ABSTRACT

In the widely used stochastic finite‐fault method, the scaling of subsource spectra effectively eliminates the dependence of the synthetics on the subsource size but makes the subsource corner frequency lose its function. For this issue, we propose the concept and determination procedure of slip‐correlated corner frequency (SCF) for stochastic finite‐fault modeling of ground motion. The proposed corner frequency is correlated negatively with the local slip and the subsource size and needs no further scaling. First, the problem of subsource scaling in the stochastic method is discussed, and the links between the corner frequency in the stochastic method and the rise time in the deterministic method are analyzed. The way how the rise‐time constraint removes the subsource dependence has reference and enlightenment functions for determining SCF. Then, based on the modeling of rise time in the deterministic method, we use random numbers correlated with the local slip to model the initial corner frequencies and then calibrate the initial values. Subsequently, the 2013 Mw 6.7 Lushan earthquake is used to validate the SCF in three aspects, the dependence on the subsource size, the bias between the observed and synthetic pseudospectral accelerations, and the difference between the synthetics using the dynamic corner frequency (DCF) and SCF. The results show that the SCF can eliminate the subsource dependence and is feasible for high‐frequency simulation. In addition, the SCF performs quite well compared with the DCF, and the negative correlation with slip contributes to removing the overestimation in the very near field. Finally, some discussions on the scaling factor are presented.

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