A tsunami generated by a massive earthquake off the coast of Alaska would force about 750,000 California residents to evacuate, would damage or sink one-third of the boats in marinas statewide and inundate low-lying areas of Los Angeles and Orange counties, according to a report released today.
The report, released by the U.S. Geological Survey, examines the consequences of a simulated tsunami sparked by a magnitude-9.1 quake that strikes of the Alaskan coast around midday on March 27, 2014.
Such a tsunami would force 750,000 people to evacuate, including about 90,000 tourists and visitors. That number would swell to more than 1 million if the quake were to occur in summer, when California beaches would be far more crowded, according to the report.
"The good news is that three-quarters of California's coastline cliffs, and thus immune to the harsher and more devastating impacts tsunamis could pose," according to Lucy Jones, the USGS science adviser for risk reduction. "The bad news is that the one-quarter risk is some of the most economically valuable property in California."
With waves surging into coastal marinas, one-third of the boats harbored there would be damaged or destroyed, resulting in an estimated $700 million in damage, according to the report. Low-lying portions of southern Los Angeles County -- notably Long Beach -- and northern Orange County would be inundated with water.
Waves would reach the shore relatively quickly, with tsunami effects hitting as far south as San Diego within about six hours, the report estimated, making evacuations tricky.
"Some island and peninsula communities and low-lying landfill islands within the ports could provide serious evacuation challenges because of limited exit options and short warning time prior to expected inundation," according to the report. "Evacuations would also be a challenge for dependent-care populations such as patients in hospitals and nursing homes and children in day care facilities. Education and planning tailored to each of these communities would be required to make tsunami evacuations successful."
Jones said the report is aimed at helping the state be more prepared for a catastrophic event.
"In order to effectively protect communities from tsunamis, we must first know what to plan for," she said. "By starting with science, there is a clearer understanding on how tsunamis function and their potential impacts. this 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."