SAN FRANCISCO Following a 7.0 magnitude earthquake that rocked a portion of the state on Thursday, Northern California was under a rare and brief tsunami warning alert that put local emergency communication systems to the test.
After about an hour and before the tsunami was predicted to reach, the National Weather Service canceled its advisory. Some counties and localities issued evacuation orders during that hour, while others used text messages and social media to alert the public to the warning. To obtain a better view, some drove to the shore, while others made their way to higher terrain.
People used social media to ask how the NWS decides when to issue alerts and why a warning was issued and then promptly rescinded. Here are additional questions and their answers.
What is a tsunami, exactly?
The Japanese words for port and wave are the origin of the word fortsunami. The National Weather Service describes it as a sequence of extraordinarily lengthy waves that are triggered when an earthquake’s force causes the ocean floor to abruptly rise or sink.
In California, how prevalent are they?
According to the California Geological Survey, more than 150 tsunamis, the majority of which were minor, have hit California’s coastline since 1800.
Minutes after the quake struck west of Ferndale, a small city in coastal Humboldt County, the National Weather Service issued its warning Thursday, and phones buzzed.
Part of it said, “You are in danger.” Avoid the seas. Now go inland or to high ground.
If there wasn’t a big tsunami, why was there an alert?
Early on Friday, the National Weather Service Bay Area stated on the social media site X that the area rarely receives tsunami alerts and that there are many inquiries, annoyances, and even some rage regarding Thursday’s incident.
The most severe of the four tsunami signals is a warning alert, which also includes an advisory alert advising people to avoid the ocean and to remain away from the coast and a watch alert for a potential tsunami. The previous warning alert for California was issued in 2011, following an earthquake in Japan that damaged the California coast to the tune of approximately $100 million.
In essence, before issuing a warning, experts have more time to examine data and verify that a significant tsunami was caused by a far-off, offshore earthquake or other trigger event.
Since tsunami waves may travel up to 500 mph in the deep ocean, Thursday’s earthquake was local and near the shore, necessitating an early high-level alert to give people the most time to get ready, according to the NWS.
“It’s right there in our back doors, so by the time we actually observe it, it might be too late,” NWS Bay Area meteorologist Dalton Behringer stated on Friday.
According to him, scientists utilized Thursday’s time to keep an eye on buoys and gather additional data about the actual earthquake. After observing minimal sea-level displacement and concluding that the earthquake was a strike-slip temblor, which shifts more horizontally and is less likely to produce tsunamis, they canceled the alarm, he added.
“I think it just caught a lot of people off-guard because these things don’t happen very often for us,” he said.
What was the reaction in Northern California?
According to City Manager Miles Slattery, authorities in Eureka, the largest city in Humboldt County, ordered businesses in high-risk areas to evacuate by going door-to-door and sending SMS.
According to him, only a small area of the city was in danger, and the test run on Thursday indicated that evacuees should practice walking rather than driving.
Visitors to the San Francisco Zoo were evacuated, and for about an hour, the commuter light-rail system known as BART in the San Francisco Bay Area halted traffic in all directions via the undersea tunnel connecting San Francisco and Oakland.
In response, authorities in San Francisco sent social media alerts and messages advising citizens to avoid water, beaches, harbors, marina docks, and piers, while police and fire departments in Berkeley evacuated certain parts of the city. According to the San Francisco Department of Emergency Management, move at least one block inland.
Public address system-equipped emergency vehicles also went to check beaches and other low-lying areas for people. However, several detractors said that San Francisco ought to have activated its emergency sirens, which have not been operational since 2019 due to maintenance.
After getting more detailed information from the NWS that any tsunami would impact coastlines north of the Golden Gate Bridge, officials in San Mateo County, which is located just south of San Francisco, thought about sounding its tsunami warning sirens but ultimately decided against it, according to county spokesperson Michelle Durand.
According to her, emergency professionals gathered to watch the situation as fire and police cleaned the beaches, prioritizing public safety and avoiding needless panic.
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