The California Geological Survey has released updated tsunami hazard maps for seven counties to help users determine whether they are in areas at risk for inundation and for planning.
The revised interactive maps released Friday cover San Diego, Santa Cruz, Ventura, Marin, Sonoma, Solano and Napa counties.
The new maps reflect new data and improved computer modeling since an earlier series of maps was published in 2009, as well as threats from tsunamis originating far away and locally, the Geological Survey said in a press release.
In one example of the updates, new modeling for Santa Cruz County shows that a subduction zone earthquake off the Aleutian Islands could unleash a tsunami 18-25 feet (5.5-7.6 meters) above the Santa Cruz Boardwalk, more than double the height suggested in 2009, the agency said.
The Geological Survey said California’s shores have been struck by more than 150 tsunamis since 1800, and while most were minor, some have been significantly destructive and deadly.
On March 28, 1964, a tsunami triggered by a powerful earthquake in Alaska smashed into Crescent City, California, hours later. Much of the business district was leveled and a dozen people were killed.
More recently, a tsunami from a 2011 earthquake in Japan caused about $100 million in damage to California ports and harbors, and ocean surges from last January’s volcanic eruption in Tonga caused about $10 million in damage to harbors in Santa Cruz and Ventura counties.
The California Geological Survey is part of the state’s Department of Conservation.