New tsunami hazard maps highlight threat facing seven California counties — even Napa
Tsunamis can be deadly, even in isolated regions. Now, scientists have created the very first map of the current U.S. coastal hazard zone, with risk maps pinpointing danger facing residents in San Francisco, Los Angeles, Orange and even Napa — even under a dry year.
The maps, based on computer models that simulate tsunamis hitting the coasts, come as California officials grapple with a major risk of a statewide disaster if a powerful earthquake strikes at this time.
The maps show what the coast looked like before a 6.7 quake in Kobe, Japan’s fourth-largest city, which occurred at 11:20 p.m. on Friday, Aug. 11, 2012. The quake triggered a tsunami that struck the coast at high tide, destroying most of the coastal communities and killing more than 2,800 people.
The map at the top shows a tsunami with 1ft (0.3m) waves heading for San Francisco, Los Angeles or Orange County, California. The coast will be hit no matter which direction it is coming from.
This map shows tsunami wave heights going up the coast, which is in the same general direction as the earthquakes. The tsunami wave heights in the models ranged from 2 ft. (0.6 m) to 20 ft. (6.1 m).
The risk is greatest in the San Francisco Bay Area, where the Pacific plate is moving northward under an active fault, potentially causing a devastating earthquake and tsunami.
The maps do not consider tsunami height — the most dangerous aspect of the model — and they do not take into account additional scenarios such as a tidal bore or the possibility of large aftershocks from an earthquake.
The tsunami models used to generate the maps were run using information about movement in the Earth’s crust and plates, which can be combined with data about the ocean floor from seismic and drilling research.
For instance, if the plate bearing the fault is moving northward, this would mean that the quake was in the same general direction as the tsunami, although