A tsunami warning spurred evacuations in West Berkeley, but feared waves never came

An earthquake off the coast of Humboldt County triggered a tsunami warning and evacuations along the East Bay shoreline Thursday morning. The warning was later called off, and the bay waters remained calm. Credit: Phil Rowntree

For a tense 40 minutes Thursday, much of West Berkeley was under an evacuation order, with weather and geology experts warning that a tsunami could strike the bay shore and much of the Pacific coast.

Businesses in the Fourth Street commercial district shuttered, at least one West Berkeley daycare asked parents to retrieve their children and the busy on-ramp to Interstate 80 at University Avenue was shut down.

But just before forecasters warned the waves would hit, the tsunami warning was canceled and evacuation order lifted. Sailors were back on the San Francisco Bay just an hour after authorities asked people to begin evacuating.

The tsunami warning, which stretched from Santa Cruz to southern Oregon, followed a magnitude 7.0 earthquake off the coast of Humboldt County shortly before 11 a.m.

How far do you live from Berkeley’s tsunami zone? See the hazard map. The ‘probabilities and uncertainties’ of forecasting tsunami damage in Berkeley

That quake turned out not to be the sort likeliest to touch off tsunamis. But geologists and the National Weather Service issue tsunami warnings anytime there is an earthquake that reaches 7.0 or higher, since tsunamis travel at roughly the speed of a passenger jet and can push house-high walls of water into coastal areas.

The ensuring evacuation order from the Berkeley Police Department, issued at 11:24 a.m., told everyone west of Seventh Street to move inland as quickly as possible, while forecasters warned waves could arrive just after noon. It was rescinded at 12:04 p.m.

The order covered the low-lying sections of the city that state geologists say are most at risk, and a few blocks beside. Information on why the city ordered such an extensive evacuation was not immediately available.

Some cities around Berkeley also recommended evacuations along their waterfronts, although a Port of Oakland representative said the port and the Oakland Airport continued operating normally.

Several businesses on Fourth Street hastily closed Thursday after officials ordered people to evacuate much of West Berkeley because of a tsunami warning. The evacuation order and tsunami warning were later lifted. Credit: Ximena Natera, Berkeleyside/Catchlight

Kevin Farley, who co-owns The Cultured Pickle Shop at Bancroft Way and Fifth Street, said he was processing mustard greens and leeks with his staff when the evacuation order came down. They didn’t panic, Farley said — the shop is two blocks away from the area police said would be safe, and they had plenty of time to get there. The alert was canceled right around when they would have left.

“We hung out and continued to work, and our thought was that at noon we would take a walk,” Farley said. “Then it turned out we didn’t even need to do that.”

They did occasionally poke their heads outside and spotted some concerned motorists leaving the area, but not much foot traffic and no widespread panic.

Why did forecasters issue, then cancel, tsunami warnings?

​​Amy Williamson, a research scientist at the UC Berkeley Seismology Lab who previously monitored large earthquakes and issued warnings and advisories at the National Tsunami Warning Center, said Thursday’s earthquake “likely” occurred on a strike-slip fault, in which two tectonic plates slide past each other. Compared to a subduction-zone earthquake, in which two tectonic plates collide and one is pushed under the other, earthquakes on strike-slip faults are less likely to cause a tsunami.

Depth can play a role as well. Earthquakes that occur in shallow water are more likely to cause a tsunami; today’s was in “fairly shallow” water, within the top mile, Williamson said.

A sign hangs in the window of the Sephora store on Fourth Street in West Berkeley, which was one of several businesses evacuated because of a tsunami warning Thursday. Credit: Ximena Natera, Berkeleyside/Catchlight

The decision to issue a tsunami warning for the whole Northern California and Southern Oregon coastline was in line with protocol because of the earthquake’s size, according to Williamson.

Once a warning is issued, the National Tsunami Warning Center leaps into action, pulling in data from its offshore gauges and sensors, and running forecast models to determine things like what time hazardous waves are anticipated to reach shore. A phone alert is sent out and information is then passed along to weather service groups and the state emergency management offices responsible for notifying local authorities.

“If there is a tsunami, it may reach coastlines within minutes or tens of minutes, so they want to provide a warning fast,” Williamson said.

Once forecasters determined the quake would not create a tsunami, the warning was canceled, and police in turn canceled the evacuation in West Berkeley. The city has sent out an online survey asking people to weigh in on how the city handled the situation.

Eric Wittig prepares to sail from Berkeley to Richmond on Thursday, shortly after officials canceled a tsunami warning for San Francisco Bay and much of the Pacific Coast. Credit: Ximena Natera, Catchlight/Berkeleyside

Generally speaking, tsunamis pose more danger to the Pacific coast than to the bayshore. With San Francisco and Marin County positioned between it and the ocean, destructive waves only infrequently strike the East Bay. But if they do reach Berkeley, they can cause hundreds of thousands of dollars’ worth of damage within moments.

The 8.9-magnitude earthquake that struck Japan in 2011 touched off a tsunami surge that hit the Berkeley Marina, thrashing boats and docks. And in 2022 an underwater volcano near Tonga prompted a tsunami warning and an evacuation at the Berkeley Marina and surrounding area.

The California Geological Survey issued new tsunami hazard maps for several counties, including Alameda, in 2021. Berkeley’s hazard area stretches inland to Fifth or Sixth streets from roughly Delaware Street to city border with Albany; between Ashby Avenue and Delaware, the hazard zone mostly extends eastward only to the Union Pacific railway, but does reach further inland near Ashby and University avenues.