Simulation of earthquake ground motion via stochastic finite-fault modeling considering the effect of rupture velocity

The finite fault stochastic method is one of the most effective approaches widely used in seismic engineering to simulate near-field high-frequency ground motion (Motazedian and Atkinson in Bull Seismol Soc Am 95(3):995–1010, 2005; Boore in Bull Seismol Soc Am 99(6):3202–3216, 2009). However, the widely used static and dynamic corner frequencies are derived based on the ratio of rupture velocity to shear-wave velocity of 0.69 (Brune in J Geophys Res 75(26):4997–5009, 1970, J Geophys Res 76(20):5002–5002, 1971; Wang in Research on stochastic simulation method for high frequency of ground motions, Institute of Engineering Mechanics, China Earthquake Administration, Harbin, 2017), which obviously eliminates the influence of rupture velocity on corner frequency. In the currently distributed stochastic simulation program, the ratio of rupture velocity to shear-wave velocity is often set to 0.8 and is adopted as one of the important input parameters, which is obviously inconsistent with the assumption when deriving the corner frequency. In order to ensure that the input parameter values are consistent with the basic assumptions used in deriving the parameters, this study redefines the corner frequency associated with the rupture velocity, based on the displacement representation theory providing additional theoretical significance to the corner frequency. Also, the influence of rupture velocity on source rise time is investigated, and the improved corner frequency is verified by the Mw 6.6 Lushan earthquake occurred on April 20, 2013 (local time) in China. The comparison of the static and dynamic corner frequencies indicates that the simulated PGA and PSA obtained by the improved corner frequency are consistent with the observed values. Moreover, the corner frequency proposed in this study can further study the influence of nonuniform rupture velocity on the synthetic results.