Fifty-four years ago today, at 5:36 pm, a powerful magnitude 9.2 earthquake shook the coast of Alaska southeast of Anchorage. It was one of the two strongest earthquakes ever recorded anywhere. The shaking lasted almost 4.5 minutes! The quake killed many people in Alaska, but what may be surprising is that 16 people died in Oregon and California, more than 1,300 miles away. How did this happen?
The Alaska earthquake unleashed a massive tsunami that rushed across the Pacific, reaching the Washington coast in fewer than four hours. The waves reached heights of up to twelve feet in Seaview. Some people returned to the beaches before the tsunami waves had completely subsided.
In those days tsunami warning systems were not as advanced as they are today. Only one tsunami warning center existed in the United States, located at the Honolulu Geomagnetic Observatory on Hawaii. The 1964 earthquake reinforced the need for us to better educate the public about tsunami hazards and to more quickly issue tsunami warnings to local authorities.
Washington is gearing up for ‘the big one’, a great Cascadia subduction zone earthquake predicted to strike right off our coast. But distant source earthquakes like that in Alaska and the 2011 Tohoku earthquake off the coast of Japan are also capable of generating tsunamis in Washington. These tsunamis can speed across the Pacific in a matter of hours, sending huge waves several feet high surging up onto Washington beaches.
Just two months ago, on January 23, a magnitude 7.9 earthquake struck the Gulf of Alaska at 12:31 am. Inhabitants of Alaskan coastal towns evacuated to higher ground, waiting anxiously for the anticipated waves to arrive. Fortunately the tsunami waves remained small and residents were able to return to their homes. More than a thousand miles to the south, the event provided an opportunity for us to consider how we would react to a larger earthquake and the resulting tsunami.
Tsunami inundation maps are an important tool for preparing for tsunamis. The Washington Geological Survey is currently working on improved inundation maps for the entire Washington coast, and recently published new hazard maps for southwest Washington. These maps allow planners to lay out better evacuation routes, which will save lives when the next earthquake happens.
If you spend time on the coast, check out our website for some resources that may help you prepare for a tsunami!
Burke, Jill; Blinder, Alan; Fountain, Henry, 2018, Earthquake Shakes Alaska and Sends a Shudder of Alarm Along the Coast: The New York Times. [accessed March 27, 2018 at https://www.nytimes.com/2018/01/23/us/earthquake-tsunami-alaska.html]
University of Southern California, 1964 Alaskan Tsunami: USC Tsunami Research Group. [accessed March 27, 2018 at http://cwis.usc.edu/dept/tsunamis/alaska/1964/webpages/index.html]
U.S. Geological Survey, The Great M9.2 Alaska Earthquake and Tsunami of March 27, 1964: U.S. Geological Survey. [accessed March 27, 2018 at https://earthquake.usgs.gov/earthquakes/events/alaska1964/]