These California coastal cities face heightened flood danger from tsunami, data show
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. 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.
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.
'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.
Read more: Are you at risk of tsunami flooding in Southern California? Check these maps
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.
And with the state's annual tsunami preparedness week set to start Saturday, officials say it's vital for residents to familiarize themselves with their local risks.
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.
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.
Read more: Where in Northern California is most at risk for tsunami flooding? Check these maps
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.
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.
"These are both areas with very low land elevations that could be impacted by a small increase in waterfront flooding," the geological survey said.
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.'
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.
And, as the maps show, it's not always areas right along the coast that are exposed. Tsunami hazard zones can extend to bayside and riverside areas relatively far from the Pacific coast, representing the maximum inundation area in a number of scenarios, according to the California Geological Survey.
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. Some of the most storied sections of San Francisco — including parts of the Financial District as well as the Ferry Building, Fisherman's Wharf, the Palace of Fine Arts, Chase Center, Oracle Park and Treasure Island — could see flooding from a major tsunami.
The same is true for much of Alameda; sizable chunks of Oakland, Berkeley, Richmond and Marin County; and some areas in and near Silicon Valley, including northern sections of Redwood City and Burlingame.
To the south, some coastal communities along Highway 1 in San Mateo County are in a tsunami hazard zone — such as parts of Pacifica and Half Moon Bay — as are other popular tourist destinations in counties farther south, like Capitola and Monterey.
The risk extends north too. Humboldt and Del Norte counties have significant tsunami risk. There are vast areas around Eureka, next to Humboldt Bay, where there are long, skinny peninsulas that could make an evacuation challenging.
Read more: 'Living here isn't easy to begin with.' How an earthquake brought people together
In Ventura County, parts of Ventura, Oxnard and Port Hueneme are in the tsunami hazard area, including the neighborhoods of Oxnard Shores and Ventura Keys, as well as the Ventura Marina Mobile Home Park.
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.
There was, technically, a tsunami — albeit one measured at a scant 5 centimeters — in Arena Cove off Mendocino County.
Read more: 'It's insane.' How rattled Northern Californians weathered 7.0 earthquake and tsunami warning
A nightmare scenario for California would be a tsunami generated from an underwater quake that occurs close to shore. A particularly chilling prospect for Northern California, as well as Oregon and Washington, would be a magnitude 9 earthquake along the Cascadia subduction zone off the coast.
A major quake in this area could bring a tsunami to San Francisco in as little as an hour. An even closer rupture, such as along the Point Reyes thrust fault, could result in a tsunami hitting the city in as little as 10 minutes, according to city documents.
'You just experienced a significant alert — one that may never happen again to you,' Snider said. 'But in the event that it does … ask yourselves, did I have alerts when I needed them?'
It's important to remember that tsunamis are not like typical ocean waves. They are series of waves that reach shore almost like a turbulent wall of water or a fast-rising flood.
Read more: The California tsunami danger is real. The 7.0 earthquake is wake-up call to prepare
Perhaps nowhere in California better demonstrates the risk tsunamis present than Crescent City. Most notably, the 1964 Alaska earthquake set off a catastrophic tsunami that devastated the city, washing away 29 blocks and killing at least 11 people. Surges reached 21 feet above the average low tide.
A hypothetical magnitude-9.3 earthquake near Alaska's eastern Aleutian Islands could bring a damaging tsunami to the San Francisco Bay Area in about five hours, and to L.A. and Orange counties in about six.
If you're uphill or inland from the mapped hazard zones, you should be safe from tsunami. But those who live, work or recreate in a hazard zone should have an evacuation plan, especially since authorities may only have minutes to decide whether to order everyone to higher ground.
If you don't have prior knowledge of whether you're in a tsunami hazard zone, and no maps or evacuation signs are available, aim for spots 100 feet above sea level and as far as two miles away from the shoreline, if possible, officials say.
Read more: Why a massive California tsunami alert was issued — then soon canceled
Officials say it's also important to know if you're not in a tsunami hazard zone, to avoid complicating evacuations for those who need to move. There's no need, for instance, to flee San Francisco when much of the city is in a safe zone — just walking a few blocks inland may be all that's needed.
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.
And evacuating the Santa Monica Pier doesn't mean you need to head to the top of Mt. Baldy. Just getting above the nearby bluffs would be enough.
But even where tsunami hazard zones are relatively narrow, many Californians may not have the instinct to get to higher ground after the ground shakes.
