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Tsunami 15.2 HAZARD PROFILE 15.2.1 Past Events Table 15-1 lists known tsunami events that have struck the County or one of its jurisdictions since 1859. The California Department of Conservation maintains a list of tsunamis in the state, including San Francisco or other Bay Area entities. Some tsunamis have struck San Francisco or other parts of the Bay Area but not San Mateo County; those events were not identified in Table 15-1. Table 15-1. Tsunami Events in San Mateo County Date FEMA Declaration Description Number San Mateo County Designated? September 24, 1859 N/A N/A A tsunami originating in Northern California hit Half Moon Bay, with a waves 4.6 meters high. April 1, 1946 N/A N/A An M-7.3 earthquake in the East Aleutian Islands (Alaska) triggered a tsunami that struck California. Wave heights of 2.6 meters were recorded in Half Moon Bay. May 22, 1960 N/A N/A An M-9.5 earthquake in Central Chile triggered a tsunami that reached San Mateo County. Wave heights of 1.2 meters were recorded in Pacifica. March 28, 1964 N/A N/A An M-9.2 earthquake off the Gulf of Alaska triggered a tsunami that reached San Mateo County. Wave heights of 1.4 meters were recorded in Pacifica. The tsunami arrived in San Francisco 5 hours and 6 minutes after the triggering event. February 27, 2010 N/A N/A An M-8.8 earthquake in Central Chile triggered a tsunami that reached San Mateo County. Wave heights of 0.6 meter were recorded in Half Moon Bay. March 11, 2011 DR-1968 No A magnitude 8.9 earthquake near Honshu, Japan generated a tsunami significantly affecting California on March 11, 2011. Wave heights were recorded at 0.7 meters in Half Moon Bay and 1 meter in Pacifica. The tsunami damaged six boat slips and three docks, and snapped a wooden piling at the Berkeley Marina. Sources: FEMA, NOAA Storm Events Database, California Department of Conservation More than 80 tsunamis have been recorded or observed in California, according to state records; however, many of these events were small and led to little or no damage. All tsunamis from the past century have been distant, not local. That is, they have all resulted from earthquakes far across the Pacific basin (as opposed to earthquakes near the American coastline). The most noteworthy tsunamis in California include:  January 26, 1700 (Local Tsunami)—An estimated M-9 earthquake ruptured the entire length of the Cascadia Subduction Zone, causing tsunami waves up to 50 feet in parts of northern California. Scientists have reconstructed the event from geologic evidence and oral Native American histories, as well as Japanese documents describing a tsunami that hit Japan’s coastline that same day.  December 21, 1812 (Local Tsunami)—A tsunami struck the Santa Barbara and Ventura coastlines not long after an earthquake was felt in the area. The tsunami inundated lowland areas and damaged local ships. Some debate exists as to whether the tsunami was earthquake-induced or the result of a submarine landslide triggered by the earthquake.  April 1, 1946 (Distant Tsunami)—An M-8.8 earthquake in the Aleutian Islands generated a tsunami that caused damage along the coast of California, including flooding more than 1,000 feet inland in Half Moon Bay. 15-3