Located on the west coast of the United States, California is the third-largest state in the country, stretching from the bottom of Oregon to the border of Mexico and covering cliff-lined beaches, redwood forest, and the Sierra Nevada Mountains. California is as typographically diverse as it is vast, but with nearly 900 miles of coastline, you might be wondering, are there any tsunami danger zones in California?
Natural disasters might not be the first things that come to mind when you conjure images of California’s rolling valleys, dramatic coastal roads, and glitzy beach communities from Malibu to Beverly Hills. However, California is a hotbed for tectonic activity and actually sits in the Pacific Ring of Fire, meaning that it’s no stranger to geohazards.
Our guide takes a look at the tsunami dangers zones in California, examining the possibility of a freak wave hitting the shores of the Golden State. We’ll also look at what you can do to stay safe in the event of a tsunami. Let’s get into it.
Could a tsunami happen in California?
Tsunamis are the stuff of nightmares and disaster movies, but they’re a very real phenomenon and feared by coastal communities all around the world. Tsunami means “harbor waves” in Japanese but these high seas aren’t as commonplace as their translation might have you believe.
Unlike normal ocean waves which are mostly caused by wind, tsunamis are the result of the displacement of large volumes of water. Under the sea earthquakes that move the earth’s outer layer or crust and force waves out in all directions from their source are usually the culprit for most tsunamis, but landslides and volcanic eruptions can also be to blame, displacing large walls of water that surge onto land and cause widespread damage.
Truth be told, minor under-the-sea tremors happen all the time and many don’t cause tsunamis, while others trigger small outputs of energy that result in slightly higher seas but limited impact on land. However, tragic tsunami events happen every year all around the world and they can have devastating impacts on coastal communities and even inland settlements.
The Pacific Basin, where Australasia joins South Asia, sees the most tectonic activity, thanks to the Pacific Ring of Fire, and around two destructive tsunamis take place annually in this region. Pacific-wide tsunamis (those which start in the Ring of Fire but are so forceful that they have impacts beyond the continent) occur every 10 to 12 years on average.
The Pacific Ring of Fire is a huge arc of mountains, active volcanoes, and oceanic trenches that stretches from New Zealand to eastern Asia, Papa New Guinea, Japan, and Alaska, as well as down the western coast of North America to Guatemala, Peru, and Chile. California is included in this ring and suffers a heightened risk of imminent earthquakes.
In fact, scientists say that there is more than a 95 percent chance of a magnitude 6.7 or great earthquake striking Northern California before the year 2030 with the San Andreas Fault running for 750 miles through the state. However, the San Andreas fault is a primarily continental tectonic boundary, meaning under the sea earthquakes right off California’s coast are less likely.
The transform fault, which is one of the most active in the world, does pass seaward into the Pacific Ocean in the vicinity of San Francisco. However, it cannot create a big tsunami as not enough of the fault is underwater. Earthquakes need to move the ocean floor in order to trigger a tsunami. A San Andreas earthquake could trigger landslides that displace water and produce large waves, but they wouldn’t be significant enough to cause widespread damage.
Still, this doesn’t mean California isn’t at risk of tsunamis.
Where are the tsunami dangers zones in California?
Recent findings issued by the California Governor’s Office of Emergency Services, which published an updated tsunami hazard map for seven of the nineteen coastal counties in the state, suggest that the entirety of California’s coastline is vulnerable to a tsunami. Despite the lively San Andreas fault, the biggest threat is not local. Rather, tectonic activity in the South Pacific and off the coast of Alaska poses more of a risk to California’s coastline.
The map shows that the strip of shoreline reaching from the Oregon Border in the north down to San Diego and Mexico’s Tijuana in the south could be struck by a tsunami, with a medium risk level issued for the whole coast. The most changes to the information last published in 2009 are in the Bay Area of San Francisco which faces new risks where warnings were previously isolated to outside of the harbor. However, the risk of a tsunami is still fairly evenly distributed throughout the state.
Even though all of the coastlines are vulnerable, nowhere in California faces a high-level risk of a tsunami, but evacuations would be likely if a large-level warning came from an event in the South Pacific or Alaska.
Tsunami danger zones in California with a medium risk alert include all of the coastal counties, namely Alameda, Contra Costa, Del Norte, Humboldt, Los Angeles, Marin, Mendocino, Monterey, Orange, San Diego, San Francisco, San Luis Obispo, San Mateo, Santa Barbara, Santa Clara, Santa Cruz, Solano, Sonoma, and Ventura.
If you live in any of these states or plan on visiting, it would be a good idea to familiarize yourself with the local tsunami evacuation protocol as a precaution.
What is the likelihood of a tsunami in California?
California is actually hit by around one tsunami a year, but we’re not talking about the mega-waves that engulf whole cities that you’ve seen on the big screen. Most of these tsunamis are barely noticeable and manifest as slightly higher waves that California’s shores are built to deal with. That said, the whole coastline of the state is vulnerable to a tsunami at any given time, so just how likely is it that one will do serious damage?
First, let’s look at the history of devastating tsunamis in California to determine the potential impact that one could have, and when.
The last tsunami to hit California was in January 2022, following the Hunga Tonga-Hunga Ha’apai eruption, an underwater volcano in the Tongan archipelago in the southern Pacific Ocean. The eruption started on 20 December 2021, and on 18 January 2022, waves of up to 15 m (49 ft) struck the west coasts of Tongatapu, Eua, and Ha’apai Islands.
A 20 m (66 ft) tsunami also struck Nomuka, the smaller island with a population of just 200, located 65 km northeast of Tonga.
