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February 5, 2003
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.
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Contacts:
Krishna Ramanujan
Goddard Space Flight Center, Greenbelt, Md
(Phone: 301/286-3026)
Alan Buis
NASA Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-0474)
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India
Map of India showing area of the Gujurat Earthquake's impact. Credit: Deborah Mclean, NASA
Detail Map of Gujarat Area
Map of the Gujarat region showing locations of documented liquefaction features (where solid matter
behaves more like a liquid)relative to the epicenter of the January 26, 2001 earthquake and mapped
faults. Credit: Martitia Tuttle et al., 2002
Before and After MSIR Images of Gujarat Earthquake
Changes in reflection at different view angles and in the near-infrared spectral region assist with
the identification of surface water. Using such information from the Multi-angle Imaging
SpectroRadiometer (MISR) enables construction of these false-color images obtained on January 15,
2001 (prior to the earthquake) and January 31, 2001 (after the earthquake). In these visualizations,
data from the red band of MISR's most obliquely backward and forward-viewing cameras are displayed as
red and blue, respectively, and data from the near-infrared band of MISR's vertically-downward viewing
(nadir) camera are displayed as green. Surface water in the Rann of Kutch and along the Nagar-Parkar
fault near the Indo-Pakistan border appears in shades of blue and purple. Each image covers an area of
215 kilometers x 156 kilometers. Credit: NASA/GSFC/LaRC/JPL, MISR Team
Sand Blow Deposit in Great Rann
This image shows a sand blow deposit. When waves from a large earthquake pass through wet, loose sand,
patches of sand erupt (from below the surface) onto the ground and form sand blow deposits. This image
shows a sand blow deposit that formed in the Great Rann about 20 km (12 miles) north of the epicenter.
A month after the earthquake, thesand blow and surrounding area were still wet, salt had begun to
precipitate, and iron-oxides had formed in vent area. Credit: M. Tuttle.
Sand Blow in Mud Flats
This sand blow formed in mud flats near Kandla about 50 km (31 miles) south of the epicenter. Multiple
vents are aligned along a ground fissure through which water and sand vented. For scale, a lens cap can
be seen just below the blow hole. Credit: Photograph by M. Tuttle.
Gujarat Region from MISR Instrument on the Terra Satellite
This figure shows a map of the Gujarat region as observed by
the MISR/Terra instrument in the near-infrared band. The rectangle locates the desert region known as
the Rann of Kutch. The ocean appears in dark, featuring a strong absorption of radiation at the
near-infrared wavelength, in contrast to the bright soils of the Rann. Credit: NASA Langley Research
Center Atmospheric Sciences Data Center
Color Composite Map of the Rann of Kutch Based on Data From MISR Instrument on the Terra Satellite
This color composite map was based on MISR/Terra data of the Rann of Kutch over a period of a few weeks
around the earthquake event. The map would appear in shades of grey if the surface liquefaction effects
were not detected by MISR. The blue and red colors highlight the reactivation of old drainage networks
due to the flooding of ancient river beds. The reddish hue reveals areas where the water has evaporated
after a few weeks leaving salt and sand deposits on the ground.
Credit: NASA Langley Research Center Atmospheric Sciences Data Center
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