TSUNAMI STUDY FINDS REGION AT RISK

A large tsunami hitting California would cause major flooding in Long Beach and parts of Orange County and force 750,000 people to evacuate coastal areas in just a few hours, according to an extensive simulation published Wednesday by the U.S. Geological Survey.

The study, released two years after a tsunami killed thousands in Japan, identified several communities that are particularly vulnerable to flooding because of their low elevation and lack of protection from waves.

They include Marina del Rey and the ports of Los Angeles and Long Beach as well as the low-lying coastal areas extending from the ports to Newport Beach.

The report, compiled by dozens of scientists, emergency responders and industry representatives, is the most extensive examination of what a tsunami would do to California’s coastline. The research simulated a 9.1 quake off the Alaska coast that would send damaging waves to California.

While waves would be larger in Northern California -- between 10 and 23 feet -- the damage could be greater in Southern California because the region has more coastal development and fewer coastal cliffs.

Tsunami waves of 3 to 10 feet could submerge blocks of Long Beach south of Ocean Boulevard, including the Aquarium of the Pacific and the Long Beach Convention Center as well as the Shoreline Village and Pike shopping centers. Those same-sized waves could cause flooding around the affluent communities of Newport Bay and Huntington Harbour as well.

California has been preparing for decades to deal with major earthquakes. But only more recently have officials begun extensive tsunami planning, including establishing evacuation routes in coastal cities. The research for the simulation was expanded after Japan’s tsunami focused more attention on the risk, said Lucy Jones, the U.S. Geological Survey seismologist who led the project.

“The idea is to say: Look, these are not distant events, these could actually happen here,” said Kathleen Tierney, director of the Natural Hazards Center at the University of Colorado Boulder. “This is meant to get tsunamis on the public’s radar.”

Under the study’s scenario, the first waves would hit Crescent City, in the far north of the state, in as little as four hours. The waves would then make their way down the coast, arriving in San Diego two hours later.

Researchers said the waters would cause sewage to foul beaches, damage fishing boats in marinas and make more than 8,000 people homeless.

Tsunamis could also travel several miles inland up coastal rivers. Statewide, one out of three boats in coastal harbors and ports could be damaged or sunk, and the cost of the disaster could approach $8 billion.

The biggest challenge would be evacuating everyone before the tsunami hits. Some areas, like Balboa Island in Newport Beach, have only narrow roads for escape routes.

During summer beach season, evacuation could be significantly more difficult. More than 250,000 people at beaches and coastal parks would have to evacuate in the spring. And that number jumps to 1 million in the summer.

“Your life depends on how you respond,” Jones said. “People die in tsunamis. They’re very, very deadly, but we do have time. We have a few hours.”

Unlike earthquakes, which millions of Californians can recall vividly, tsunamis are rare enough that few coastal residents have experienced them, making it difficult for local officials to know how seriously people might take evacuation warnings.

The study’s simulation involves a temblor that hits Alaska just before noon on March 27, 2014, which would be the 50th anniversary of the tsunami caused by a 9.2 earthquake in Alaska in 1964.

A tsunami as powerful as that created in the simulation is estimated to occur once every several hundred years.

There’s little recorded evidence of a destructive tsunami in Southern California in modern times. But the 1964 Alaska tsunami killed 10 people in Crescent City.

Other areas that could be inundated under this kind of tsunami include parts of Belmont Shore as well as Naples Island in Long Beach, portions of Sunset Beach and Seal Beach in Orange County, much of Balboa Peninsula and all of Balboa Island in Newport Beach, and Mission Beach in San Diego.

The Ports of Los Angeles and Long Beach would have to order immediate evacuations, and they would be left idle for as many as two days. The warning time the ports would receive in this scenario might not be enough to complete the vessel evacuation plan.

A toxic stew of ship debris and fuel and pesticide-laden runoff from flooded farms could take years to clean up.

Rich Baratta, the director of risk management for the Port of Long Beach, said damage to Southern California ports would be tempered by the fact that they actually face south, not west.

“There is a benefit to us in the sense that we don’t get the surges and potential damage that the ports get up in Humboldt and Northern California, because the mouths of their ports face the open sea,” he said.

Roads across the state could be damaged by a tsunami, including Pacific Coast Highway in Malibu and Orange County, Interstate 5 near Camp Pendleton, and Interstate 80 in Emeryville, just north of Oakland.

In Northern California, experts warned of damage to the Port of San Francisco’s headquarters and the Bay Bridge toll plaza in Oakland. Pier 39 and Fisherman’s Wharf are also in the danger zone. A tsunami could permanently wash away beaches in Malibu and Laguna.

Tsunamis have been an under-scrutinized hazard for years, particularly before the 2004 Sumatra tsunami and the 2011 Japan tsunami brought attention to the hazard.

A map of the inundation zones surmised under this tsunami scenario can be found at https://bit.ly/CA tsunamimaphttps://bit.ly /1a7LRVL.

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ron.lin@latimes.com

tony.barboza@latimes.com

hector.becerra@latimes.com