Pseudo-dynamic rupture implementation in 3D viscoelastic finite-difference code for physics based broadband ground motion synthetics

The paper presents implementation of state-of-the-art pseudo-dynamic rupture in a 3D viscoelastic fourth-order staggered-grid time-domain finite-difference code for the physics-based broadband strong ground motion synthetics. The achieved quantitative improvements in the efficacy of the considered reference pseudo-dynamic rupture model (comprising of random distribution of slip, rake, rise-time of source time function, peak-time as 0.13 times rise-time and rupture arrival time) after the explicit addition of damage zone, fault-roughness and perturbation to the peak-time are highly stimulating in proficient broadband seismic energy radiation and reduction of coherency effects on the high frequency radiations. A final pseudo-dynamic rupture model is implemented with random distribution of all the source parameters along with damage-zone and fault-roughness. An excellent match of the computed pseudo-spectral acceleration using the simulated ground motion by means of the final pseudo-dynamic rupture model with that obtained using NGA-West2 GMPEs for a hypothetical Mw6.5 strike-slip earthquake validates the efficiency of final implemented rupture model. Further, the obtained average of spectral ratio of fault normal and fault parallel ground motions of the order 1.28 (around 1.0) for frequencies 0.8–10 Hz reflects the efficacy to reduce the coherency effect on the high frequency radiations. The observed good match of the simulated ground motion due to the 2004 (Mw6) Parkfield, California earthquake with the earthquake records on rock further validates the efficiency of the implemented final-pseudo-dynamic rupture model in the 3D finite-difference code.