Report: Future Tsunami Could Swamp Coastal Areas

Byline: Associated Press/Alicia Chang

LOS ANGELES (AP) — If a monster earthquake struck off Alaska’s coast, tsunami waves would rush toward California, crippling the nation’s busiest port complex, flooding coastal communities and causing damage to as many as one-third of the boats in coastal marinas, a report released Sept. 4 suggests.

The potential impacts, based on a hypothetical magnitude-9.1 jolt off the Alaskan peninsula, were detailed by a team led by the U.S. Geological Survey (USGS) to help emergency responders prepare. Their report — the USGS Science Application for Risk Reduction (SAFRR) Tsunami Scenario — looks at the potential economic impacts, affects on coastal marinas and suggested preparations for evacuations.

Tsunamis are a rare but real threat in California. After the 2011 Japan disaster, tsunami waves raced across the Pacific and damaged boats and docks in the commercial fishing village of Crescent City.

Scientists said a closer offshore quake would create more havoc. The twin ports of Los Angeles and Long Beach could be shuttered for at least two days because of strong currents, potentially losing $1.2 billion in business.

In addition, pleasurecraft marinas would be inundated — and coastal communities would face mass evacuations, the report said.

In the 9.1-magnitude Alaska quake scenario, approximately 750,000 people would need to be evacuated, with 90,000 of those being tourists and visitors. Additionally, one-third of the boats in California’s marinas could be damaged or completely sunk, resulting in $700 million in losses.

It was concluded, however, that it was unlikely that any of California’s nuclear power plants would be damaged by this particular event.

Over the past two weeks, coastal planners have held meetings around the state to digest the information and review their evacuation plans.

Under the scenario, it would take about four hours for tsunami waves to crash into communities near the Oregon state line and about six hours to reach San Diego — theoretically, allowing time for people to flee to higher ground. The force of the waves would sink boats that remained docked in marinas and would damage harbors.

This “helps them understand what a bad tsunami can be,” said USGS seismologist Lucy Jones.

The team began work on the scenario before the magnitude-9.0 earthquake that struck Japan in March 2011 and triggered a tsunami. It went back to the drawing board after seeing the toll on Crescent City and other coastal cities. The group focused only on California, even though a powerful offshore Alaska quake would affect the West Coast.

Patrick Corcoran, an Oregon State University expert on earthquake and tsunami hazards, praised the scenario for being realistic. But he said it’s a challenge to prepare people for a rare disaster.

“People just go into freak-out mode” when past tsunamis have hit the U.S., said Corcoran, who had no role in the report.

The latest scenario is similar to a quake exercise released several years ago designed to prepare California residents for the “Big One” on the San Andreas Fault. Unlike the quake report that estimated 1,800 casualties, scientists did not include a death toll this time, since they could not predict how evacuations would be handled during a tsunami.

Since 1812, the California coast has seen only a handful of tsunamis with waves higher than 3 feet. The deadliest occurred in 1964, when a magnitude-9.2 quake in Alaska triggered tsunami waves that killed 12 people in Northern California.

The SAFRR Tsunami Scenario is a collaborative effort of the USGS, the California Geological Survey, the California Governor’s Office of Emergency Services, academic institutions, the National Oceanic and Atmospheric Administration and other agencies and institutions.

“The good news is that three-quarters of California’s coastline is cliffs, and thus immune to the harsher and more devastating impacts tsunamis could pose,” said Jones, who is the USGS Science Advisor for Risk Reduction and leads the SAFRR Project. “The bad news is that the one-quarter at risk is some of the most economically valuable property in California.

“In order to effectively protect communities from tsunamis, we must first know what to plan for,” Jones said. “By starting with science, there is a clearer understanding on how tsunamis function and their potential impacts. The scenario will serve as a long-lasting resource to raise awareness and provide scientifically-sound and unbiased information to decision makers in California and abroad.”

— Additional information was provided by USGS