The near-field strong motions during the 1985 Michoacan earthquake (M8) are successfully simulated at broadband frequencies. For the simulation at low frequencies (0 to 1Hz), the modified k-square model (Hisada, 1999) is used by considering the k-squared (wavenumber-squared) distributions of slip (Mendoza and Hartzell, 1989) and the incoherent rupture time. For modeling the slip velocity, the Kostrov-type function with fmax of 10Hz is adopted. The simulated results reproduced well the observed long-period ground motions, including the ramp-function-like displacements with the permanent offsets, and the near-field directivity pulses in the velocities. On the other hand, for the simulation at high frequencies (0.5 to 10Hz), the Kamae-Irikura-Boore method (Kamae, el al, 1998) is used. The results reproduced well the observed accelerations including the directivity effects. Accordingly, the simulated Fourier spectra agree well with those observed at broadband frequencies (0 to 10Hz). The source parameters of an M8 earthquake in a subduction zone can be easily applied to strong motion predictions in other areas using appropriate Green's functions.
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