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PRESS RELEASE. From the San Mateo County Executive’s Office on March 24th, 2025.
Redwood City – Emergency officials today unveiled a dashboard that shows the risk from a tsunami here along the San Mateo County coast as well as communities ringing the bay.
Knowing the risk can help residents and visitors prepare if the threat should arise.
“We cannot control emergencies, but we can control our preparedness,” San Mateo County Supervisor Lisa Gauthier, chair of the Emergency Services Council, said at a news conference at the County’s Regional Operations Center.
Tsunamis remain rare in California but the threat is real.
Local officials created the “San Mateo County Tsunami Hazard Area Dashboard” after state websites crashed following a tsunami alert issued last Dec. 5 by the National Weather Service.
“When this event happens again in the future, should it happen again, we know that County resources will be backing that website up and keeping it available for residents to see,” San Mateo County Supervisor Ray Mueller said.
“But they don’t have to actually wait for that event,” he added. “They can go and see now, which is so important. This week is about preparing the public.”
Most tsunamis are caused by earthquakes below the ocean floor, but underwater landslides and volcanic activity can also cause tsunamis. A tsunami can be imperceptible in the deep ocean but tsunami waves grow and become more dangerous as they approach the shore.
“We are working with community and response partners throughout the county to ensure everyone knows how to use the tsunami dashboard before an emergency happens,” Gauthier said. “Preparedness means checking your status, saving the information and sharing it with your family, your neighborhood and your community networks.”
Depending on a tsunami’s location and size, local emergency managers and residents could have anywhere from hours to minutes of warning.
“What you can do today is log on to this dashboard, see if you are in a tsunami hazard zone or not, whether that’s work, home or play, and get your 72-hour kits prepared. We also want you to sign up for SMC Alert,” the County’s primary warning system, said Dr. Shruti Dhapodkar, director of San Mateo County Emergency Management.
“Together, we face many hazards here in San Mateo County and we need to be prepared for them.”
The dashboard unveiling coincides with Tsunami Awareness Week, which includes preparedness activities and exercises to test regional tsunami response capabilities and coordination with state and federal partners.
Understanding National Weather Service Alerts
The weather service has three levels of alerts.
► Tsunami Watch: A Tsunami is possible, and the arrival is several hours away. Be prepared and monitor the news.
► Tsunami Advisory: There are strong currents/waves in the coastal waters. Stay out of the water and away from the shore, up to a height of 3 feet.
► Tsunami Warning: DANGER! A Tsunami is imminent. Get to high ground immediately and follow evacuation signage.
If you are in a Tsunami Zone (or coastal region) and feel an earthquake, or a loud roaring sound from the ocean, it is possible that a tsunami may arrive within minutes. This may be symbolized by fast-rising water or the water may recede and start coming back up. If you observe any of these natural warning signs, do not wait for an official guidance. Avoid the beaches and move inland and to higher ground.
Evacuation Guidelines
During a Tsunami Warning, evacuate of the Hazard Area to the Non-Hazard Area.
The most critical action following a tsunami warning is to move immediately to higher ground or away from the water. Stay in a safe location until officials confirm it is safe to return. If possible, plan ahead to evacuate to the home of a friend or relative outside the evacuation zone. Locate nearby shelters at Red Cross, if need arises.
Also, be prepared for heavy traffic during this time, and prioritize walking to safety if feasible. If you are in or near a high-rise building, move to at least the fourth floor of a ten-story structure or higher.
If you are not located in the evacuation zone, stay home and away from the roads to allow access to the first responders.
Tsunami Sirens
There are eight tsunami warning sirens on the San Mateo County coast: three in Pacifica; four along what’s called the Midcoast (El Granada, Moss Beach, Half Moon Bay and other communities) and one in Pescadero.
If you hear a steady 3-minute wailing siren, avoid low-lying areas and seek higher ground.
Emergency Alerts
If a Tsunami Warning is issued by the National Weather Service, it will be announced over the Wireless Emergency Alert system to geotargeted mobile devices.
You can also sign up for the County’s mass notification system, called SMC Alert.
Sent via text or email and to landlines, SMC Alert is used to contact you during urgent or emergency situations. Learn more and register for SMC Alert here.
Build a Go Bag
Don’t wait for an evacuation warning build your go bag.
Being prepared means having your own food, water and other supplies to last for several days.
Learn how to build a basic disaster supply kit.
Additional Resources
California Geological Survey Tsunami Update: Tsunami Preparation Guide
Dept of Emergency Management for San Mateo County webpage
Welcome to the San Mateo County Tsunami Hazard Area Dashboard!
Author: mdrag
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