Content provided by Charles Q. Choi, OurAmazingPlanet
In 1255, before the modern study of earthquakes shed light on some of
their inner workings, a major quake ruptured in the Himalayas, killing
the king of Nepal. Scientists who have studied the historic quake had
originally thought the temblor didn't rupture the Earth's surface, but a
new study suggests it did.
These findings reveal that investigators may one day find more evidence of past earthquakes
in the Himalayas, shedding light on the risks these disasters pose in
one of the most densely populated earthquake-prone zones in the world.
The Himalayas, which are home to the highest mountain peaks in the world,
are the result of the tectonic plate that hosts the Indian subcontinent
slamming into the plate that holds the rest of Asia. As the plates
continue to mash into each other, this titanic activity reshapes the
face of the planet, and earthquakes result — a fact that places many at
risk, given how the population density along the front of the Himalayas
is similar to that of New York City.
Although massive earthquakes have rocked the region — quakes in 1897,
1905, 1934 and 1950 all had magnitudes between 7.8 and 8.9, each causing
tremendous damage — oddly, none were known to have ruptured Earth's
surface. Without evidence of past earthquakes visible at the surface, it
becomes difficult to know when precisely they occurred or how powerful
they might have been, limiting what researchers can say about what
hazards people in the area might face in the future. (Video: What Does Earthquake 'Magnitude' Mean?)
Now scientists have uncovered evidence of not one but two great Himalayan quakes breaking the Earth's surface.
To discover these past ruptures, scientists looked at old aerial photos
of the region and visited the most promising areas during four
one-month-long field trips. The researchers discovered river deposits in
Nepal that had shifted due to movements along the main seismic fault in
the earth that currently marks the boundary between the Indian and Asian tectonic plates.
Using radiocarbon dating, the investigators found these shifts were
apparently caused by great earthquakes in 1255 and 1934, showing that
both quakes ruptured the surface. When it comes to the 1255 quake,
historical records mentioned that many houses and temples in Nepal
collapsed and that one-third of the population of the Kathmandu Valley
was killed. "The incumbent king, Abhaya Malla, too, was killed due to
the same earthquake," researcher Laurent Bollinger, a seismotectonician
at France's Commissariat on Atomic Energy, told OurAmazingPlanet.
The findings suggest that great quakes recur in the region every few centuries.
"Researchers will now be better able to judge earthquake risks in the
area," Bollinger said. Future seismic hazard studies taking these and
any future findings into account can reveal whether or not earthquake
risks in the Himalayas are better or worse than before thought, he
added.
Bollinger and his colleagues detailed their findings this week in the journal Nature Geoscience.
Copyright 2012 OurAmazingPlanet, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
