Northern California experienced a brief and unusual tsunami warning on Thursday, triggered by a 7.0 magnitude earthquake that jolted the region. The National Weather Service (NWS) lifted the alert after about an hour, prior to the estimated arrival of potential tsunami waves. During that time, various cities and counties initiated evacuation orders, while others relied on social media and text alerts to disseminate information about the situation. While some residents sought higher ground in response, others curiously drove to coastal areas for a closer look.
On social media platforms, many residents expressed confusion over the quick issuance and subsequent cancellation of the tsunami warning, prompting discussions about how the NWS decides to issue such alerts. To provide some clarity, the term “tsunami” derives from Japanese words that mean harbor and wave, referring to a series of exceptionally long waves caused when seismic activity abruptly alters the seabed.
Historically, California’s coastline has endured over 150 tsunami events since 1800, predominantly minor in scale, as recorded by the California Geological Survey. The warning reached mobile devices shortly after the earthquake occurred near Ferndale, a small town located in Humboldt County. The alert instructed locals to evacuate coastal areas and move to higher ground immediately.
Despite the rapid notification, the situation raised questions about why a warning was issued if no substantial tsunami was anticipated. The NWS Bay Area explained on social media early Friday that the region seldom experiences such alerts, leading to public frustration and confusion regarding the incident. Tsunami warnings are the most severe of the four levels of alerts, which also include watches and advisories. The last major warning in California was issued in 2011 following a significant earthquake in Japan that caused extensive damage along the state’s coast.
In cases where an earthquake occurs offshore and far away, scientists typically have more time to analyze data and ascertain the likelihood of a major tsunami before issuing alerts. However, due to Thursday’s earthquake’s proximity to the coast, authorities opted for an immediate high-level alert to provide the best chance for the public to prepare, as tsunami waves can travel at alarming speeds of up to 500 mph (800 kph) in open water, according to NWS representatives.
Dalton Behringer, a meteorologist with NWS Bay Area, noted that when such incidents arise, they can take people by surprise due to their rarity in the region. During the short duration of the alert, scientists monitored buoys and gathered additional information about the earthquake. The warning was lifted after observing minimal changes in sea levels and recognizing that the earthquake was a strike-slip event, which typically causes horizontal shifts and poses less risk for creating tsunamis.
In response to the alert, city officials in Eureka, the largest city in Humboldt County, took proactive measures by communicating evacuation orders through text messages and personal outreach. City Manager Miles Slattery reported that only specific areas faced risk, and that the alert served as a useful test for future evacuations, highlighting the need for residents to evacuate on foot rather than by vehicle.
In the San Francisco Bay Area, the local commuter rail service, known as BART, halted operations through the underwater tunnel linking San Francisco and Oakland, and visitors at the San Francisco Zoo were evacuated as a precaution. Responses varied across the area; Berkeley officials evacuated select neighborhoods, while messages from San Francisco authorities urged residents to avoid beaches, marinas, and low-lying areas, recommending they move at least one block inland.
Emergency responders utilized public address systems to ensure no one was near the waterfront or beaches. Critics, however, expressed dissatisfaction that emergency sirens in San Francisco, which have been out of service since 2019 for maintenance, were not activated. In adjacent San Mateo County, officials opted not to deploy tsunami warning sirens after receiving detailed updates from the NWS indicating that any tsunami impacts were expected to affect regions north of the Golden Gate Bridge, prioritizing the safety and calmness of the community.
