7.0 magnitude earthquake reported off Northern California coast, tsunami warning canceled

Tsunami warnings are a familiar occurrence along the West Coast, where warning sirens and signs remind coastal residents of the potential danger: a massive wall of water could be heading their way.

While the West Coast is often associated with tsunamis, the reality is that any U.S. coastline—including the East Coast—could face this threat under the right conditions.

This was evident on Thursday when residents of Northern California received tsunami alerts shortly after a 7.0-magnitude earthquake struck off the coast of Humboldt County at 10:44 a.m. The warnings indicated a potential tsunami, advising people near Fort Bragg to expect the wave around 11:10 a.m. and further south to San Francisco by 12:10 p.m. Residents in the impacted zone, stretching from Davenport, California, to the Douglas-Lane County line in Oregon, were urged to evacuate inland beyond designated tsunami hazard zones. Roadways closest to the quake’s epicenter were crowded with vehicles moving away from the coast.

Tsunamis occur when underwater earthquakes displace vast amounts of water, generating large, long waves that gain strength as they traverse the ocean. These waves can surge far inland upon landfall, causing severe damage. The term "tsunami," derived from the Japanese words for "harbor wave," reflects their amplified danger in confined coastal areas, where water can be trapped and compressed, creating even higher waves.

Historical examples highlight the devastating potential of tsunamis. In 1964, a 9.2-magnitude earthquake in Alaska caused a tsunami that struck Crescent City, California, five hours later. Waves reached nearly 21 feet, killing 11 people and destroying 29 city blocks. Similarly, the 2011 Tohoku earthquake in Japan, with a magnitude of 9.1, generated a tsunami that led to a nuclear disaster and triggered advisories as far as the San Francisco Bay Area. More recently, the Hunga Tonga volcanic eruption in January 2022 caused a tsunami that reached the Bay Area after devastating parts of Tonga.

Thursday's earthquake off Northern California serves as another reminder of the region's vulnerability. Amy Williamson, a seismology researcher at UC Berkeley, noted the fortunate offshore location of the quake, which minimized its impact. She referenced a similar 7.0 quake in 2005 off Eureka that also prompted tsunami warnings.

Research led by Lori Dengler at Cal Poly Humboldt found that between 1850 and 2004, San Francisco Bay experienced 51 recorded tsunamis. Most caused little damage, but significant waves were observed after major earthquakes, such as the 1960 Chile earthquake and the 1964 Alaska earthquake.

Risk Beyond the West Coast

While the West Coast—California, Oregon, Washington, and Alaska—is at the highest risk due to offshore fault lines, the East and Gulf coasts are not immune. Though they lack major fault lines, distant earthquakes, such as the massive 1755 Lisbon earthquake, could generate tsunamis that reach the Atlantic coastline. Additionally, intense coastal storms can produce meteotsunamis, wave events caused by atmospheric disturbances rather than underwater earthquakes.

One such event occurred on May 15, 2018, when severe thunderstorms spanning from Pennsylvania to Maryland created weather-induced waves along the East Coast. These meteotsunamis had minimal impact, with wave heights ranging from 2.3 to 4.3 inches, but they demonstrate how diverse factors can influence tsunami risk.

Whether on the West or East Coast, the potential for tsunamis underscores the importance of awareness, preparedness, and effective warning systems to minimize loss of life and damage.