Wednesday, November 28, 2007

alaska earthquake

ANCHORAGE, Alaska (AP) ― A moderate earthquake shook the state's largest city for several seconds Wednesday, but no injuries or damage were reported, authorities said.

The quake, with an estimated magnitude of 5.0, was centered in a remote area about 60 miles northwest of Anchorage, according to the Alaska Earthquake Information Center.

Another earthquake with a magnitude of 3.4 was reported Wednesday morning and was felt in Homer, about 125 miles southwest of Anchorage.
KODIAK -- Residents of Kodiak are receiving a survey also being distributed in other cities in the United States asking how well prepared the communities are for a natural disaster, such as a tsunami or earthquake.

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The survey, funded by the National Science Foundation, was first distributed in Kodiak a year ago.

Other places where the survey is being conducted are communities in California, Hawaii, North Carolina, Oregon, Washington and Puerto Rico.

Liesel Ritchie, research coordinator, visited with city and borough administrators in November 2006 when the first round of questionnaires was given to Kodiak residents.

"The objective has been to look at awareness and preparedness in case a tsunami were to hit Kodiak," Ritchie said.

Unlike many areas where there are earthquakes and volcanoes, Alaska and the Pacific Ocean area are more prepared if a major tsunami were to hit, she said.

According to the Tsunami Research Group of the University of South California, Los Angeles, during the past century, four large and well-documented tsunamis were generated in waters off the Alaska coast. These include the 1946 and 1957 Aleutian events, the 1958 Lituya Bay event and the 1964 Alaska earthquake.

Ritchie said Kodiak residents are likely more sensitive to tsunamis because of memories of the 1964 earthquake and tsunami that brought waters into the middle of town.

The city of Kodiak was struck by 30-foot waves from the earthquake-generated tsunami in 1964, which destroyed most waterfront industries and much of the fishing fleet.

The earthquake, with a magnitude of 8.3 to 9 on the Richter scale, sent waves as far away as Hawaii and Crescent City, Calif.

Several coastal communities on Kodiak Island were damaged as well. The villages of Afognak and Kaguyak were abandoned.

Ritchie said the survey focuses on background attitudes and beliefs about tsunamis, specific awareness, and becoming tsunami ready.

Ritchie is a principal investigator and researcher with the University of Colorado's Natural Hazards Center and the Evaluation Center at Western Michigan University. There is more general awareness of natural disasters recently because of events like Hurricane Katrina and the 2005 Indian Ocean tsunami, she said.

During the first round of the Kodiak survey, approximately 350 people were given the questionnaire. From 125 to 150 people are filling out the survey for the second round, distributed in October.

"We are encouraging anyone who has received a survey to take the time to fill it out," she said.

Results of the survey are expected to be available in spring 2008.
The intense shaking in Fairbanks only lasted three minutes.

Local excitement about the Nov. 3, 2002, Denali Fault earthquake only lasted a few weeks.

But for a handful of scientists in Fairbanks, California and other places across the country, the 7.9 magnitude temblor, one of the largest in Alaska's history, has been on the mind for the past five years.

"Studying this quake is another important piece in the puzzle of understanding how earthquakes work," said Roger Hansen, a seismologist with the Geophysical Institute at the University of Alaska Fairbanks.

Hansen said the large earthquake, centered on the Denali Fault about 90 miles south of Fairbanks, was a sort of dream come true for seismologists ― it was far enough away from large cities to minimize property damage and injuries while close enough to be carefully and thoroughly monitored by researchers.

Not only were Hansen and the other seismologists at the university able to record the initial quake, for the past five years they've been recording and cataloguing the aftershocks ― more than 30,000 so far, most far too small to be discerned with anything but the most sensitive instruments.

The knowledge they've gleaned has helped them better understand the intricate system of faults in Alaska.

But It's not just Alaska researchers who have been engrossed with this five-year-old temblor. Scientists in California are looking to the 2002 quake for a preview of what to expect during the next great quake on the famed San Andreas Fault.