And the risk can vary. The tsunami hazard area in Manhattan Beach is essentially limited to the beach and pier on the coastal side of the Strand, the walking-and-biking path that separates the sand from luxury homes. Yet in Hermosa Beach, the latest expanded tsunami hazard area also now covers the pricey homes a block or so east of the trail.
Visiting SeaWorld in San Diego? The theme park is outside the hazard zone, but some hotels and resorts to the west and north are not.
Those who were ordered to leave during the widespread warning in December should assess whether their evacuation plan worked and if there is anything that needs to be tweaked or ironed out, Snider said.
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This story originally appeared in Los Angeles Times.
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USA Today
6 days ago
- USA Today
A fog-free San Francisco? Scientists ponder California's climate future
A fog-free San Francisco? Scientists ponder California's climate future Nearly 70% of Californians live in coastal counties, which figure to be most impacted by diminished fog. Show Caption Hide Caption Climate change is now impacting where Americans choose to live Many U.S. locales have reached a climate change "tipping point." Populations are declining as flooding becomes unbearable. SAN FRANCISCO – As most of the U.S. sweltered in mid-July 2022 − when temperatures in many major cities reached the high 90s and even triple digits − a national weather map showed San Francisco topping out at 65 degrees. It was just a typical foggy summer day in the city by the bay, which averaged 62 degrees that month, about the same as the next two Julys. Now the advent of climate change raises the question of whether summertime visitors will stop rushing out to buy sweatshirts upon arrival and instead feel perfectly comfortable in shorts and T-shirts. The future of San Francisco's iconic fog has been debated in media stories during recent years, and some experts note a diminished cloud cover along the California coast that could lead to a warming trend. But few if any detect signs that San Francisco's summer chill is going away like the once-celebrated Fog City Diner, which shut down at the end of May. 'From the data, I can't foresee it any time soon,'' said Rachel Clemesha, a project scientist with the Scripps Institution of Oceanography at the University of California-San Diego who studies the state's coastal climate. 'There are years when there's more or less cloud cover. The last couple of years have been within that range. It is a very foggy place, so it would be very dramatic to get you a fog-free city.'' Data on decreasing fog along coast is 'spotty' Clemesha said some decrease has been confirmed in Southern California in what residents there call the marine layer, mostly in highly urbanized areas, but nothing that applies statewide. Peter Weiss, a faculty researcher and lecturer at the UC-Santa Cruz department of environmental sciences, said that despite a growing narrative of waning fog along the California coast, the data to support it is 'very spotty,'' with few academic studies in the last decade. The reasons include the fog's unpredictability – Weiss calls it an 'ephemeral phenomenon'' – and the lack of a standard way to measure it. Some studies, such as the landmark analysis by James Johnstone and Todd Dawson in 2010, rely on airport visibility records. Others use satellite images to determine the extent of the cloud cover, and others yet believe water content is a more valuable gauge. The airport records are the most extensive, going back to 1950, and Weiss said from that year until 2012 they revealed a 5% decrease in fogginess. 'Nobody's quite sure why,'' he said. 'It probably has to do with the ocean's sea-surface temperature, and that goes through various phases. Overall, there's warming due to global warming, but it's episodic. There appears to be some pattern with less fog after the warmer sea-surface temperatures, but this is still an area of research.'' Many California residents, ecosystems would be affected While the scientific community endeavors to figure out the long-range impact of climate change on California's coastal fog, there's a strong consensus that diminished cloud cover would have a harmful effect. Nearly 27 million of California's 39 million residents – close to 70% – live in coastal counties, by far the largest total in the nation, and they generate 80% of the state's gross domestic product. Their lives are certain to be impacted, as would be the state's powerhouse agriculture industry, which totals close to $60 billion a year in revenue. Species such as the widely admired coastal redwoods, which get up to 40% of their yearly water intake from fog, could be threatened if that resource dwindled. Daniel Fernandez, an environmental sciences professor at Cal State Monterey Bay, is part of a group seeking a grant from a private foundation to study how climate change may alter fog and affect various ecosystems. 'You could have significant die-off of species that are dependent on the fog at locations where it gets reduced,'' he said. 