San Francisco — A rare, brief tsunami warning was issued in Northern California after a magnitude-7.0 earthquake shook parts of the state Thursday, testing local emergency notification systems.
The National Weather Service canceled the warning about an hour later and before the tsunami was expected to arrive. In that time, some cities and counties have issued shelter-in-place orders, while others have issued warnings to people through social media and text messages. Some people headed to higher ground, while others drove to the beach to get a better view.
People have taken to social media to find out why warnings were issued and then canceled so quickly, and how the NWS decides when to send out warnings. Below are answers to additional questions.
The word tsunami comes from the Japanese characters for port and waves. A series of extremely long waves that move when the ocean floor suddenly rises or falls due to energy from an earthquake, according to the National Weather Service.
Since 1800, the California coast has experienced more than 150 tsunamis, most of them minor, according to the California Geological Survey.
Phones rang Thursday as the National Weather Service issued a warning minutes after an earthquake struck west of Ferndale, a small city on the Humboldt County coast.
Some of its contents are as follows: “You are in danger. Stay away from coastal waters. “Move to higher ground or inland now.”
National Weather Service Bay Area Posted Earlier Friday, social platform
The warning alert is the most serious of four tsunami alerts, including a watch alert for a possible tsunami and a caution alert telling people to stay away from the water and the coast. The last time California received a warning was in 2011, when an earthquake in Japan caused an estimated $100 million in damage along the California coast.
Basically, distant offshore earthquakes or other triggering events give scientists more time to analyze data and determine if a large tsunami has occurred before issuing a warning.
But because Thursday’s quake was localized and close to the coast, a hasty high-level warning was issued to give people maximum time to prepare, as tsunami waves can travel at very high speeds of up to 500 mph (800 kph) in deep waters. NWS wrote.
“By the time we actually observe it, it may be too late,” NWS Bay Area meteorologist Dalton Behringer said Friday. “Because it’s right at our back door.”
Scientists used the time Thursday to monitor the buoys and gain more information about the quake itself, he said. They canceled the warning after seeing little sea level change and determined the quake was a strike-slip type, which moves more horizontally and is less likely to cause a tsunami, he said.
“I think a lot of people are caught off guard because this happens to us so often,” he said.
Authorities in Eureka, Humboldt County’s largest city, sent text messages and went door-to-door to order businesses in high-risk areas to evacuate, City Manager Miles Slattery said.
He said only a small portion of the city was at risk and Thursday’s test run showed evacuees should do so on foot rather than by car.
In the San Francisco Bay Area, the commuter light rail system known as BART traveled through an underwater tunnel between San Francisco and Oakland, halting traffic in all directions for about an hour and forcing visitors to the San Francisco Zoo to evacuate.
Reactions varied as in Berkeley, fires and police evacuated certain areas of the city, and in San Francisco, officials sent warnings and messages on social media telling residents to stay off the water, beaches, harbors, marina docks and piers. “Go at least one block inland,” the San Francisco Emergency Management Agency said.
They also went out in vehicles equipped with public address systems to ensure beaches and other low-lying areas were clear of people. But some critics said San Francisco should have turned on the loud emergency siren, which has been offline since 2019 for repairs.
Officials in San Mateo County, south of San Francisco, considered sounding tsunami warning sirens after receiving more comprehensive information from the NWS that a tsunami would impact the shoreline north of the Golden Gate Bridge, but decided against it, spokeswoman Michelle Durand said. army.
She said fire departments and police cleared the beach while emergency crews gathered to monitor the situation, “prioritizing both public safety and preventing unnecessary panic.”
