areas subject to potential inundation, according to the study.

Work on the project was motivated by the 2004 events: "Post-Sumatra, we started considering events that are all along the Pacific Ocean," said Synolakis at Sign 1the San Francisco presention.

Others working on the project along with Barberopoulou, Borrero and Synolakis included Burak Uslu of the NOAA Pacific Marine Environmental Laboratory, Nikos Kalligeris of the Technical University of Crete, Greece,, James D. Goltz of the California Governors' Office of Emergency Services, and Richard I. Wilson of the California Geological Survey.