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CONTACT: Janet Basu, News Service (650) 723-7582;

AAAS REPORTERS NOTE: Zebker will speak at the AAAS meeting in Philadelphia in the session titled "Environmental Remote Sensing: New Developments and Applications" on Tuesday, Feb. 17, at 12:30 p.m.

The Earth moves . . . synthetic aperture radar takes the snapshot

Scientists are using a new satellite-based radar technology called synthetic aperture radar (SAR) interferometry to detect centimeter-sized changes over large areas of the Earth's crust ­ a volcano breathing, a glacier bending as it floats onto the sea, a faultline relaxing after a quake.

Howard Zebker, Stanford associate professor of geophysics and electrical engineering and one of the developers of the SAR technology, described some of its uses in a session on Tuesday, Feb. 17, at the annual meeting of the American Association for the Advancement of Science in Philadelphia.

Zebker said, "Interferometric SAR is beginning to be used to study subtle phenomena, such as the deformations of volcanoes before eruptions. Scientists are working with it to measure a whole host of land subsidence issues such as withdrawal of water, oil or other fluids from the Earth's crust. In addition to studying the large co-seismic motions that occur during earthquakes, SAR is being used to gather more subtle data about the relaxation in stress after an earthquake, and to look for gradual buildup of stress over years ­ movement that often is not detectable by seismograms.

"In addition," he said, "scientists continue to use interferometric SAR as a tool for mapping the flow of ice sheets and glaciers, over large remote areas of the Earth, principally for large-scale modeling of the Earth's climate and possible man-induced changes such as are being discussed at the global warming conference in Japan."

For a more complete description of SAR interferometry, see the enclosed articles that appeared last year in Stanford Report and Pacific Discovery Magazine.


By Janet Basu

For additional information, see Stanford Report at

And check Howard Zebker's home page at

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