RADAR SNAPSHOTS REVEAL QUAKE MOVEMENT IN SHARP DETAIL
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Image Advisory
RADAR SNAPSHOTS REVEAL QUAKE MOVEMENT IN SHARP DETAIL
New spaceborne radar data of California’s October 16 7.1
magnitude earthquake near the desert town of Twentynine Palms
show ground movement with millimeter precision four days after
the temblor.
The new radar measurements combine two images taken by the
European Space Agency’s European Remote Sensing-2 satellite on
September 15, about one month before the quake, and October 20,
four days after the quake. Overall, the image shows a complex
pattern of displacements that provides new insights into the
mechanisms of the earthquake, which fractured the region’s Lavic
Lake fault. Scientists refer to the event as the Hector Mine
earthquake.
The images are available at
http://www.jpl.nasa.gov/hectormine.
Each color is a contour of measurable ground displacement
and the amount of displacement between successive contours of the
same color is 10 centimeters (4 inches). Taken from space at a
23-degree angle, the contours can be counted to indicate that the
ground moved as much as 5 meters (17 feet) near the fault.
The technique of combining images from spaceborne radar
instruments to discern elevation and surface change is called
synthetic aperture radar interferometry. This scientific tool is
quickly becoming a standard method for studying active tectonics
and other natural processes both on Earth and on other planets
and moons. Synthetic aperture radar interferometry allows
seismologists and geophysicists to study regions of a planet with
unprecedented precision and resolution over days, months and
years, and to monitor processes such as volcanoes, glacier flows
and landslides.
The European Remote Sensing-2 satellite is managed by the
European Space Agency headquartered in Paris, France. Radar
analysis was carried out by JPL’s imaging radar group for NASA’s
Earth Science Enterprise, Washington, DC. JPL is a division of
the California Institute of Technology, Pasadena, CA.