'It would also change how people live. When you look a fog zones, you don't need air conditioning. There are a lot of things we don't need that we take for granted. Those things could all change.'' It can feel like living in a cloud The fog, more prevalent in the summer, is created when warm and moist air sweeps over cold waters, which are churned off the California coast by strong winds in what's known as upwelling. The marine cover can be light enough to simply cool down a warm day and thick enough to wet residents' hair and obscure their eyeglasses, giving the impression they're living in a cloud. Some years the fog is thicker than others, but it tends to be more extensive in Northern California than the state's southern coast because of the differences in their ocean temperature (colder in the north), latitude and topography. Ian Faloona, a professor of land, air and water resources at UC Davis, said he and a colleague conducted a study using regional climate models and found a downward trend in cloudiness along the coast, but agrees the overall evidence 'is not going to hit you over the head.'' He compares that to the abundant data indicating California in general is warming quickly, about 1 degree Celsius – 1.8 degrees Fahrenheit – per decade. Even San Francisco is heating up a bit, though not nearly as fast: Its average summer temperature has risen by 1.6 degrees Fahrenheit since 1970, according to the independent research group Climate Central. Two different perspectives on what the future holds But climate scientists are split over whether the increased heat will lead to less fog because the air over the ocean won't be cold enough to condense, or whether stronger winds will atone for that factor. 'Under climate change, we know the land is warming much faster than the ocean, so that temperature difference across the land and ocean interface is increasing, which could drive stronger winds, which could help preserve this cloudiness,'' Faloona said. 'So there are two arguments you could make about what we theoretically think should happen, and which one's winning out I think is still an open scientific question.'' Sara Baguskas, an assistant professor at San Francisco State University with a specialty in coastal fog, said the lack of conclusive evidence that it's ebbing should not induce complacency but rather stimulate funding to study and predict its patterns. She's among the climate researchers who have heard from longtime coastal residents saying the marine layer has subsided over the years. 'So it's not unreasonable to be concerned about coastal fog declining in the future, but it diminishing completely is unlikely,'' she said. 'No coastal fog in California is a scary thought for both people and ecosystems.''
Yahoo
08-06-2025
- Yahoo
California tsunami: Here's where damage and casualties could be the worst
Tsunamis pose a risk to the entire California coast. But should a major one strike, how bad could it be? A single tsunami likely won't cause the worst-case scenario for every region. But in total, more than 680,000 Californians are in a tsunami hazard area during the daytime. And in all, $12.6 billion in damage is possible across California's 20 coastal and bayside counties — a figure that doesn't include damage to ports, harbors, roads, essential facilities or other infrastructure. There are two main types of scenarios for a tsunami. The first, a "distant-source" tsunami, comes from far away, like one spawned by a major earthquake in Alaska. That would provide an extensive warning — six hours for L.A. and five hours for San Francisco — but could produce the highest level of inundation for large swaths of the state. Then there are "near-source" tsunamis, which can wash ashore in as little as 10 minutes following a nearby earthquake — leaving little time for a notice or evacuation. Here are some scenarios for different parts of California. Unless otherwise mentioned, figures are from the California Tsunami Program, which is run by the California Governor's Office of Emergency Services and the California Geological Survey. Read more: These California coastal cities face heightened flood danger from tsunami, data show Distant-source tsunami: More than 350 people could die or be injured along the Southern California coast if people wait to evacuate half an hour after an official evacuation warning is given. That includes about 200 casualties in Los Angeles County, roughly 80 in San Diego County, 60 in Orange County and about a dozen in Ventura County. A hypothetical magnitude 9.3 earthquake from Alaska — similar in scale to the monstrous 1964 tsunami-generating temblor — would offer six hours of warning; large temblors from Chile could provide 13 hours of warning. The maximum projected distant-source tsunami could bring waves of 15 feet above the mean sea level to Marina del Rey, the Santa Monica Pier, Naples and Alamitos Bay; 14 feet elsewhere in other parts of Long Beach; 10 feet at Manhattan Beach, San Pedro and the ports of Los Angeles and Long Beach; 9 feet in Malibu, Redondo Beach and Palos Verdes Hills; and 8 feet at Leo Carrillo State Beach. Those estimates were issued by the California Geological Survey and published in the city of Los Angeles' hazard mitigation plan. Damage estimate from distant-source tsunami: More than $1.4 billion. Near-source tsunami: Los Angeles could see a tsunami move from its source to coastal areas in as few as 10 or 15 minutes, the city's tsunami plan warns. According to public documents, depending