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Marin emergency office details countywide response to Dec. 5 near‑source tsunami warning
Summary
Marin County emergency management described a rapid, countywide alerting effort after a Dec. 5 offshore earthquake prompted a near‑source tsunami warning. Officials said Alert Marin and a federal Wireless Emergency Alert were both used, and an after‑action report will recommend faster, more localized messaging.
Stephen Torrance, director of emergency management for Marin County, told the Belvedere Tiburon Joint Disaster Advisory Council on Jan. 28 that the county activated a “MAX” tsunami response and used federal and local alerting systems after an offshore earthquake near Humboldt triggered a near‑source tsunami warning on Dec. 5.
Torrance said the National Weather Service and the National Tsunami Warning Center sent a Wireless Emergency Alert to devices countywide within minutes of the earthquake, and Marin County followed with Alert Marin messages and a countywide partner briefing to provide localized information and Spanish translations.
The county’s duty officer received the initial federal notification at about 10:51 a.m., Torrance said, and most phones reportedly received the first Wireless Emergency Alert between about 10:50 and 10:55 a.m. Torrance said the county sent a localized Alert Marin message directing people to an emergency.marincounty.org map at approximately 11:19 a.m. He described the incident as “the largest emergency alert that has ever been issued by our office.”
Why it matters: Near‑source tsunamis give emergency managers little time to confirm impacts before alerts must go out. Torrance said the county chose a worst‑case MAX phase because limited buoy data and the proximity of the quake meant officials had to act quickly to notify people who could be in inundation zones.
Key facts cited by Torrance: - Initial federal notification timeline: earthquake detected and reported to the National Weather Service about 10:44 a.m.; the National Tsunami Warning Center issued a Wireless Emergency Alert minutes later. - County receipt and duty officer verification: about 10:51 a.m. - Alert Marin follow‑up and localized guidance: message sent about 11:19 a.m.; county convened an 11:30 a.m. conference call with more than 100 partner agencies. - Reach and delivery metrics: more than 1,000,000 points of contact were targeted using county and third‑party data; about 72,000 Opt‑In Alert Marin contacts existed before the event; most text messages delivered in about four minutes and secondary channels (email/landline) took about seven minutes. - Public information activity: the county emergency portal received roughly 26,000 hits in a few hours after the alert was issued.
Torrance emphasized coordination with state and neighboring counties to avoid conflicting advice (for example, one jurisdiction telling people to evacuate north while another told them to go south). He said county staff verified federal data with Cal OES and the National Weather Service before issuing localized recommendations, and that a countywide call helped agencies suspend or continue actions as real‑time forecasts changed.
On opt‑in versus opt‑out for alerts, Torrance said federal rules limit local ability to place cell phones into an opt‑out system. "Legally, we cannot do opt outs for cell phones," he told the council, adding that the county buys supplemental contact data from utilities and vendors for large events and that federal improvements to IPAWS could allow much more hyperlocal Wireless Emergency Alerts within about a year.
Torrance said the office is preparing an after‑action report to recommend clearer, more localized messaging, more accessible public maps, and continued outreach to increase Opt‑In rates. He also noted technical improvements being considered for alert vendors and for making county maps easier to interpret in areas where inundation lines are close together due to topography.
The presentation prompted council questions about confirmation and verification procedures, timeliness during overnight events, and follow‑up public education. Torrance said the county’s duty officer and the state warning center are both 24/7 and that he was “fairly confident” a similar response would have worked at midnight.
The county plans to finalize its after‑action report and pursue process and vendor changes to shorten delivery times and provide clearer local guidance during future near‑source tsunami warnings.
