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Experts: South Asia is hotbed for quakes
(AP)
Updated: 2005-10-10 09:40 The area stretching across Pakistan into India and
Afghanistan is a hotbed for seismic activity that erupts each time the Indian
subcontinent slams into Asia. But it's the shallow faults that make these
temblors so deadly.
Saturday's magnitude-7.6 quake, centered just outside Pakistan's capital, was
about six miles deep, causing buildings to sway in three nations and killing
thousands as weak structures tumbled, crushing people under mounds of rubble.
"It's how close you are to where the earthquake initiated, because ground
motions fall off very rapidly away from the earthquake," said Harley Benz, a
seismologist who runs the U.S. Geological Survey's National Earthquake
Information Center in Colorado.
"Shallow earthquakes are very dangerous because they're very close to the
built environment, unless they're in remote areas," he said.
In comparison, a 7.5-magnitude earthquake jolted Peru last month. He said it
occurred about eight miles beneath the surface in a more remote area. Only a
handful of people died and several hundred homes were destroyed.
The December magnitude-9.0 earthquake that occurred off Indonesia's Sumatra
island and spawned a tsunami that killed more than 176,000 people in 11
countries occurred about 18.6 miles below the surface.
The crash between the Indian plate and the Eurasian plate in the latest quake
triggered the temblor along a range front that extends about 1,250 miles, Benz
said.
It's the same type of collision that formed the Himalayas, millions of years
ago. As the Indian subcontinent continues to creep about 1.6 inches farther
north every year, mountains are still being formed in the Himalayan, Karakoram,
Pamir and Hindu Kush ranges by the uplift from the collisions, he added.
About 50 million people are at risk of encountering Himalayan quakes in this
area, many of them in the densely populated capitals of Bangladesh, Bhutan,
India, Nepal and Pakistan, according to research published four years ago by
scientists from the University of Colorado who took an in-depth look at the
region's seismic activity.
The area along India's northern border in disputed Kashmir is by far the
hottest spot in that country, said A.K. Shukla, director of India's Earthquake
Risk Evaluation Center. He said the latest quake, unfortunately, will not be the
last and may not be the largest to come.
"It's not a question of surprise, because that area is a highly seismic one,"
he said. "It's not surprising at all."
Saturday's quake was centered about 60 miles northeast of Islamabad in the
forested mountains of Pakistani Kashmir. At least 22 aftershocks followed within
24 hours, including a 6.2-magnitude temblor.
In 1935, a magnitude-7.5 earthquake was recorded in Quetta, India, killing
50,000. In 1974, just north of the recent quake's epicenter, a magnitude-6.2
earthquake occurred, generating 5,800 casualties.
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