on the fault that ruptures, or where an underwater landslide is triggered, there could be locally generated tsunami heights of 30 feet in Avalon on Catalina Island; 24 feet at Palos Verdes Hills; 18 feet in Two Harbors; 11 feet in Redondo Beach; 9 feet in Malibu; 8 feet in Long Beach and the Santa Monica Pier; 7 feet in Manhattan Beach and San Pedro; 5 feet in Marina del Rey; and 4 feet at Leo Carrillo State Beach. In the city of Los Angeles, officials say that the most catastrophic scenario would involve an underwater landslide triggered by an earthquake, because "we wouldn't know that that landslide would occur until the wave arrives," said Jon Brown, assistant general manager for the city's Emergency Management Department. Other L.A. County areas with considerable vulnerability include the ports, as well as San Pedro and Long Beach. The city of Los Angeles has an estimated 23,000 residents in the tsunami hazard area. In Long Beach, the number is 31,000. Read more: The tsunami that battered Santa Cruz highlights the threat facing California's coast Distant-source tsunami: More than 230 people could die or be injured if people wait half an hour to evacuate after an official warning is given. Santa Cruz County could see more than 130 casualties; San Luis Obispo County, about 80. The estimated potential casualty tolls could be 16 in Monterey County and seven in Santa Barbara County. Damage estimate from distant-source tsunami: More than $3.5 billion. Near-source tsunami: Santa Cruz and Monterey counties could see a tsunami within minutes following quake-triggered underwater landslides, documents from both counties say. "Even a moderate earthquake could cause a local-source tsunami from submarine landsliding in Monterey Bay," public documents say. A near-source tsunami could bring waves of up to 15 feet above the mean sea level in the city of Marina, 9 feet at the Salinas River; 8 feet at the Pajaro River and Sand City, just northeast of Monterey, and 6 feet at Moss Landing, according to data published in Monterey County's hazard mitigation plan. Such devastation would not be unprecedented. A large earthquake in the Santa Barbara area in 1812 resulted in a tsunami "that wiped out many coastal villages and destroyed ships in the harbor," according to the U.S. Geological Survey. And 7-foot waves resulted from a tsunami in 1927, generated by an earthquake about 5 miles west of the Santa Barbara County coast, according to the California Geological Survey. The USGS said there's evidence of deposits from underwater landslides offshore of Santa Barbara dating back over 160,000 years, which suggests that "future earthquakes could cause large submarine landslides and devastating tsunamis." Read more: Can a tsunami happen in Southern California? What should you do about it? Distant-source tsunami: More than 1,300 people could die or be injured if people wait half an hour to evacuate after an official warning is given. About 500 of them could be in San Francisco; about 300 apiece in San Mateo and Marin counties; nearly 200 in Alameda County and 33 in Contra Costa County. Just north of the region, in Mendocino County, five people could die or be injured in that scenario. A hypothetical tsunami-generating earthquake in Alaska could provide 5 hours of warning; one from Chile could provide 13 hours of warning. The maximum projected distant-source tsunami could result in tsunami of 32 feet above mean sea level in San Francisco's Ocean Beach; 31 feet in Pacifica in San Mateo County; 27 feet in Bolinas in Marin County; 18 feet in Alameda; 14 feet in Sausalito and San Francisco's Aquatic Park; 13 feet on Alcatraz Island; and 11 feet in Richmond and Treasure Island, according to the California Geological Survey. Damage estimate from distant-source tsunami: More than $6.5 billion. Near-source tsunami: In Northern California, a near-source tsunami could generate a tsunami of 9 feet above sea level in Bolinas; 8 feet in Pacifica; 7 feet in Sausalito; 6 feet at Ocean Beach; 5 feet in Alameda; and 4 feet at Alcatraz Island, Treasure Island, Aquatic Park, Redwood City and Richmond. Read more: The California tsunami danger is real. The 7.0 earthquake is wake-up call to prepare Cascadia scenario: Given its proximity to the Cascadia subduction zone, Del Norte County — the state's northernmost coastal region — is perhaps more exposed to tsunami risk than any other part of California. If people wait 10 minutes after an earthquake to evacuate — the shaking itself would be the warning to flee — more than 3,150 are at risk of being killed or injured by tsunami in Del Norte County, and more than 720 would be at risk in neighboring Humboldt County. 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. "A large quake generated by the Cascadia subduction zone could create waves twice as large as the 1964 event, especially in Crescent City," Rick Wilson, a former head of the California Geological Survey tsunami program, said in a statement. Damage estimates: Del Norte County, which is home to Crescent City, could see more than $1 billion in damage. Humboldt County, home to Eureka, could see $22 million. Sign up for Essential California for news, features and recommendations from the L.A. Times and beyond in your inbox six days a week. This story originally appeared in Los Angeles Times.
