Coastal Threats: Understanding Tsunami Risks Across U.S. Shores
How Earthquakes and Tsunamis Continue to Shape Preparedness on America’s Coastlines Buraopost Newsletter
Tsunami alerts are a familiar occurrence along the West Coast, where warning systems and signage in various areas offer a sobering reminder to coastal communities: a massive wave may be heading their way.
However, the truth is that tsunamis are not limited to one region. They have the potential to strike any part of the U.S. coastline, whether on the Pacific or Atlantic shores.
On Thursday, these warnings were activated when residents in Northern California received tsunami notifications shortly after a powerful 7.0 magnitude earthquake shook the area off the Humboldt County coastline at 10:44 a.m.
The alerts informed residents that a tsunami might begin impacting the coastline near Fort Bragg by 11:10 a.m. local time, traveling along the northern California and southern Oregon coasts, and potentially reaching San Francisco by 12:10 p.m. People within the designated area—from Davenport, California, near Santa Cruz, to the Douglas Lane County line in Oregon—were advised to leave beaches, move away from the water, and evacuate to safer locations beyond designated hazard zones.
Roads near the quake's epicenter became congested as people rushed to evacuate from low-lying coastal areas.
Tsunamis are triggered when an underwater seismic event causes the rapid displacement of vast amounts of water. This movement generates a series of massive waves that gain energy as they travel across the ocean, eventually reaching shorelines with devastating force, often penetrating far inland and causing widespread destruction.
The term “tsunami” originates from the Japanese phrase meaning “harbor wave.” These waves can be particularly catastrophic in bays and harbors, where the water is funneled and amplified, leading to even higher wave surges.
A historical example occurred in 1964, when a colossal 9.2 magnitude earthquake in Alaska created a tsunami that struck Crescent City, California, five hours later. The epicenter of the quake was over 1,600 miles away, yet the resulting waves surged to nearly 21 feet, claiming 11 lives and devastating 29 blocks of the city, according to local records.
In more recent memory, a tsunami warning was issued for the San Francisco Bay Area in March 2011 following a 9.1 magnitude earthquake in Tohoku, Japan. This event also caused a major nuclear disaster at Japan’s Fukushima-Daiichi plant, explained Amy Williamson, a seismology expert at UC Berkeley.
Another advisory occurred in January 2022 when the eruption of the Hunga Tonga volcano generated tsunamis and deadly waves, resulting in fatalities and injuries on Tonga’s islands, Williamson noted.
She recalled that the last comparable earthquake to Thursday’s occurred in June 2005 when a magnitude 7.0 quake struck off the coast near Eureka, triggering tsunami alerts. “These events are rare but possible,” Williamson emphasized.
Fortunately, Thursday’s earthquake took place far enough offshore to minimize the impact, Williamson added.
Between 1850 and 2004, research led by Lori Dengler, a professor emeritus at Cal Poly Humboldt, documented 51 tsunamis in the San Francisco Bay Area. Only two caused damage: the 1960 earthquake in Chile and the 1964 quake in Alaska. The 1964 event, for instance, produced waves nearly 4 feet high at the San Francisco Presidio.
These events underscore the importance of ongoing preparedness and awareness for coastal communities facing the ever-present threat of tsunamis.