What happens behind the scenes after a tsunami warning is issued?

San Francisco noticed something missing from the city’s emergency response to Thursday’s tsunami warning after a 7.0 magnitude earthquake off the Northern California coast: the old system of emergency sirens were silent. The network of more than 100 old horns has been offline since 2019. They were supposed to be upgraded, but city crews soon found significant problems with their functionality and condition. NBC Bay Area’s Raj Mathai spoke with Heather Marquez, division chief of the Alameda County Fire Department, to understand more about how agencies decide to issue warnings.