Los Angeles Times
08-06-2025
- Los Angeles Times
An earthquake just off California's coast poses dire tsunami risk for many communities
SAN FRANCISCO — California does not often experience dangerous tsunamis, but there is one type of ocean surge some experts are increasingly concerned about. Near-shore tsunamis — those triggered by earthquakes just offshore — could pose a particularly dire risk for California's heavily populated coastal communities, according to experts, disaster modeling and local hazard plans. Depending on the strength and location of the quake, life-threatening waves could approach the coastline in as few as 10 minutes, perhaps not even enough time for an emergency alert to be issued, much less arrive on your cellphone. And it's a potential threat all along California's 840-mile coast, from the dense cities in the south to more remote reaches in the north. Data published in both the city and county of Los Angeles' hazard mitigation plans show how locally generated tsunamis could reach heights of up to 5 feet above the mean sea level in Marina del Rey; 7 feet in Manhattan Beach and San Pedro; 8 feet in Long Beach and the Santa Monica Pier; 9 feet in Malibu; and 30 feet on Catalina Island — depending on the fault that ruptures or where an underwater landslide is triggered. In Orange County, a magnitude 6.8 quake just offshore could bring a local-source tsunami to the coast in as little as 15 minutes, county documents say. A quake-triggered submarine landslide could inundate areas in Newport Beach — including Balboa Island, Balboa Peninsula and Lido Isle — and potentially surge so far inland up San Diego Creek that water approaches the 405 Freeway in Irvine. And in the San Francisco Bay Area, near-shore tsunami could cause waves to surge 4 feet above mean sea level at San Francisco's Aquatic Park, Alcatraz Island, Redwood City and Richmond; 5 feet in Alameda; 6 feet at San Francisco's Ocean Beach; 7 feet in Sausalito; 8 feet in Pacifica in San Mateo County; and 9 feet in Bolinas in Marin County, according to the California Geological Survey. Reginald Harrison, director of disaster preparedness and emergency communications for the city of Long Beach, said 'tsunamis are a rare but real threat to our community.' 'Unlike earthquakes, however, tsunamis provide natural warnings before they arrive,' Harrison said in a statement released ahead of Tsunami Preparedness Week. 'If you are near the beach when this occurs, you should move to higher ground as quickly as possible.' California is home to a number of communities where evacuating quickly could be immensely challenging. A study published in 2020 identified nine densely populated and particularly problematic places. They include Naples island in Long Beach; Oxnard Shores and southern Channel Islands Beach in Ventura County; the islands in Huntington Harbour; Balboa Island; Balboa Peninsula/Lido Isle; San Diego's Mission Beach peninsula; the Coronado peninsula, and Bay Farm Island in Alameda. Alameda is particularly vulnerable to tsunami. More than half its about 75,000 residents live in a designated hazard zone, and there are few exits from the community — which is split between Bay Farm Island (actually a peninsula) and the main Alameda island. However, officials there contend 'there is minimal risk of any significant tsunami occurring' from a local fault. Instead, they say, the greatest risk is from distant areas, which could produce tsunami of as much as 18 feet above sea level in Alameda. In other places, though, a near-shore tsunami could produce the highest waves. In Redondo Beach, for instance, a near-shore tsunami could bring waves of up to 11 feet above mean sea level, compared to 9 feet possible coming from a distant earthquake. Katie Eing, the emergency services coordinator for Newport Beach, estimated 45,000 people live in the potential local inundation zone, about half of the entire city's population. However, she noted many more visitors and workers could also be present, especially during tourist season. Eing said a near-shore tsunami could be devastating. The city's hazard mitigation plan cites a study from USC that estimates 'a potential submarine landslide anywhere along the steep Southern California offshore escarpment could generate a tsunami' that reaches an elevation of 30 feet to 33 feet above sea level. 'The concern with these local tsunami sources is that travel time between the local source of an earthquake and the arrival of the first waves along the coastline is estimated at 10 to 20 minutes, which does not allow much time for broadcasting of warnings and evacuation,' the report said. 'Several wave crests are likely, with the second and third waves likely to be higher than the first.' Evacuating all areas of the inundation zone, by comparison, would take hours, Eing estimated. That timeline is backed up by a 2015 study, which concluded a full evacuation of Newport Beach's tsunami-vulnerable areas could take almost 5 hours. Depending on the scenario, Eing said officials may recommend some people shelter-in-place rather than chance getting stuck in evacuation traffic at or below sea level. 'If it was a local-sourced earthquake… it's probably safer for [residents] to go to the third story,' she said. 