Earthquake displacement fields mapped by very precise correlation. Complementarity with radar interferometry

Precise mapping of co- and post-seismic displacement fields is a key issue of the understanding and the modeling of tectonics. Small displacements over large areas, as happen during earthquakes, have been already successfully mapped, at CNES, by radar interferometry. However, mapping them using optical images, with a very high precision also provides useful information. Thanks to a better comprehension of the sampling theory, and therefore to better interpolation capabilities, the correlation technique is now able to provide a local displacement measure with a precision of a hundredth of a pixel. Making images well sampled, choosing the better interpolation techniques, and applying the technique to SPOT images has allowed us to precisely map images of the displacement fields over Landers (California) in 1997 and Izmit (Turkey), where major earthquakes have taken place. The complementarity of this measurement with the radar interferometric measurement is also discussed in the paper