Numerical investigation of fracture interface waves

Two-dimensional boundary element simulations are conducted to investigate the properties of Rayleigh-type fracture interface waves generated by a line source located near a single fracture. The fracture is modeled as a displacement–discontinuity boundary condition between two elastic half-spaces with identical properties. Numerical simulations are performed for different fracture stiffnesses, source polarizations, and source depths. Symmetric and antisymmetric fracture interface waves are observed with amplitudes and velocities that are controlled by the ratio of the fracture impedance to the half-space shear wave impedance, as predicted by plane-wave theory [Gu et al., J. Geophys. Res. 101, 827–835 (1996); Pyrak-Nolte and Cook, Geophys. Res. Lett. 14, 1107–1110 (1987)]. When the source is located off the fracture, these waves develop at incidence angles that decrease with source depth.