March 27, 2004
At magnitude 9.2, this was the second-largest quake ever recorded in the world, topped only by a 9.5 in Chile a few years earlier. Its specter, even 40 years later, haunts not only many of those who lost loved ones or who lived through the four minutes of shaking or the quake's legacy of tsunami waves surging into cities and destroying communities, but also those responsible for earthquake monitoring and safety.
"The 1964 earthquake not only jolted Alaska, but it also woke up America to the reality of earthquake risks to lives and property," said Chip Groat, Director of the U.S. Geological Survey (USGS). "This quake showed us that we can't afford to be complacent where earthquakes are concerned, especially in the most seismically active state in the nation."
Research conducted after the quake revealed that on March 27th, 1964, at 5:36 p.m., the crustal plates beneath southern Alaska could resist the strain no longer. The Pacific Plate pushed an average of 30 feet beneath the North American Plate, unleashing the pressure the two masses had built up by pushing against each other for centuries. The shock was roughly equivalent to 100 million tons of TNT exploding -- or the force of about 63,000 atomic bombs the size of the one dropped on Hiroshima. The quake ripped a sub-sea fault 500 miles long (800 km) and 125 miles wide (200 km).
Its effects seem almost biblical in their scale and are a cautionary story not only for Alaska but also for the other 39 U.S. states most at risk of destructive earthquakes. The sea floor immediately rose 36 feet in some places, generating the birth of gigantic tsunami waves that struck the Pacific coast, killing people as far south as Crescent City, California. In all, 131 deaths occurred, most caused by huge tsunami waves that surged into and devastated coastal communities such as Valdez, Seward, Chenega, and Kodiak. Locally, these waves ran up as far as 220 feet high. It was only because the earthquake occurred late in the day of a holiday and in a less populous region that loss of lives and property were not considerably higher.
We've Come a Long Way
Alaska, researchers agree, is ideally suited for earthquake research that helps save lives and property in the state and elsewhere. For the last century, an average of one magnitude 7 earthquake has occurred in Alaska every year.
Yet when the Good Friday earthquake struck Alaska, only two earthquake-monitoring stations existed in the state and scientists had very little direct information to understand how earthquakes occurred in the state.
In response to the Good Friday earthquake, Congress directed the federal government to develop a national research program directed at reducing earthquake risks to lives and property. Congress codified the program into law with the National Earthquake Hazards Reduction Program (NEHRP), now in its 26th year. NEHRP has united seismologists, geologists, engineers and emergency responders at national, state, and local levels in working together in the states to reduce earthquake risks.
An important recent partnership, Groat explained, is the joint effort by USGS, the UAF Geophysical Institute and the state of Alaska to improve earthquake monitoring and reporting capabilities as part of the Advanced National Seismic System (ANSS), a USGS initiative that calls for the addition of 3,000 new earthquake sensors on the ground and 3,000 in buildings in 26 at-risk metropolitan regions across the country. This will upgrade and modernize the regional seismic networks that locate earthquakes and determine magnitudes, replacing aging sensors with modern instrumentation.
In Anchorage, ANSS funded 13 new seismic monitoring stations that have been added to the existing 22 stations operated by the UAF Geophysical Institute, making Anchorage one of the most densely instrumented cities in the nation.
"Over the past 8 years," said Alaska State Seismologist Roger Hansen, "we've teamed up to upgrade and improve the current 350-station seismic network in Alaska with about 40 new stations with modern instrumentation, but this expansion and upgrade needs to continue. Right now, for example, the density of seismic stations in Alaska is only slightly better than that of Oklahoma a state where earthquakes are almost unknown."
In addition, through ANSS, the USGS, the UAF Geophysical Institute and the state of Alaska installed a 32-channel strong motion instrument array in one of the tallest structures in Alaska. Six nearby boreholes complement the instrumentation of the 20-story Atwood Building in Anchorage with sensors placed at depths ranging from 15 to 200 feet. The borehole sensors and the instrumentation in the building will determine how the ground and the building respond to the same earthquake shaking, information essential for engineers to mitigate property damage and loss of life.
Another ANSS prototype being tested and implemented by the City of Anchorage, the UAF Geophysical Institute, the USGS, and NOAA's Tsunami Warning Center is ShakeMap, a sophisticated earthquake analysis system designed by USGS to provide first responders with the information they need to assess the intensity and distribution of strong ground shaking in the minutes following an earthquake. When fully funded by the U.S. Congress, ANSS would operate nationally via real-time seismic networks, available to first responders to rapidly identify areas of heaviest damage and to speed emergency response to those areas in the first critical minutes after a quake occurs. The software tool also can be used by pipeline and utility operators and managers of critical facilities and infrastructure to assess likely damage and to minimize the disruption of business and environmental damage.
"Through working together in local, state, university, and federal partnerships," said Smith, "we've been able to accomplish much more than any group could have possibly accomplished alone."
Today, Alaskans have a better network of seismic stations and the consequent ability to monitor earthquake activity, Smith said. "Despite this considerable progress, much remains to be done to help reduce risks to lives and property in future earthquakes," he added. "For example, much of the regional seismic network in Alaska still uses outmoded 1970s technology, and many areas of the state have no sensors at all. We all look forward to learning more about earthquake processes as a result of our partnerships in years ahead."
SIDEBAR: THE EFFECTS OF THE GOOD FRIDAY QUAKE
By all accounts, the March 27, 1964, Good Friday earthquake and the tsunamis that followed in its wake were simply terrifying, an ordeal to be endured. The quake not only left behind scars still visible on the land, but it also left wounds for those who lost family members and friends in the quake or the tsunamis, some of the victims children.
As the earthquake's first seconds jolted Alaska, the sea floor immediately rose some 36 feet in some places, triggering a huge tsunami that hit the Pacific coast, killing people as far south as Crescent City, Calif. Locally in Alaska, these waves ran up as far as 220 feet high. One eyewitness reported the water rising 15 feet in 5 seconds in Kodiak, Alaska.
In all, 131 deaths occurred, most caused by huge tsunami waves that surged into and devastated coastal communities such as Valdez, Seward, Chenega, and Kodiak. In Valdez, 32 people died in as a result of a tsunami caused by an underwater landslide; tsunamis generated by the earthquake also killed 23 people in the village of Chenega, 12 people in both Whittier and Seward, and 8 in Kodiak.
The effects of the earthquake were also felt worldwide boats off the Gulf Coast of Louisiana sank from the sloshing of water resulting from the quake's force, and the earthquake was recorded on tide gages in Cuba and Puerto Rico. Even wells in Africa sloshed from the reverberating seismic waves.
Earthquake damage was heavy in many towns, including Anchorage, Chitina, Glennallen, Homer, Hope, Kasilof, Kenai, Kodiak, Moose Pass, Portage, Seldovia, Seward, Sterling, Valdez, Wasilla, and Whitter. Anchorage, about 75 miles northwest of the epicenter, also sustained severe damage. About 30 blocks of dwellings and commercial buildings were damaged or destroyed in the downtown area of Anchorage. Some schools were almost
In Valdez, 32 people died in as a result of a tsunami caused by an underwater landslide; tsunamis generated by the earthquake also killed 23 people in the village of Chenega, 12 people in both Whittier and Seward, and 8 in Kodiak.
In the first day there were 11 aftershocks with magnitude greater than 6.0; in the next three weeks there were 9 more. Residents endured thousands of aftershocks in the months following the quake, and felt smaller aftershocks for more than a year.
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