SAN FRANCISCO – California doesn’t often experience dangerous tsunamis, but there is one type of marine surge that some experts are increasingly concerned about.
According to experts, disaster modeling and local hazard plans, tsunamis near land tsunamis – those caused by offshore earthquakes could pose particularly disastrous risks to California’s densely populated coastal communities.
Depending on the intensity and location of the earthquake, life-threatening waves can approach the coastline in just 10 minutes. Perhaps there isn’t even enough time for an emergency warning to be issued.
And it is a potential threat along California’s 840-mile coast, from dense cities to the south to more remote areas to the north.
Data published in both cities and counties in Los Angeles demonstrates how locally generated tsunamis can reach heights up to five feet above the average sea level in Marina del Rey. 7 feet in Manhattan Beach and San Pedro. 8 feet from Long Beach and Santa Monica Pier. 9 feet in Malibu. 30 feet on Catalina Island – depending on where rupture faults and underwater landslides are caused.
In Orange County, a magnitude 6.8 shaking offshore shore could bring local sauce tsunamis to the coast in just 15 minutes, county documents say. Earthquake-induced submarine landslides could flood areas of Newport Beach, including Balboa Island, the Balboa Peninsula and Ridoisle, and so far have potentially spiked inland in San Diego Creek, allowing water to approach Irvine’s 405 freeway.
And in the San Francisco Bay Area, near the tsunami, waves could surge four feet above average sea level at San Francisco’s Aquatic Park, Alcatraz Island, Redwood City and Richmond. Alameda 5 feet. 6 feet on Ocean Beach in San Francisco. 7 feet of Sausalit. 8 feet in Pacifica, San Mateo County. 9 feet in Bolina, Marin County, according to the California Geological Survey.
“Tsutami is a rare but real threat to our community,” said Reginald Harrison, director of disaster preparedness and emergency communications for Long Beach.
“However, unlike earthquakes, tsunamis provide natural warnings before they arrive,” Harrison said in a statement released ahead of Tsunami preparation week. “If you’re close to the beach when this happens, you need to move to the high altitudes as soon as possible.”
California has many communities of communities that are very challenging to evacuate quickly.
A survey published in 2020 identified nine densely populated populations, particularly problematic locations. Includes Naples Island in Long Beach. Oxnard Shores and South Channel Islands Beach in Ventura County. The island of Huntington Port. Balboa Peninsula/Lido Isle; Mission Beach Peninsula in San Diego. Bay Farm Island in Alameda, Coronado Peninsula.
Alameda is particularly vulnerable to tsunamis. Over 75,000 residents live in designated hazard zones, with few exits from the community. This is divided between Bay Farm Island (actually a peninsula) and Main Alameda Island.
However, officials there claim that “local mistakes have minimal risk of a significant tsunami.” Instead, they say the biggest risk comes from faraway areas and could create a tsunami 18 feet above sea level in Alameda.
Elsewhere, however, almost coastal tsunamis can produce the best waves. In Redondo Beach, for example, a near-coastal tsunami can cause waves up to 11 feet above average sea level, compared to the 9 feet chance of a distant earthquake.
Katie Eyin, Emergency Services Coordinator in Newport Beach, estimates that 45,000 people live in potential flood zones in the local flood zones around half the city’s entirety. However, she realized that there could be more visitors and workers, especially during the tourist season.
Ein said the near-coastal tsunami could be devastating. The city’s Hazard Mitigation Plan cites a study from USC that estimates that “potential potential landslides along sequestration off the steep coast of Southern California could create a tsunami.”
“The concern about these local tsunami sources is that travel time between the local source of the earthquake and the arrival of the first wave along the coastline is estimated to be 10-20 minutes, so warning and evacuation broadcasts don’t take much time,” the report said. “Some wave emblems are likely, with the second and third waves likely higher than the first.”
In comparison, Eing estimated that evacuating all areas of the flood zone would take several hours. That timeline was backed up by a 2015 investigation, and concluded that a complete evacuation of the area that is blocked by the Newport Beach tsunami will take nearly five hours.
Depending on the scenario, Eing said authorities may recommend evacuating some people to locations rather than causing sub-sea evacuation traffic.
