Measuring earthquakes from optical satellite images

Systeme pour l'Observation de la Terre images are used to map ground displa cements induced by earthquakes. Deformations (offsets) induced by stereosco pic effect and roll, pitch, and yaw of satellite and detector artifacts are estimated and compensated. Images are then resampled in a cartographic pro jection with a low-bias interpolator. A subpixel correlator in the Fourier domain provides two-dimensional offset maps with independent measurements a pproximately every 160 m. Biases on offsets are compensated from calibratio n. High-frequency noise (0.125 m(-1)) is similar to 0.01 pixels. Low-freque ncy noise (lower than 0.001 m(-1)) exceeds 0.2 pixels and is partially comp ensated from modeling. Applied to the Landers earthquake, measurements show the fault with an accuracy of a few tens of meters and yields displacement on the fault with an accuracy of better than 20 cm. Comparison with a mode l derived from geodetic data shows that offsets bring new insights into the faulting process. (C) 2000 Optical Society of America. OCIS codes: 100.010 0, 100.2000, 100.6640, 100.2960, 280.0280.