The fk-Based Direct Exact Stiffness Matrix Method for Broadband Seismogram Synthesis of a Multi-Scale Crustal Structure Due to Finite Fault Kinematic Sources

Abstract

AbstractBroadband seismograms due to kinematic sources are synthetized using afk-based direct exact stiffness matrix method. The proposed method imposed no limitations on layer-thickness and frequency, by which the multi-scale characteristics of the crustal model (the velocity and thickness vary from centimeter-level in the near-surface to kilometer-level in deep zones) are well captured without extra computations. The formalized exact global matrix for the fine crustal structure attains symmetric and strongly banded features, which is readily tackled with the developed large-scale matrix inverse algorithms. Seismogram synthesis up to 20Hz is calculated to evaluate effects of fault depth, dip and shallow velocity on ground motion. Results exhibit that the duration of velocity pulse is affected by fault depth, whereas the amplitudes are decreased and the hanging wall effects tend to less striking with increasing buried depth. As the fault dip increases, the location of horizontal velocity maximum moves from hanging wall to the footwall side and the amplitude of vertical acceleration becomes larger owing to the fault mechanism. The ground-motion variability is increased with decreasing shallow velocity, and the distribution pattern of acceleration maximum between two source models is remarkably different. The spectral acceleration shows a dramatic increase of energy for random source model considering perturbations, signifying the predominant effects of source model in ground motion simulation.