DEFINITION: "A tsunami occurs when there is a sudden, large-scale movement of the sea floor that displaces the water above it. While earthquakes are the most common cause, volcanoes and landslides can also trigger tsunamis. Tsunamis move the entire column of water, from surface, to sea floor-- Unlike storm waves, in which wind only moves the water's surface. Multiple waves or surges then ripple out in all directions, moving at speeds of 500 miles per hour or more in deep water. As the tsunami approaches the coast, it slows down significantly to about 25 to 30 miles per hour, causing the water behind it to build up and the tsunami to grow higher." (California State University)
Tsunamis are typically classified as local or distant, depending on the location of their source in comparison to where waves occur. A distant tsunami may take many hours to arrive on the Del Norte coast, whereas a tsunami triggered by local earth movement can arrive in mere minutes.
Remember, if you feel an earthquake:
DROP, COVER, and HOLD ON.
If the shaking is long and strong and you are in the inundation zone (areas in yellow on the map):
Exit your location on foot, being mindful of hazards, and walk to a safe area (areas in green on the map)
The first tsunami wave is often not the largest, and waves can continue for many hours. Stay put in your safe location until officials say it is safe to return.
HISTORY AND SCOPE: There have been over 40 tsunami events recorded in Del Norte County since tidal gauges were installed in 1933. While most of these were small events, four events caused significant damage and a combined 12 deaths. Almost half of all known fatalities from tsunami events on the U.S. west coast have occurred in Del Norte County.
Crescent City is known for devastation it endured in 1964, when a tsunami caused by a large earthquake in Alaska wiped out nearly 30 blocks of the coastal city. The 2011 Tohoku Japan earthquake also sent tsunami waves to Crescent City, destroying much of its harbor.
Click on the red button to be informed of distant source tsunamis through Del Norte County's Community Alert System. When large earthquakes happen far away - such as in Alaska, Japan, or Chile, you may learn that a tsunami is coming hours ahead of arrival. REMEMBER! If you feel a strong and/or long earthquake, that's your natural alert that a local source tsunami may be imminent! It is important that you quickly move to a safe zone.
On March 28, 1964, a 9.2 earthquake struck Alaska, causing tsunami waves near its source and along the U.S. West Coast. Due to its location, offshore topography (bathymetry), and Crescent-shaped shoreline, Crescent City saw the greatest damage outside of Alaska. Four large tsunami waves came ashore in Crescent City, reaching heights of twenty feet, and inundating 29 blocks.
On March 11, 2011 a devastating magnitude 9.1 earthquake and tsunami struck eastern Japan. The same quake sent a tsunami across the ocean, destroying the Crescent City Harbor and leading to our Sister City relationship with Rikuzentaka. Please visit the Redwood Coast Tsunami Work Group page for more information, including video and written testimonials, expert advice, the story of Kamome, and more.
2022 HUNGA TONGA ERUPTION AND TSUNAMI
On January, 15, 2022, The Hunga Tonga-Hunga Ha'apai submarine volcano erupted with the force of 4-18 megatons of TNT, sending tsunami waves across two oceans. While Del Norte County saw little in the way of damage or injuries from the tsunami, waves at our shorelines were as large as 3.7 feet, and continued for five days.