Tsunami warning systems to activate today in parts of Bay Area, Northern California

Autor: Clare Fonstein
Multiple counties in Northern California, including part of Sonoma County, could expect a test of their emergency alert systems. 

Multiple counties in Northern California, including part of Sonoma County, could expect a test of their emergency alert systems. 

Michael Short/Special to the Chronicle

Tsunami emergency alert systems will be activated for testing in the Bay Area and along the Central and Northern California coast Wednesday morning, according to the National Weather Service. 

The test will be performed between 10:15 and 10:30 a.m. in Sonoma, Napa, Marin, San Francisco, San Mateo, Contra Costa, Alameda, Santa Clara, Santa Cruz, San Benito and Monterey counties, the weather service said.

The emergency alert system will interrupt TV programs, so those watching TV will see a message on their screen informing them that a tsunami warning has been issued, the weather service said. The TV audio will indicate that it is a test. NOAA weather radios will also sound an alert tone. 

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Farther north, the test will occur from 11 a.m. to noon in Mendocino, Humboldt and Del Norte counties and some parts of Sonoma County. In those areas, the weather service said, residents can expect an emergency alert system message sent from the National Weather Service. 

People in the identified coastal tsunami zone will also receive a reverse 911 call, where the county contacts people to warn them of emergencies, from the Mendocino County Office of Emergency Services. The reverse call will only go out to those who signed up for the service, and can take the form of a call, text or email, depending on jurisdiction and what people previously signed up for, according to the National Weather Service. Wednesday’s drill will not include a Wireless Emergency Alert.  

Tsunami sirens will go off along the north coast for three minutes during the drill, officials said. 

A real tsunami warning means that a tsunami was detected and may be approaching your area, according to the California Office of Emergency Services. If you get a tsunami warning, you are advised to get away from the beach and harbor areas. 

The annual test is mimicking a scenario of a tsunami coming from far distance. 

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If a big earthquake occurs along the coast triggering a tsunami, there will not be enough time to issue a warning, according to the National Weather Service. 

In this case people must rely on natural warnings to indicate if a tsunami is imminent. A long earthquake — described by the National Weather Service to be 20 seconds or more — is a natural warning sign of a tsunami, and one can occur just 10 minutes after an earthquake. 

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Clare Fonstein is a reporter who joined the San Francisco Chronicle as part of the two-year Hearst Journalism Fellowship, spending her first year of the program at the Houston Chronicle. In Houston, Fonstein covered breaking news and trending stories.

She was born and raised in the San Francisco Bay Area, then attended Lehigh University in Bethlehem, Pennsylvania, where she majored in journalism and international relations. She previously worked as an intern at the Morning Call, the daily newspaper of the Lehigh Valley, and her college newspaper at Lehigh University.

She can be reached at

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