High-resolution Imaging of Fault Zone Structures with Seismic Fault Zone Waves

Abstract

Large fault zone (FZ) structures with damaged rocks and material discontinuity interfaces can generate several indicative wave propagation signals. High crack density may produce prominent scattering and non-linear effects. A preferred crack orientation can lead to shear wave splitting. A lithology contrast can produce FZ head waves that propagate along the material interface with the velocity and motion polarity of the faster medium. A coherent low velocity layer may generate FZ trapped waves. These signals can be used to obtain high resolution imaging of the subsurface structure of fault zones, and to track possible temporal evolution of FZ material properties. Several results have emerged from recent systematic analyses of such signals. The trapped waves are generated typically by ~100-m-widem-wide-widewide layers that extend only to ~3–4 km depth and are characterized by 30�–�0� velocity reduction and strong attenu�–�0� velocity reduction and strong attenu–�0� velocity reduction and strong attenu