Measuring sub-metric displacements induced by earthquakes from satellite images: Application to the Landers (California 1992) earthquake

Ground displacement resulting from the Landers earthquake is computed from a pair of SPOT panchromatic images as described in ¹. Other sources of geometrical deformations (offsets) resulting from local topography, artifacts of the imagery, variations in the satellite attitude during the acquisition process are compensated at the sub-pixel scale. Images are then resampled to be in a cartographic projection using a sine interpolator. Measurements are achieved from a dedicated sub-pixel correlator in the Fourier domain which provides a 2D offset map. Residual biases are compensated from calibration. Amplitude of the remaining high frequency noise is about 0.01 pixel (rms). Most of the low frequency noise can be compensated from modeling. Measurements enables the cartography of the Landers fault with an accuracy of 80 meters. Displacement on the fault is extracted with an accuracy better than 80 meters. Comparison with a model derived from GPS and other geodetic data validates our results. Preliminary results derived from images with a metric resolution provide far more accurate measurements.