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The Science Behind China's
Sichuan Earthquake
Scientists at the Caltech Tectonics Observatory have started
analyzing the devastating earthquake that struck China's
Sichuan province on May 12. The earthquake occurred in an
area that is deforming as a result of the collision between
two tectonics plates, the Indian plate and the Eurasian plate.
Analysis of seismological measurements indicates that the
quake reached a magnitude of about 7.9, rupturing the front
of the Longmen Shan fault, which marks the eastern edge of
Tibet where the steep front of the Longmen Shan mountain
range overrides the Sichuan basin. The rupture started at
the epicenter and over the next 50 seconds traveled a few
hundred kilometers (about 100 miles) toward the northeast,
where damage is expected to be even more severe than at the
epicenter. The slip (displacement of the two land masses
with respect to each other along the fault line) in some
places is as large as 12 meters (39 feet).
Shaking in the highly populated basin was amplified by sediments,
while shaking in the mountain range triggered landslides
that have caused temporary damming of waterways. Within the
next few days or weeks, more landslides are expected and
some of these dams are expected to undergo catastrophic drainage
causing severe flooding, as happened during the nearby 1933
Diexi quake, magnitude estimated at 7.5.
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In
the figure above, blue arrows show the motion of the land
masses. The white star indicates the location of the 2008
Sichuan earthquake. Colored circles indicate the location
of all earthquakes occurring between 1964 and 2004 with magnitudes
between 4.6 and 9.0. Areas of dense circles indicate boundaries
between plates. The blue arrow on India shows that India
is moving northward at 4 cm/year. The blue arrows on Asia
show Asia's response to India's motion. Southern Asia is
squeezing eastward. The Sichuan earthquake occured at about
the eastern-most region that is responding to this squeezing. More
detail > |
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6 May 2008
Caltech Today:
Tectonics Observatory Hosts 60 Sixth-Graders 
Students on the TO tour learned about earthquakes and tsunamis
in Sumatra, how scientists at Caltech monitor and interpret
seismic activity, and how the Himalaya mountains formed.
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27 May 2008
News Release, Caltech Media Relations:
Stress
Buildup Precedes Large Sumatra Quakes
The island of Sumatra, Indonesia, has shaken many times with
powerful earthquakes since the one that wrought the infamous
2004 Indian Ocean tsunami. Now, scientists from the California
Institute of Technology and the Indonesian Institute of Sciences
are harnessing information from these and earlier quakes
to determine where the next ones will likely occur, and how
big they will be.
29 May 2008
Science Daily:
Stress
Buildup Precedes Large Sumatra Earthquakes: When Can We Expect
The Next One?
Reprint of Caltech Press Release above
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10 April 2008
News Release, Caltech Media Relations:
A
Grand Canyon as Old as the Dinosaurs?
With new geochronologic data from the canyon and surrounding
plateaus, geologists from the California Institute of Technology
present significant evidence that the canyon formed nearly
50 million years earlier than previously thought.
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4 January 2008
LiveScience, MSNBC:
Reason
for earthquake season revealed
New study connects seismic activity with monsoons. Hurricanes
and tornadoes have seasons, but do earthquakes? They do in
the Himalayas, and it's during the winter.
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