Tsunami hazard maps updated by CA Geological Survey for counties in the Four Bays Area



The California Geological Survey (CGS), which is a branch of the California Department of Conservation, recently updated its tsunami hazard maps that affect Marin, Sonoma, Napa and Solano counties, showing an increased risk of inland flooding. for each of them.

Since 1850, approximately 50 credible tsunamis have been recorded or observed in the San Francisco Bay Area. The most severe tsunami wave to ever hit the Bay Area occurred on April 1, 1946, when a magnitude 7.4 earthquake off Alaska triggered a massive tsunami that sent waves up to 15 feet high crash into the shores around Half Moon Bay.

After the Hunga Tonga-Hunga Ha’apai volcano triggered a global tsunami warning in January this year – the volcanic explosion possibly the most violent eruption ever captured by satellite – deep waves of displaced water have started moving to the West Coast, including the Bay Area. . Although the National Weather Service reported that the tsunami’s peak waves were around 2 feet, widespread flooding was seen in the Bay Area; it caused over $10 million in damage. This latest tsunami, the most recent in the region, has shown how vulnerable we are to sudden ocean swells, as well as sea level rise.

And for the first time since 2009, the CGS updated its tsunami hazard maps for the state, which included changes in seven counties.

In updated maps released on Friday, four of the seven countries that were refreshed were located in the Bay Area: Marin, Sonoma, Napa, Solano, Santa Cruz, San Diego and Ventura counties were all included in the update. up to date. (A quick scroll through the map directories shows that Alameda, Santa Clara, San Mateo, and Contra Costa counties were all updated in 2021.)

Maps show that a large tsunami could send seawater into parts of the Napa County airport; flooding from a tsunami would affect many areas of the Petaluma Valley; Sausalito would be almost entirely consumed by a powerful tsunami – and the small town of Bolinas would suffer a similar fate.

As for us here in San Francisco, the steep hills and elevation of our city spare us absolute destruction. According to these tsunami hazard maps, many neighborhoods east and north of Golden Gate Park will be spared catastrophic flooding. However, areas of the city that are closer to the sea – like the Embarcadero, Hunters Point, and parts of SoMa – could very well be swallowed by the ocean in case a large tsunami rushes our way.

The fact is, we are more likely to experience a huge tsunami than the Big One in our lifetime. Now might be a good time to make sure those emergency kits are all ready.

You can view the updated interactive tsunami hazard maps below:

Related: New tsunami impact map for SF puts North Beach and Lower Market Street under water

Photo: Courtesy of Getty Images/Lemaneih

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