Tsunamis are seismic sea waves caused by movements along faults, undersea landslides, volcanic eruptions, or similar incidents. An earthquake or other geological incident in the Pacific Ocean may cause tsunami activity along the California coast. Depending on the location of an incident, a tsunami can reach the California coast in as little as ten minutes or take up to 12 hours. The Alaskan earthquake of 1964 generated a tsunami that killed 12 people in Crescent City, California.
How to know a tsunami may be coming
1. Natural Warning
- Strong earthquake or ground shaking, a loud ocean roar, or the water receding unusually far exposing the sea floor are all natural warnings. Keep calm and quickly move to higher ground away from the coast.
- Not all large earthquakes cause tsunamis, but many do. If the quake is located near or directly under the ocean, the probability of a tsunami
- A tsunami is a not a single wave, but a series of waves. Stay out of coastal areas until an “ALL CLEAR” is issued by an authorized agency.
2. Official Warning
- Tsunami warnings may be issued via radio, television, telephone, text message, door-to-door contact by emergency responders, NOAA weather radios, or in some cases by outdoor sirens.
- Follow the directions in the warning, move away from the beach, and seek more information on local radio or television stations. As Monterey County Office of Emergency Services releases information to the public, 2-1-1 will also provide this information by phone and website advisory posts.
- Follow the directions of emergency personnel who may request you to evacuate beaches and low-lying coastal areas.
When Should I Evacuate?
- Know if you live, work, or play in a tsunami hazard zone.
- Count how long the earthquake lasts. If you feel more than 20 seconds of very strong ground shaking and are in a tsunami hazard zone, evacuate as soon as it is safe to do so.
- If you are on the beach or in a harbor and feel an earthquake, immediately move inland or to higher ground
- Go On Foot. Roads and bridges may be damaged.
- Avoid downed power lines.
- If evacuation is impossible, go to the third or higher floor of a sturdy building or climb a tree. This should only be used as a last resort.
- If you hear that a tsunami warning has been issued but did not feel an earthquake, listen to the radio, television, or other information sources (2-1-1) and follow the instructions.
- If you are outside a tsunami hazard zone, take no action. You are safer staying where you are.
All California coastal counties have or are in the process of posting tsunami hazard zone signs. These signs will show you what areas are safe and what areas may be at risk. Use these signs to guide you to an area that is safe. If no maps or signs are available, go to an area 100 feet above sea level or two miles inland, away from the coast. If you cannot get this far, go as high as possible.
***The preceding information was taken from the “How to Survive a Tsunami” brochure prepared by CalEMA. Their updated tsunami site can be found here.