The most powerful earthquake in United States history was recorded 52 years ago this month. At 5:36 p.m. local time, a magnitude 9.2 earthquake occurred in the Prince William Sound region in Alaska on March 27, 1964.
In all, 139 people were believed to have died as a result of the earthquake. Fifteen died from the earthquake alone, while 106 died in Alaska, 13 died in California and five died in Oregon all related to tsunamis.
In addition to a tectonic tsunami, about 20 smaller and local tsunamis occurred. Smaller tsunamis were created by submarine and subaerial landslides, and tsunami waves were measured in over 20 countries including Peru, New Zealand, Papua New Guinea, Japan and Antarctica.
The earthquake rupture started approximately 15 miles beneath the surface, with its epicenter about 6 miles east of the mouth of College Fiord, 56 miles west of Valdez and 75 miles east of Anchorage. The earthquake lasted more than 4 minutes.
The largest earthquake ever recorded was a magnitude 9.5 in Chile in 1960, ahead of only the Alaskan earthquake.
About three hours after the earthquake, a 4.5-foot wave hit Prince Rupert, British Columbia and later reached the west coast of the Vancouver Island and traveled up to Port Alberni, washing away 55 homes and damaging 375 others. In days immediately after the earthquake, 11 aftershocks were recorded, each with a magnitude greater than 6.0. Aftershocks were felt for more than a year later.
While the earthquake was centered in Alaska, coastal towns in California and Oregon were heavily affected. Twelve people were killed by a tsunami in Crescent City, California, and four children were killed at Beverly Beach State Park in Oregon.
Tsunami preparedness can be found at Cal OES.
Beginning March 20, California will participate in the 2016 Tsunami Preparedness Week. Other similar recognitions of preparedness week are scheduled for Alaska/Guam (March 27-April 2), Hawaii (April), Cascadia Rising (June 7-10), American Samoa (September 24-30) and Oregon/Washington (October).
In California, the National Weather Service and Cal OES will conduct a test of the Tsunami Warning System in Del Norte, Humboldt and Mendocino counties between 11 a.m. and noon on March 23, using “live” tsunami codes to transmit the test message via NOAA All-Hazards Radio, the Emergency Alert System (EAS), as well as local radio and television stations serving the area.
Some communities may also hear the sounds of tsunami warning sirens and observe local first responders practicing their tsunami response activities.
Cal OES provides information on earthquake, tsunami and volcano programs here.
In coastal counties south of Mendocino, the NWS and Cal OES will test the Tsunami Warning System at approximately 10:15 a.m. by transmitting an EAS “Required Monthly Test” message via NOAA All Hazards Radio, and some television and radio stations.
Also on March 23, Cal OES, the California Geological Survey (CGS) and the NWS will conduct a conference call with emergency managers from counties along the coast to test several aspects of the tsunami response, including the ability of the National Tsunami Warning Center (NTWC) to send and coast emergency organizations to receive specific tsunami alert messages.
During the conference call, representatives from the NTWC, Cal OES and CGS will also test their ability to accurately calculate and verify information contained in draft Tsunami Evacuation Playbooks that will be used by local emergency to determine if an evacuation is necessary and for how big of an area.
The test also allows emergency managers from coastal communities to confirm their ability to receive playbook-related information, test their ability to make decisions regarding evacuation, as well as to test their abilities to communicate information to port and harbor officials and to test their reverse notification and other warning systems reaching people in coastal hazard areas.
Other activities scheduled in coastal counties throughout the state during Tsunami Preparedness Week include tests of mass notification systems, tsunami evacuation walk drills, community meetings, workshops, presentations, outreach events, BBQ’s, festivals, 5k runs, and a host of other events.
Additional information about Tsunami Preparedness Week is available at www.tsunamizone.org.