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Here is a screenshot of coseismic interferometry measurements of the 2015 Nepal earthquake. What does it mean?

The star is the epicenter of the earthquake. The screenshot was taken from the UNOSAT live crisis map.

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It is a differential InSAR image that shows wrapped phase in radians which is a measure of the change in range (or distance) between the ground surface and a (more or less) fixed point in space from which the radar images were acquired (keep in mind that two SAR images are required to create an interferogram). To get the actual range change you have to unwrap the interferogram.

You can think of the fringes as contour lines. Areas where spacing between the fringes is tight, represent areas with high deformation, e.g., near the fault. The wavelength of the radar determines the fringe spacing.

A better looking interferogram for the Nepal earthquake is at http://topex.ucsd.edu/nepal/ (made using SAR data acquired by the L-band ALOS-2 satellite operated by the Japanese Space Agency, JAXA).

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