Explore CGS’ New Tsunami Inundation and Evacuation Maps for Humboldt County

The California coast is beautiful…and vulnerable to dangerous conditions from tsunamis

This week, the California Geological Survey (CGS) — which provides geologic and seismic expertise to the public and other government offices — released two tsunami hazard maps for Humboldt County: one tsunami inundation map and one tsunami evacuation map.

Tsunami Story Map with Humboldt County Evacuation and Inundation Maps
Launch the California Preparedness Guide, an interactive StoryMap which includes the new Humboldt County Tsunami Inundation and Tsunami Evacuation Maps.

This is the first time CGS has helped communities create tsunami evacuation maps. Over the next couple of years, these new maps will be completed for the entire coast.

While uncommon, over 150 tsunamis have hit California’s coast since 1800. A dozen of those tsunamis caused fatalities or significant damage. So, why the new maps for Humboldt County now?

According to Acting State Geologist Steve Bohlen, the maps “reflect an improved knowledge of the potential hazards” since maps were last issued in 2009.

“We have new scientific information and better computer modeling,” says Bohlen, “which has resulted in better forecasts about whether or not an earthquake will create a tsunami, and the path one would take when evacuating. ”

Inundation, Evacuation – What’s the Difference?

Inundation maps show how far inland a tsunami surge could travel in a worst case scenario.

Evacuation maps depict the areas where you should evacuate when a tsunami is expected.

CGS works with local experts and government officials to create these maps.

Tsunami hazard evacuation maps typically go further inland and encompass the tsunami map area so that the community is safe from all tsunami events.

How to Use These Maps

Find your neighborhood on the maps. Then, remember that tsunamis most often follow large earthquakes from either a local or distant area.

When an earthquake occurs just offshore of the North Coast, the ground shaking is your “natural warning.” People should immediately evacuate out of the tsunami hazard area because there may be only a small window of time (minutes) to get to safety.

For tsunamis coming from a distant source, there will likely be an official warning through a siren, text alert, or an emergency message on TV or the radio. Follow the directions provided in the alert message. If you live within an area shown as being likely to be impacted by a tsunami, prepare to move to an area outside both tsunami hazard evacuation area as quickly as possible in case of a tsunami warning.

Evacuation Map Use: Move from the hazard area, marked in yellow, to outside the hazard area, marked in green.

Like earthquakes, tsunamis cannot be predicted, so preparedness is the key,” says Jason Patton, the engineering geologist for CGS who lead the creation of the Humboldt Tsunami Maps.

“It’s important to understand that the entire coast of California has a tsunami hazard — the entire coast.

Patton adds, “the most important thing to remember is this: if you’re on or near the beach and you feel strong ground shaking, head to higher ground immediately.”

Explore the new maps and learn more about tsunami data and preparation:

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