In-Depth: Tsunami danger lurking off San Diego coast

Report says CA fault lines could cause tsunamis
Preparing for a tsunami in San Diego
Posted at 5:52 AM, May 17, 2021
and last updated 2021-05-17 14:14:41-04

SAN DIEGO (KGTV) - San Diego's coastline is more susceptible to a tsunami than previously thought.

A new report in the Proceedings of the National Academy of Sciences of the United States of America says that strike-slip faults found along the California coast could cause tsunamis.

It was previously thought that only subduction zone faults created tsunamis.

A subduction zone is where one tectonic plate moves underneath another. In an earthquake along one of those faults, the ground either rises or falls dramatically. When that happens in the ocean, it often displaces a large amount of water, leading to a tsunami.

In strike-slip faults, like the San Andreas or Rose Canyon fault in San Diego, tectonic plates crash into each other or move alongside one another.

Those kinds of earthquakes aren't thought to cause tsunamis. But the new report points to events like the 2018 earthquake and tsunami in Palu as proof that it can happen.

"For the people of San Diego, it shows us that we have the potential of having tsunami, located close to shore, rather than things that just come from 1000s of miles away," says San Diego State University geology professor Dr. Pat Abbott.

Tsunamis in San Diego are rare, with only 11 happening in the last 100 years, and most of them coming from earthquakes that occur in Japan, Chile, or Alaska.

But there have been four tsunamis in Southern California created by local earthquakes.

Geologists say an earthquake with a magnitude higher than 7.0 on the Richter scale could generate tsunami waves as big as four feet. That wouldn't create the kind of devastation we saw in past tsunamis from Japan or Indonesia. Still, it would do some damage to boats and businesses in the harbor or one of San Diego's bays.

"That would cause boats and ships to be broken away from their moorings or maybe cause swimmers to have difficulties swimming," says NOAA Meteorologist Alex Tardy. "It could even make it impossible for a boat to enter a harbor or even leave a harbor."

In 2017, San Diego lifeguards added new signs to danger zones, warning people about tsunamis and what to do if they feel an earthquake.

RELATED: Lifeguards unveil new beach signs for tsunami awareness week

Abbott says the best advice is to seek higher ground if you feel the earth shake.

"If you feel a big earthquake, you don't want to be standing at the waterline," Dr. Abbott says. "Let's get some elevation. Let's go up a floor in a building or climb up a hill or something."

For more earthquake and tsunami readiness information, visit