The effects of this eruption were felt far and wide, and while the sonic boom of the volcano was heard as far as New Zealand, two-foot waves were also sent barrelling toward California’s Bay Area more than 8,000 km away.
A number of beaches and harbors in northern and central California suffered moderate flooding as a result, with Ventura and Santa Cruz experiencing significant damage following the high tides. This level of event is unusual, but distant earthquakes are the main trigger for tsunamis in California.
Since 1880, 150 tsunamis have struck California’s coast, most of which have been a result of earthquakes. Notable events were observed in 1700, 1812, 1946, 1964, and 2011, the worst on record being the 1964 event which was generated by a whopping 9.2 magnitude quake off the coast of Alaska.
Powerful waves slammed coastal areas of California, killing 11 people in North California’s Crescent City community. A 20 ft high surge flooded 30 city blocks and a total of 100 people along the west coast of the US, including Alaska, lost their lives.
The 2011 Tohoku earthquake and tsunami caused even more damage worldwide with its magnitude 9.1 undersea megathrust. More than 15,500 people died and the infrastructure of Japan was crippled. Less destruction took place in California than that from the 1964 event, but strong currents damaged harbors along California’s coast, with the worst damage reported in Crescent City again as well as Santa Cruz.
Despite the active South Pacific and its earthquakes and eruptions that have triggered some of the world’s most devastating tsunamis, Alaska’s Aleutian islands pose one of the biggest threats to California’s cast. The islands are volcanic in origin and were formed from the subduction of the Pacific plate beneath North America. They make up the northern arc of the Ring of Fire before it sweeps along Russia’s Kamchatka Peninsula and through Japan.
In the California Governor’s Office of Emergency Services’ recent publications, some new predictions include the potential of 18 to 25-foot swells that an earthquake off the Aleutian Islands could bring to the Santa Cruz Boardwalk. These heights are twice that predicted in the 2009 report.
Earthquakes in the Aleutian Islands aren’t uncommon, but severe ones are rare. Scientists say there is a nine percent chance of a magnitude 9 or higher earthquake striking the islands in the next 50 years, in which case, destructive tsunami waves could have a lethal effect on California’s coast.
Only four locally-generated tsunamis have ever been observed in California, with the most significant occurring in 1812 in Santa Barbara and Ventura County. Waves up to 10 feet high were reported while ships and buildings suffered bad damage.
What should you do in the event of a tsunami?
In the unlikely, but not unheard of, event that a tsunami was to hit California’s coast, it’s a good idea to know how to respond. Tsunamis can cause a lot of destruction and they’re hard to predict. Earthquakes also have nearly no advance warning, unless they’re caused by a large volcanic eruption, which can still be difficult to foresee.
The West Coast/Alaska Tsunami Warning Center (WC/ATWC) is responsible for warning Alaska, British Columbia, Washington, Oregon, and California in the case of potential tsunamis. These warning systems are most effective when the source of the tsunami, namely an undersea earthquake or volcanic eruption, is more than 1,000 miles away, such as in Japan or Chile, as they have more time to prepare.
In these cases, they can issue warnings with at least 90 minutes’ notice—but much longer in normal instances, before an event takes place. Underwater seismic activity is monitored 24/7 and the WC/ATWC works in conjunction with the Pacific Tsunami Warning Center in Honolulu, Hawaii, to keep updated on any changes registered on this side of the Pacific.
The WC/ATWC will intercept regular television and radio channels if necessary to alert citizens of an incoming tsunami and you shouldn’t take any action before such warnings have been issued. However, there are some signs from mother nature that you can look out for if a tsunami is hurtling at an unprecedented speed towards California’s shores, or if you live off-grid without access to regular programming:
- A severe earthquake – You might not be familiar with what an earthquake feels like if you’ve never experienced one. On the other hand, you might feel tremors all the time and nothing can ever come of them. But if you live near the coast and feel severe ground shaking that lasts for more than ten seconds, this might trigger a tsunami.
- Receding shoreline – Similar to how the tide draws back before a big wave crashes, an incoming tsunami can cause an abnormally receded shoreline, sometimes even exposing fishing nets, coral, and reefs. This could be an indication that a tsunami is on its way and retreating from the beachfront is a good idea.
- Roaring ocean – There’s a high chance you’ll hear a tsunami before you see it, especially at night or if you’re inside. The sound of the approaching wave has been likened to a train or jet aircraft and is known as an “ocean roar”. If you hear this, get high up as soon as you can.
With more than 26 million people living in coastal portions of the state of California, that’s more than 75 percent of the total population, it is important that residents are familiar with their local tsunami and evacuation protocol.
You can find these regulations on the California Government site in the Tsunami Preparedness Handout. Here are some extra things you can do to keep safe:
- Don’t panic – If a tsunami warning has been issued, it still doesn’t mean that freak waves are guaranteed. Don’t panic and listen to official instructions before you take any irrational measures.
- Know your evacuation routes – Tsunami warnings might be precautionary a lot of the time, but if you live very near the coast, familiarizing yourself with your evacuation routes isn’t a bad idea.
- Stay away from the beach – This sounds like an obvious one, but you’d be surprised how many people head straight for the shores in the event of a tsunami warning, needing to see it before they can believe it. Stay away from the beach and get to higher ground.
- Respond to earthquakes – If a tsunami warning has been issued and it’s followed by another big tremor, it might be a good idea to start taking action. Once it’s safe to do so, evacuate the tsunami hazard zone, if you’re in one, following an earthquake.
- Get high – If there isn’t time to follow state-planned evacuation and a tsunami is imminent, get as far inland as you can and high up. Two miles is a safe distance from shore to be in the event of a tsunami. If you don’t have time, aim for 100 feet above sea level and choose a sturdy building with strong foundations.
