Introduction to Tsunami Risk in California
The risk of damaging flooding from a major tsunami may be greater than many realized along stretches of California’s renowned coastline, state officials say, further reinforcing the need for residents to take note if they live in or visit hazard areas. The most recent risk assessment, outlined in maps that were published by the California Geological Survey and reviewed by The Times, illustrate the devastation that could result from scenarios considered to be extreme, but realistic.
Understanding the Risk Assessment
For instance, a large tsunami could flood swaths of Marina del Rey, Long Beach and the nearby dual port complex to an elevation of up to 15 feet above sea level. A worst-case tsunami could bring flooding to sizable areas of Oakland, Berkeley and Alameda, up to 18 feet above sea level. Flooding could reach up to 30 feet above the average high tide along the outer coast of Humboldt Bay and the Eureka area, and up to 50 feet toward Crescent City and Cayucos.
Importance of Knowing Tsunami Hazard Zones
But for most Californians, the precise extent of tsunami risk is less important than knowing these hazard zones exist in the first place. The magnitude 7 quake Dec. 5 off the Humboldt County coast — which prompted a tsunami warning affecting millions in Northern California — was a blaring reminder of that. Should a significant tsunami materialize, mere minutes could be the difference. Along California’s North Coast, some people might only have 10 minutes to get to an evacuation area following a huge earthquake just offshore.
Preparing for Tsunami Risks
“While damaging tsunamis are infrequent in California, they have and do happen. If you live on or visit the coast, you need to be aware of this potential hazard,” Steve Bohlen, then the head of the California Geological Survey, said when the updated tsunami hazard area maps were released. To see if you live in a tsunami hazard zone, visit conservation.ca.gov/cgs/tsunami/maps. The latest maps were published between 2020 and 2022. Though shunted out of the spotlight by other news events during that period, they are nevertheless notable — containing several major updates from earlier tsunami inundation maps that were published a decade earlier or more.
Updates to Tsunami Hazard Areas
The updates to California’s tsunami hazard areas followed a devastating tsunami in Japan in 2011, which was triggered by a magnitude 9.1 earthquake off the country’s eastern shore. Prior to that disaster, Japan relied on data from several hundred years of records to estimate tsunami risk, which once “seemed perfectly reasonable,” according to Bohlen. But the disaster demonstrated the need for scientists to consider even rarer events — tsunamis that may only strike once every 1,000 years or so. California, as a result, opted to take “a very conservative approach” for its maps, “hoping to avoid the tragic loss of life experienced in Japan,” Bohlen said in a prior statement.
Scenarios for Tsunami Warnings
There are a number of scenarios in which California could get hours of lead time ahead of a damaging tsunami. But should a quake strike close to shore, there could be little to no warning, aside from the shaking itself. “The bottom line is, if you’re near the coast and feel strong shaking from a local earthquake or get an official notification to evacuate, move inland as soon as possible,” Rick Wilson, then a senior engineering geologist with the California Geological Survey tsunami unit, said in a statement in 2021.
Expanded Tsunami Flood Areas
In the latest update of the maps, potential tsunami flood areas were expanded in parts of Long Beach — including along Ocean Boulevard and Belmont Shore — Malibu, Santa Monica, Venice, Marina del Rey, Hermosa Beach, Redondo Beach and San Pedro. Areas of notable concern in Los Angeles County include Marina del Rey, the ports of Long Beach and Los Angeles, and around Alamitos Bay because there are few roads for evacuation, according to the California Geological Survey.
Notable Concerns and Updates
Flooding to the extent considered possible in an extreme scenario “would inundate almost all of the land in the ports and some of the surrounding communities,” Wilson said when the latest maps were released. In updating the maps, San Francisco also saw “significant increases in the mapped tsunami hazard” in the Financial District at the foot of Market Street, as well as parts of North Beach, south of the Embarcadero. The zone includes the Embarcadero BART and Muni stations and Embarcadero Center.
Variability in Hazard Zones
In many places, changes in the hazard maps were relatively modest. Some — like in Newport Beach — were expanded to add a small buffer beyond the modeled inundation area to roads or landmarks to help local officials communicate evacuation plans, the geological survey said. “There are places on the U.S. West Coast, and here in Alaska, where an entire safe evacuation for a near-shore event … would [have] a much lower success rate,” said Dave Snider, the tsunami warning coordinator at the National Tsunami Warning Center in Alaska. “That is the No. 1 reason why people need to understand what their hazard zone is ahead of time.”
Changes in Hazard Areas
The changes went both ways. Some areas, such as around Huntington Beach and Bolsa Chica, saw their tsunami hazard areas shrink after new analysis indicated levees and ponds would help better protect the public than originally thought. What became clear in the wake of December’s widespread warning was that many Californians had no idea where the tsunami warning zones were.
Extensive Tsunami Hazard Areas
California’s tsunami hazard areas are expansive in some areas, and include some of the state’s priciest real estate and most famed destinations: the Santa Monica Pier, Long Beach’s Naples Island, Newport Beach’s Balboa Island and Balboa Peninsula; and neighborhoods in Sunset Beach, Seal Beach, San Diego and nearby Coronado. Also at potential risk are popular tourist hotspots from Malibu to Santa Barbara’s waterfront, the Monterey Bay Aquarium and a swath of Santa Cruz.
Conclusion
Given the extent of the assessed hazard areas, large-scale evacuations could be ordered, and warranted, in situations with limited time and information. That was the case in December. Although that warning was later canceled, and no major tsunami developed, Snider said it’s still a good reminder that this kind of disaster can happen, and people need to be prepared. Understanding tsunami risks and having evacuation plans in place are crucial for the safety of Californians and visitors alike.
FAQs
- Q: How can I find out if I live in a tsunami hazard zone?
A: You can visit conservation.ca.gov/cgs/tsunami/maps to see if you live in a tsunami hazard zone. - Q: What should I do if I feel strong shaking from a local earthquake?
A: If you’re near the coast and feel strong shaking from a local earthquake, move inland as soon as possible. - Q: Can tsunamis affect areas far from the coast?
A: Yes, tsunami hazard zones can extend to bayside and riverside areas relatively far from the Pacific coast. - Q: How high can tsunami flooding reach?
A: Flooding can reach up to 15 feet above sea level in some areas like Marina del Rey and Long Beach, and even higher in other areas like Crescent City. - Q: What is the best course of action if evacuation is impossible?
A: If evacuation is impossible, your last resort could be going to the third or higher floor of a sturdy building, or even climbing a tree.
