Luc Lavier

Seismologic studies have reported seismic velocities reduction and V p / V s ratio changes over damage zones associated with seismogenic faults. The structure and elastic properties of these damage zones indicate the maturity of faults and affect the rupture dynamics of future seismic events. Therefore, they contain critical information about fault properties that could inform seismic hazards. Here we present a geodetic modeling approach to constrain velocity changes and elastic properties of fault damage zones under stress perturbation from nearby earthquakes. Compared to seismic tomographic analysis that is usually limited by resolution, this geodetic approach provides tighter constraints on the elastic properties and geometry of the damage zone at shallow depths. Our results imply that a major component of the shallow strain release is distributed and inelastic. The existence of numerous shallow faults either may indicate a locally detached shallow layer or they are remnants from earlier fault evolution.