DEFINITION: "An earthquake is a term used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip, or by volcanic or magmatic activity, or other sudden stress changes in the earth." (U.S.G.S).
HISTORY: "In the past 150 years, nearly 40 earthquakes of magnitude 6 or larger have affected Northern California." (Earthquake Country Alliance)
Although they are infrequent, earthquakes of greater than magnitude 6 have occurred in Del Norte County, including a magnitude 6.7 in 1873, with damage centered on Crescent City. The Mendocino Triple Junction to our south has produced several large quakes, including a magnitude 7.2 in 1992. A magnitude 9+ Cascadia Subduction Zone (CSZ) earthquake shook Del Norte County in 1700, and a subsequent tsunami inundated low-lying coastal areas. The CSZ stretches over 600 miles from Northern California to British Columbia. Earthquakes generated by subduction zones are responsible for the largest earthquakes in the world, known as megathrust quakes.
SIGN UP FOR COMMUNITY ALERTS
Click on the red button to be informed about tsunamis generated by earthquakes and other emergencies 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 local earthquake that is strong and/or lasts a long time, that's your natural alert that a local source tsunami may be imminent! It is important that you quickly move to a safe zone. Do not wait for an official alert.
Residents should prepare to be self-sufficient for up to two weeks after a major earthquake, without the benefit of utilities or the initial assistance of response agencies. To prepare your household for an earthquake, view tips and steps from the Redwood Coast Tsunami Work Group. Securing furniture to interior walls, preparing a kit, and keeping a fire extinguisher handy are some simple steps you can take to prepare your household to withstand an earthquake and its aftermath.