Tsunami Risk

Birds Eye View Photos of San Onofre

Paleoseismic features show evidence of tsunamis and significant seismic activity in North San Diego County

Tsunami Hazards in the South Coast Region, Dr. Mark Legg, CSU Fullerton Daily Titan, September 29, 2011

Mark Legg, geologist and president of Legg Geophysical, appeared at a September 2011 CSU Fullerton Department of Geological Sciences seminar as a guest speaker for a lecture titled Tsunami Hazards in the South Coast Region.

In regards to earthquakes, the size of the tsunami depends on the earthquake magnitude, and these usually come from big thrust faults, Legg said.

But in Southern California we don’t have that (big thrust faults), but that doesn’t mean we don’ have dangerous tsunami faults,Legg added.

Most damaging tsunamis are caused by earthquakes of magnitude 7 or higher.

Legg said if there was an earthquake of magnitude 9 in the Aleutian Islands or in Samoa, the energy of the tsunami would be strongest traveling to San Diego in comparison to zones like Japan, the western coast of South America and parts of the eastern coast of Asia.

But you can’t outrun a tsunami, Legg said. The best method of surviving a tsunami is evacuating the beach city within two to three hours of the quake, even if the epicenter of the earthquake is not where you’re located.

When it starts getting knee-deep, which is a half a meter roughly, that’s when it starts to become potentially deadly, and if you add a bunch of debris, it’s even worse, Legg said.

Tsunami inundation map with references – CA Dept. of Conservation

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