“If it was a local earthquake… it would probably be safer. [residents] “To go to the third story,” she said.
The disruption and potential disruption in evacuation was far too adjacent when a magnitude 7 earthquake struck a crash about 30 miles from the Humboldt County coast last December.
A few minutes later I received a huge tsunami warning. It issued warnings to Californian mobile phones from the north coast through the San Francisco Gulf region, including Oakland, Berkeley and Alameda.
Luckily, only a small tsunami has been embodied in Mendocino County, just two inches tall. However, the reaction and reactions indicate that there is plenty of room for improvement.
Some of the people who chose to evacuate did not do so quickly, and there was extensive confusion, whether or not evacuation was necessary at all.
“Many people questioned how the tsunami could enter the bay and said it must be just coastal people who need to be evacuated,” one person told Berkeley in a survey. “There was a lot of confusion here and there, a lot of self-complaint and I didn’t take it seriously.”
Another complained that the only warning they got was the broad “emergency warnings” sent to all mobile phones as they were not signed up for Berkeley’s alert system. As a result, the person wrote, “there was no information about who should evacuate, who shouldn’t, access to the map, or how much time he had.”
Hesitancy is fatal. The 2011 magnitude 99.1 earthquake struck near Japan, rising high within just 30 minutes, creating a tsunami that reached the coast.
More than 18,000 people have died in the disaster, exacerbating tolls, which were exacerbated by the initial warnings that underestimated the size of the tsunami before the communications system was completely reduced. Another issue documented by seismologist Lucy Jones in his book The Big Ones was that some people would not be reluctant to evacuate.
As found in the Berkeley investigation, the unwillingness could be driven by a timely lack of information. For example, the California Tsunami Hazard Map website did not function during the alert period.
In response, San Mateo County, just south of San Francisco, has built its own online tsunami dashboard that allows residents and visitors to connect the locations to see if they are in the hazard zone and search for safe locations nearby.
Last December, Highway 1 was stuck with a driver trying to escape from Pacifica. What many didn’t realize is that in some vulnerable areas, a few blocks of inland is enough to safely get out of reach of the tsunami.
Some evacuees also headed in the wrong direction and headed from the highlands to lower areas in an attempt to escape.
San Mateo County Emergency Management Director Shruti Dapodkar heard from someone who lives in the coastal community of Montara. However, the resident fled directly to the lowlands on Highway 1.
“I want to make this point very clear… I want to move to highlands avoiding lowland areas” was objective and “not necessarily coming up on the hills in your car,” Dapodkar said.
It is important to understand which areas of the city are threatened by the tsunami – as if you know where there are safe areas. If you are on the Santa Monica pier, head over to the bluff about 100 feet above sea level. There is no need to run to Mount Bardi.
In many parts of San Francisco, heading just a few blocks away from the coast is enough.
The general advice is to evacuate by foot or bicycle, if possible, to avoid traffic jams. But some officials acknowledge that it could be a tough question across California cars.
The scenario may vary for a more distant tsunami that may take longer to evacuate.
“For most of LA, the majority of our evacuation zones are really beaches, a few blocks inland,” said Jennifer Razo, chief of the city’s emergency management department of innovation and technology.
But there are many areas where people may need to drive. In a remote source tsunami scenario, firefighters and police officers will be sent to oversee people, Razo said.
Additional important plans are being worked on. San Francisco says it needs to establish an evacuation strategy for people with disabilities, which is expected to be completed by 2027.
“In areas where highlands are not readily available, evacuation perpendicular to high-rise buildings and seeking evacuation may be the best option for life safety, especially for people with disabilities, access and functional needs,” the city’s danger plan states.
San Francisco also needs to develop and install signs on sidewalks and roads in low-lying waterfront areas to help people know where to go in the event of other coastal flood risks, such as the tsunami or Kingtize.
Some coastal regions have installed tsunami warning signs, but they are not ubiquitous.
“There’s a lack of signs throughout the state. Marine County – I’m going to talk to us – we definitely have limited signs across the county identifying tsunami flood zones,” said Stephen Torrence, Marine County’s director of emergency management. The County Board of Supervisors has no jurisdiction anywhere, he noted, but “we need to make sure that jurisdictions clearly identify these flood zones.”
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