Effects of recent India quake visible from space
Posted: April 28, 2001

The earthquake that struck western India this January brought water to places that had previously been dry. Shaken by the 7.7 magnitude earthquake, water trapped between tiny grains of sand and layers of mud beneath salt flats was squeezed out and forced to the surface. This water is visible in images from NASA's Multi-angle Imaging SpectroRadiometer (MISR) and a perspective image combining data from the Shuttle Radar Topography Mission (SRTM) and Landsat-7.

Multi-angle Imaging SpectroRadiometer

MISR view of liquefaction effects from the Bhuj, India, earthquake. Photo: NASA/GSFC/LaRC/JPL, MISR Team
On January 26, 2001, a magnitude 7.7 earthquake devastated the Kachchh region in the Gujarat province of western India, killing 20,000 people and destroying buildings, dams and port facilities. These images from NASA's Multi-angle Imaging SpectroRadiometer (MISR) show the affected area. The two upper MISR images are pre- and post-earthquake scenes acquired on January 15 (left) and January 31, 2001 (right). They are "true-color" images made by combining the red, green and blue bands from MISR's nadir (vertically down-looking) camera. The two lower views are "false-color" images made by combining the red bands from three different cameras. Blue is assigned to the camera pointing 70 degrees forward (more sun-facing), green is assigned to the nadir camera and red is assigned to the camera pointing 70 degrees aftward.

The earthquake epicenter was just below the southern tip of the large, white area on the right-hand side of the images, about 70 kilometers (43 miles) northeast of the city of Bhuj. The earthquake may have occurred on the Kachchh Mainland fault, which extends from the region of the epicenter westward along the curved boundary between the darker brown region to the south and the lighter brown area north of it. The compressive stresses responsible for the earthquake are related to the ancient collision of India with Asia and the resulting rise of the Himalayas to the northeast.

That part of the Kachchh region that lies north of the Kachchh Mainland fault includes the Banni Plains and the Rann of Kachchh. It is a low, flat basin characterized by salt pans and mud flats. The salt forms in the Rann of Kachchh as mineral-laden waters evaporate. The salt flats can be seen in the nadir images as highly reflective white and gray areas. During the earthquake, strong shaking produced liquefaction in the fine silts and sands below the water table in the Rann of Kachchh. The shaking caused the mineral grains to settle, squeezing the water out from between the grains and forcing it to the surface. Field investigations have found abundant evidence of mud volcanoes, sand boils and fissures from which salty ground water erupted over an area exceeding 10,000 square kilometers (3,860 square miles). Evidence of the expelled water can also be seen on the MISR images.

Delicate, dendritic patterns of stream channels run throughout many of the salt flats on the post-earthquake image, especially due north of the epicenter. These channels carried water brought to the surface by liquefaction during the earthquake. Areas where shallow surface water is present are much easier to see on the "false-color" multi-angle composite images. Wet areas exhibit a combination of enhanced forward-scattered light due to the reflection by the water, and enhanced backward scattering due to surface roughness or the presence of sediments. This combination results in blue to purple hues.

The region of sand dunes in the upper right and the Indus River valley and delta in the upper left are inside Pakistan. Near the top of the images, an east-west trending linear feature separates the Thar desert of Pakistan from the Rann of Kachchh. This is the Nagar Parkar Fault. On both pre-earthquake images, this feature is evident only from the contrasting brown colors on either side of it. On the post-earthquake images, a narrow ribbon defines the boundary between the two geologic provinces. However, only in the "false-color" image do we see evidence that this ribbon may be a water-filled channel. Because this area is politically sensitive and fairly inaccessible, no field teams have been able to verify liquefaction effects or the presence of water there.

MISR, built and managed by NASA's Jet Propulsion Laboratory, is one of several Earth-observing experiments aboard Terra, which was launched in December 1999. JPL is a division of the California Institute of Technology, Pasadena, Calif.

Shuttle Radar Topography Mission

Perspective view of Rann of Kachchh, India. Photo: NASA/JPL/NIMA
The earthquake that struck western India on January 26, 2001, was the country's strongest in the past 50 years. This perspective view from NASA's Shuttle Radar Topography Mission (SRTM) shows the area of the earthquake's epicenter in the lower left corner. The southern Rann of Kachchh appears in the foreground. The Rann is an area of low-lying salt flats that shows up with various shades of white and blue in this false- color Landsat image. The gray area in the middle of the image is called the Banni plains.

The darker blue spots and curving lines in the Rann and the Banni plains are features that appeared after the January earthquake. Their true colors are shades of white and gray, but the infrared data used in the image gives them a blue or turquoise color. These features are the effects of liquefaction of wet soil, sand and mud layers caused by the shaking of the earthquake. The liquefaction beneath the surface causes water to be squeezed out at the surface, forming mud volcanoes, sand blows and temporary springs. Some of the residents of this dry area were hopeful that they could use the water, but they found that the water was too salty in almost every place where it came to the surface.

The city of Bhuj, India, appears as a gray area in the upper right of the image. Bhuj and many other towns and cities nearby were almost completely destroyed by the January 2001 earthquake. This magnitude 7.7 earthquake was the deadliest in the history of India with some 20,000 fatalities and over a million homes damaged or destroyed. The city of Bhuj was the historical capital of the Kachchh region. Highways and rivers appear as dark lines. Vegetation appears bright green in this false-color Landsat image.

The city of Anjar is in the dark gray area near the upper left of the image. Previously damaged by a magnitude 6.1 earthquake in 1956 that killed 152 people, Anjar suffered again in the larger 2001 earthquake.

The red hills in the center of the image are the Has and Karo Hills, which reach up to 300 meters (900 feet) elevation. Geologists are studying the folded red sandstone layers that form these hills to determine if they are related to the fault that broke in the 2001 earthquake.

This three-dimensional perspective view was generated using topographic data from the Shuttle Radar Topography Mission (SRTM) and an enhanced false-color Landsat 7 satellite image. Colors are from Landsat bands 5, 4, and 2 as red, green and blue, respectively. Topographic expression is exaggerated 5X.

Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyses of the large and growing Landsat image archive. The Landsat 7 Thematic Mapper image used here was provided to the SRTM by the United States Geological Survey, Earth Resources Observation Systems (EROS) Data Center, Sioux Falls, South Dakota.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X- Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200- foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise, Washington, D.C.