The Alaska earthquake, which resulted in a single injury, could help prevent hundreds of deaths in California during the next big earthquake there.

Lessons for L.A.

The sparsely populated Interior of Alaska and bustling Los Angeles County don't seem to have much in common. But they both have a large strike-slip fault running through them ― the Denali Fault and the San Andreas Fault respectively.

"It's just really scary how similar they are," Ross Stein, a geophysicist with the U.S. Geological Survey, said of the two faults.

Both faults were created by the movement of huge chunks of the Earth's crust sliding past each other, grinding and grating and building up pressure. When that pent-up pressure becomes too much, the two land masses jolt violently sending shock waves through the ground. The more pressure that is built up, the larger the release, the larger the quake.

Because the two faults are so similar in terms of physical size and seismic mechanics, Stein and other scientists in California think that the next great quake on the San Andreas Fault is going to look ― geologically speaking ― like Denali's 2002 temblor.

The difference will be that the Denali quake happened in a remote corner of the world far from major cities whereas the San Andreas Fault is straddled by some of the most densely populated areas of the country, including Los Angeles, the second-largest city in the nation. And that's where Alaska's earthquake has the potential to help save lives.

By analyzing precisely where the earth shook most violently in Alaska five years ago and then by juxtaposing that data onto a map of the San Andreas Fault, Stein and his colleagues have been able to create what they believe is a fairly good picture of which California communities need to be the most prepared.

The hope, Stein said, is that authorities in California will use the scientific data to bolster infrastructure and emergency preparedness plans in the areas likely to be hit the hardest.

An early warning

The mounds of data scientists have been able to collect in Alaska surrounding the 7.9 earthquake are also being used to help seismologists develop early warning systems, Stein said.

Alaska has more than 400 seismic recording stations peppered across the landscape. Those stations provided researches a clear picture of exactly what was happening in the Denali Fault in the moments directly before the quake and in the first few seconds of shaking.

There's a contingent of scientists, Stein said, that believe there are clues in the first seconds of an earthquake that can tell scientists if it's going to be a massive 7.9 or merely a rattling 5.2. If that can be determined in the first few seconds of a quake, that would give authorities about 100 seconds or so before the violent waves traveling through the ground from the quake's epicenter reached cites hundreds of miles away.

"It may not sound like a lot of time, but those seconds can be vital," Stein said.

In the 100 seconds it takes for the ground to really start shaking during a massive earthquake, he said, nuclear power plants can be shut down, fire trucks can be moved out of garages so they are more accessible to emergency responders, schools and hospitals can be put alert.

"If you know it's going to be a big earthquake there's a lot of things you could do," Stein said. "But you need to know whether or not this is going to be big or little."

Far-reaching effects

The Denali Fault earthquake has also helped change some ideas about how far an earthquake's effects can travel. People in Washington reported feeling the ground move shortly after the earthquake and in places as far away as Louisiana and Pennsylvania, placid lakes were suddenly churning.

Robert Smith, a scientist at the University of Utah, has been studying what he sees as a direct link between the Alaska quake and changes in the geology and water table in Yellowstone National Park.

In the minutes and hours following the earthquake, Smith said, there were marked changes in the hydrothermal landscape of Yellowstone, 2,000 miles away from the Denali Fault. Several of the park's geysers, famous for their regularity, suddenly had their eruption schedules thrown out of whack. It took several weeks before the geysers were back on schedule. During that same time, there were 200 to 300 small earthquakes in quick succession throughout the park.

"We were frankly pretty amazed when something of that distance triggered earthquakes here," Smith said. "The Denali earthquake taught us a lesson that things can affect other areas, cause other earthquakes, at greater distances than we thought."

Knowledge to glean

The damage caused by the Denali Fault earthquake has been fixed. The violent shaking is a distant memory for most Alaskans. For many in Fairbanks, the earthquake did nothing more than provide an interesting story or two, but for scientists like Hansen, Stein and Smith, there is still vital knowledge being gleaned from


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