Reflected and transmitted waves from fault zones

Waves reflected from and transmitted across fault zones can be used to extract information on those zones. Fault zones, characterized as either a low-velocity zone or fracture systems, modify the phase of the waveform and make the seismic response frequency dependent. In this paper we develop an extrapolation scheme for simulating fractures described as linear slip boundaries. Two 9 × 9 linear systems need to be solved if the fracture stiffnesses and the background medium parameters are constant along the fractures. Numerical examples support the validity and efficiency of this approach. Based on the numerical simulation and theoretical arguments, we show that various internal properties of fault zones have differing influence on reflected waves. Fracture stiffness and fracture spacing change significantly the magnitude of the reflected waves, while smallscale random variation in velocity or fracture stiffness has little influence on the wavefields; hence fault zones with small-scale random variation can be modeled with equivalent media.