Alaska 1964 Good Friday earthquake and tsunami damage, photo via NOAA.
The California Geological Survey has updated its tsunami risk maps for Pacifica and other towns to the south for the first time since 2009. New data and computer modeling predict a heightenend risk to coastal neighborhoods.
The Pedro Point and Linda Mar shopping centers and Rockaway Beach Plaza fall within the map's tsunami evacuation zone, as does the entire Linda Mar neighborhood all the way to Cabrillo School. Sections of Pedro Point near the beach are also in the danger zine, as is the western part of the Fairway Park neighborhood
Mori Point, and the Sharp Park Golf Course are also in the evacuation zone, but Eureka Square Shopping Center, is in the clear.
To find out whether your home is in the evacuation zone, punch your address into this interactive map:
Historically, Pacifica has stayed relatively safe from tsunamis. According to the City of Pacifica website:
The Channel Islands were hit by a big tsunami in the early 1800s. The worst resulted from the 1964 Alaskan earthquake and cause 12 deaths and at least $17 million in damages in northern California. The 1992 Cape Mendocino earthquake produced a one-foot tsunami that reached Humboldt Bay about 20 minutes after the shaking. Although not damaging, the tsunami demonstrated that locally generated tsunamis can reach the California coastline quickly. Had the earthquake lasted longer, the wave heights would have been higher. Evidence suggests that large earthquakes capable of producing local tsunamis recur every two or three hundred years.
If an earthquake-causing tsunami happens far away, authorities usually have time to issue warnings. The CGS estimates that a worst-case scenario magnitude 9.3 earthquake in the eastern Aleutian Islands off Alaska would take about five hours to reach the San Mateo coastline.
But if a strong earthquake occurs in the ocean close to the coast, there may not be time for a warning.
Earthquakes longer than 20 seconds typically cause tsunamis, so to know whether a tsunami might follow an earthquake, count to 20 when you begin to feel the shake.
To see an interactive tsunami map for all of Calilfornia click here.