Transcript Earthquake in China - Gallaudet University

Earthquakes in China
Eastern Sichuan province
Near city of Chengdu
2:28 pm
May 12, 2008
• 7.9 magnitude on the
Richter scale
• Shook Beijing (930 mi
N), Shanghai, Thailand,
Vietnam, Pakistan.
• Affected 10 million
people: killing 15, 000
• Lasted 2 min
• Epicenter was only 6
miles deep
Richter Earthquake Magnitude
Effects
Used to measure Earthquake Severity
Less than 3.5 Generally not felt, but recorded.
3.5-5.4
Often felt, but rarely causes damage.
Under 6.0
At most slight damage to well-designed buildings. Can cause
major damage to poorly constructed buildings over small regions.
6.1-6.9
Can be destructive in areas up to about 100 kilometers across
where people live.
7.0-7.9
Major earthquake. Can cause serious damage over larger areas.
8 or greater Great earthquake. Can cause serious damage in areas several hundred
kilometers across.
Damage
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Eighty percent of the buildings collapsed
May be 50,000 people dead
At least six schools collapsed
Telephone and power networks were
destroyed
• Roads were damaged/blocked
• 5 million people homeless
• Dams may be cracked
Landslides
Refugees, soldiers and rescue
workers carry survivors out of
the county town of Beichuan.
The landslide that buried much
of the town is visible in the
background.
Why was there a big earthquake here?
Faults in China
Plate tectonics
Plate tectonics
Why so many earthquakes?
Results of Plate tectonics
• northward collisional convergence (at about
50 mm/y) of the India tectonic plate against
the Eurasian plate.
• begun about 55 million years ago
• has uplifted the Asian highlands and the
Tibetan Plateau to an average elevation of
over 16,000 feet - the highest and largest
plateau on Earth
• India has pushed into Asia at least 1,200 kms
A folded, faults land
The strong folds control the flow of rivers
Sediments collect in rivers
Cities and villages often build on the rivers
Soft sediments shake more in earthquakes
Earthquakes are more destructive
Scientist predict more serious earthquakes
for the future.
Los Angeles computer earthquake
• Movie:
Why so strong?
• Longmenshan Fault
– 155 miles long
– 2 stages: slipped in two places
– 1st – 7 m, 2nd 4 m
• Very hard land in the area
• Waves travel far, and stay strong
• Waves slow down in softer land
• Had at least seven major aftershocks -- measuring
between 4.0 and 6.0 magnitudes
• Have been many serious earthquakes in China