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Krishna Ramanujan                             For Release:
Goddard Space Flight Center, Greenbelt, Md.   February 5, 2003
(Phone: 301/286-3026)
Kramanuj{at}pop900.gsfc.nasa.gov

Alan Buis
NASA Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-0474)
Alan.d.buis{at}jpl.nasa.gov

RELEASE: 03-13

NASA SATELLITE HELPS SCIENTISTS SEE EFFECTS OF EARTHQUAKES IN REMOTE
AREAS

The unique capabilities of a NASA earth-observing satellite have 
allowed researchers to view the effects of a major earthquake that 
occurred in 2001 in Northern India near the border of Pakistan.

Lead author Bernard Pinty of the Institute for Environment and 
Sustainability in the Joint Research Centre of the European 
Commission, Ispra, Italy, and colleagues from the U.S., France and 
Germany, used the Multi-angle Imaging SpectroRadiometer (MISR) 
instrument on NASA's Terra satellite to observe the effects of a 
massive earthquake in the Gujarat province of India.

Considered one of the two most damaging seismic events in Indian 
recorded history, the Gujarat earthquake struck with a magnitude of 
7.7 (Richter scale) on January 26, 2001. About 20,000 people died and 
another 16 million people were affected. Local residents reported 
fountains of water and sediments spouting from the Earth following the 
earthquake.

As a result of the earthquake's intense ground shaking, 
loosely-packed, water-saturated sediments in the area liquefied, 
behaving more like a liquid than a solid. Ground water flowed up to 
the surface carrying sediments, flooding large areas including ancient 
riverbeds.

"Although the instrument's multiangle and multispectral capabilities 
weren't specifically developed for the purpose of detecting surface 
water, this is an exciting application that merits further 
investigation," said co-author David J. Diner, MISR Principal 
Investigator at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Of 
significance to the Gujarat event is MISR's acquisition of compelling 
evidence of surface water far from the earthquake's epicenter, 
particularly over remote locations inaccessible to teams on the 
ground."

Aside from collecting scientific data in hard to reach places, MISR 
also provides a map overview of what happened and the area affected. 
Such information could be used to detect places where survey teams 
could concentrate their efforts. In this case, MISR data demonstrated 
that specific areas of the Rann were more affected than others by 
dewatering. In addition, the data were instrumental in identifying 
distant sites of liquefaction. Such information may help to validate 
earthquake models and to further constrain relationships between 
earthquake magnitudes and distances of impacts.

"Satellites provide the best way to have a global view of an entire 
region, hundreds of square kilometers can be observed in a few 
minutes, and this happens at any time they fly over a place," said 
Pinty. "In the case of Gujarat, scientists were able to conduct 
surveys near the epicenter but could hardly access other regions also 
affected by the earthquake, partly because of the proximity of 
Pakistani border, a high security and politically sensitive region."

The earthquake's epicenter was located about 80 kilometers (50 miles) 
east of the city of Bhuj, but the MISR instrument found dewatering, or 
release of water and sediment due to compression and liquefaction, as 
far as 200 km (124 miles) from the epicenter. Additionally, there was 
significant dewatering all along an 80-100 kms (50-62 miles) wide 
(south to north) ancient salt lake bed to the north of Bhuj, known as 
the Rann of Kutch.

In the days to weeks following the earthquake, along with ground 
cracks and other types of deformation, water flowed to the surface and 
progressively evaporated in various places. A year later, scientists 
could still observe the consequences of the earthquake across the Rann 
because the water that came up to the surface was very salty. After 
evaporation, the salt was left on the ground and MISR was able to 
detect it also.

The MISR instrument views the sunlit face of the Earth simultaneously 
at nine widely spaced angles, and provides ongoing global coverage 
with high spatial detail. Its imagery is carefully calibrated to 
provide accurate measurements of the brightness, contrast, and color 
of reflected sunlight.

One way MISR registers surface features is by picking up different 
wavelengths of light as they are reflected off the Earth's surface. As 
the satellite passes overhead, MISR collects information over a 400 km 
(248 mile) swath at a spatial resolution of 275 meters (300 yards), 
instantaneously assessing surface features over large regions. Since 
the bright soils of the Rann of Kutch reflect most of the Sun's 
incoming near-infrared radiation, and water bodies absorb 
near-infrared radiation, MISR can detect the contrast and thereby tell 
where dewatering from the earthquake occurred. Changes in reflection 
at different view angles also proved advantageous to identify the 
presence of surface water in other regions.

A paper on the study appears in the current issue of the American 
Geophysical Union's journal, EOS.

For more information, please see:
http://www.gsfc.nasa.gov/topstory/2003/0115gujarat.html

For more information on MISR:
http://www-misr.jpl.nasa.gov/

For European Commission press release, please see:
http://www.jrc.cec.eu.int/pressroom/gujarat.htm

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