Grand jury says Humboldt County tsunami warnings need major fixes

The next big offshore quake should not send people in Eureka, Ferndale and the coast scrambling over a message they cannot trust. Humboldt County’s Civil Grand Jury says the warning system still has major gaps, from sirens that are underfunded and mostly nonworking to cellphone alerts that can miss people in the wrong place at the wrong time.

The report goes back to the magnitude 7.0 earthquake offshore of Cape Mendocino on Dec. 5, 2024, about 70 kilometers southwest of Ferndale. A tsunami warning went out to millions of cell phones along the California coast, then was canceled about an hour later. NOAA’s tsunami archive says the wave reached the closest California coast within minutes, but did not exceed 10 centimeters at any sea-level stations. Even so, the alert created confusion far beyond the actual danger zone.

According to the grand jury, the warning package painted an overly broad picture of risk. Inland communities received alerts, and a National Weather Service map appeared to show the tsunami zone reaching 2,000 feet above sea level. In Humboldt County, the result was unnecessary panic and a mass exodus from areas that were not threatened, adding to congestion on Highway 101 in Eureka and making it harder for emergency vehicles to move.

The county’s own tsunami information page says evacuation map boundaries are based on scientific inundation models, but are extended slightly to make them practical for evacuation planning. Its tsunami maps page tells people in the yellow area to evacuate on foot to the nearest green area. The grand jury says that basic instruction still does not reach enough people quickly enough, especially because wireless alerts are tied to a person’s residential address rather than where that phone is physically located. That can leave out visitors, workers and drivers inside a risk area when the warning arrives.

The report also says Humboldt County’s siren system is costly, underfunded and, in most places, not working, leaving large parts of the tsunami zone without coverage. Instead of counting on a future siren buildout, the grand jury urges county and city officials to pursue better-targeted wireless alerts and seek grant money for blue-line pavement markings in Eureka and possibly elsewhere. Oregon and Washington already use blue-line wayfinding to mark exits from tsunami zones, and Washington points communities to Oregon’s method as a model.

Responsibility now falls on the Humboldt County Board of Supervisors, the Sheriff’s Office of Emergency Services and city officials who oversee evacuation planning. The warning problem is not theoretical in a county near the Mendocino triple junction, one of the most seismically complex parts of the West Coast. After the 2024 quake, California’s emergency proclamation said conditions of extreme peril existed in Del Norte, Humboldt and Mendocino counties. The county knows the hazard is real; the report says the remaining job is to make sure the next warning is clear, local and fast enough to save lives.