Near-fault broadband seismograms synthesis in a stratified transversely isotropic half-space using a semi-analytical frequency-wavenumber method

Anisotropic behavior occurs in natural soils and rocks, owing to sedimentation and weathering. However, the semi-analytical methods of near-fault broadband seismogram synthesis in the anisotropic medium are still rare. The physical-based frequency-wavenumber method was constructed for broadband seismogram synthesis due to a kinematic hybrid finite-fault source in a stratified transversely isotropic (TI) half-space for the first time. As the crucial foundation of the seismogram synthesis, the Green's function is established by the dynamic stiffness matrix method, effectively and stably modeling the broadband seismic waves propagation in a TI crust. A hybrid method of the kinematic fault source is applied to reasonably combine the low-frequency deterministic parts with the high-frequency stochastic parts, achieving a broadband waves excitation. The theoretical formulations are well-programmed by the FORTRAN code with OpenMP-based parallel technology to implement the fast solution. Compared with the two published results, the correctness of the methodology is well verified. A numerical example of an Mw7.0 scenario strike-slip earthquake is simulated to discuss the difference between TI and isotropic medium in the aspects: (i) attenuation characteristics near the fault area, (ii) rupture directional effect and velocity pulse, and (iii) response spectrum characteristics.