Strong ground motions of the August 18, 2020 Mw 6.6 Masbate, Philippines earthquake were simulated
using the August 11, 2020 Mw 4.9 Masbate, Philippines earthquake records of the Philippine Strong
Motion Network through the Empirical Green’s Function (EGF) method. The fault dimensions and
stress drop ratios were calculated through the source spectral fitting method. A grid search was done to
obtain a set of parameters for the EGF method that explains the observed strong motion data well. These
parameters include the rupture starting point, rupture velocity, rise time, length, and width of the strong
motion generation area (SMGA). The result suggests the rupture started in the shallow southern segment
of the fault plane. The peak ground accelerations (PGAs) from the simulated waveforms are consistent
with the observed PGAs, and a directivity effect was also simulated. The PGAs calculated using a
ground motion prediction equation used for hazard estimations in the Philippines overestimates for three
stations among the four stations analyzed in this study. The peak ground displacements (PGDs) from
the simulated waveforms are underestimates compared to the observed PGDs. The ratio of the size of
the SMGA to the moment magnitude and the ratio of the rise time to the moment magnitude are smaller
than those obtained in previous studies.
Strong Ground Motion, Empirical Green’s Function Method, Peak Ground Acceleration.
Keywords: Strong Ground Motion, Empirical Green’s Function Method, Peak Ground Acceleration.