'It's important to know where you live, if you're in the inundation zone.' The potential for chaos and confusion in an evacuation became all-too-apparent last December, when a magnitude 7 earthquake struck about 30 miles off the Humboldt County coast. An expansive tsunami warning arrived minutes later — sending alarms blaring on the cellphones of Californians from the North Coast through the San Francisco Bay Area, including Oakland, Berkeley and Alameda. Fortunately, only a small tsunami ended up materializing, just 2 inches high in Mendocino County. But the response and reaction shows plenty of room for improvement. Some of those who chose to evacuate didn't do so promptly, and there was widespread confusion whether evacuation was necessary at all. 'Many people questioned how a tsunami could enter the Bay and stated it must only be people on the coast who need to evacuate,' one person told the city of Berkeley in a survey. 'There was just tons of confusion all around, lots of complacency and not taking it seriously.' Another person complained that the only warning they got was the broad 'emergency alert' sent to all cellphones, as they weren't signed up for Berkeley's alert systems. As a result, 'we had no information at all about who should evacuate and who should not, access to a map, how much time we had,' that person wrote. Hesitation can be deadly. The 2011 magnitude-9.1 earthquake that struck near Japan spawned a tsunami that rose as high as 45 feet and reached the coast within just 30 minutes. More than 18,000 people died in the disaster, a toll exacerbated by an initial warning that underestimated the size of the tsunami before communications systems cut out entirely. Another issue, as documented by seismologist Lucy Jones in her book 'The Big Ones,' was the reluctance of some people to evacuate. That reluctance, as the Berkeley survey found, could be fueled by a lack of timely information. California's tsunami hazard map website didn't work during the alert period, for instance. In response, San Mateo County, just south of San Francisco, built its own online tsunami dashboard that lets residents and visitors plug in their location to see if they're in a hazard zone, as well as search for nearby safe places. Last December, Highway 1 was clogged with motorists trying to flee Pacifica. What many didn't realize is that in some vulnerable areas, heading just a few blocks inland was enough to safely be out of a tsunami's reach. Some evacuees also went in the wrong direction, driving from higher ground into lower-lying areas in an attempt to flee. Shruti Dhapodkar, director of emergency management for San Mateo County, heard from someone who lives in the coastal community of Montara — which is high enough in elevation that no tsunami would be expected to ever hit it. Yet that resident fled on Highway 1, directly into a low-lying area. 'I want to make this point very, very clear ... avoiding low-lying areas and moving to higher ground' is the objective, 'not necessarily getting in your car and coming over the hill,' Dhapodkar said. Understanding what areas of a city are threatened by tsunami are crucial — as is knowing where the safe areas are. If you're at the Santa Monica Pier, just head up above the bluffs, which are at about 100 feet above sea level. You don't need to run to Mount Baldy. In many parts of San Francisco, heading a few blocks away from the coast is enough to get to safety. The general advice is to evacuate by foot or on bicycle if possible to avoid traffic jams. But some officials acknowledge that could be a tough ask in car-crazy California. For more distant tsunamis, where hours may be available for an evacuation, scenarios can vary. 'For most of L.A., a huge chunk of our evacuation zone really is the beach and a couple of blocks inland,' said Jennifer Lazo, division chief of the innovation and technology division at the city's Emergency Management Department. But there are a number of areas in which people may need to drive out. In distant-source tsunami scenarios, firefighters and police officers would be dispatched to direct people out, Lazo said. Additional, crucial planning remains in the works. San Francisco says it needs to establish an evacuation strategy for people with disabilities, which it plans to complete by 2027. 'In areas where high ground is not immediately available, vertically evacuating and seeking refuge in tall buildings might be the best option for life safety, especially for people with disabilities or access and functional needs,' the city's hazards plan says. San Francisco also needs to develop and install signs on sidewalks and streets in low-lying waterfront areas to help people know where to go in case of tsunami and other coastal flood hazards, such as king tides, the city says. Some coastal areas have installed tsunami warning signs, but they're not ubiquitous. 'There is a lack of signage just throughout the entire state. Marin County — I'll speak to us — we definitely have limited signage throughout the county identifying tsunami inundation zones,' said Steven Torrence, Marin County's director of emergency management. The county Board of Supervisors doesn't have jurisdiction everywhere, he noted, but 'we need to make sure that the jurisdictions are clearly identifying these inundation zones.'
