In 2018, a series of earthquakes in Lombok, Indonesia, occurred close together, causing a lot of
casualties and property damage. To quantify the effect of the earthquake, we need to study source
characteristics and conduct source modeling for these earthquakes. Therefore, we simulated the target
event with strong motion data of the smaller event in the surrounding area, which have the closest
hypocenter and similarity of focal mechanism to the target event using the empirical Green’s function
method. Then, we determined the parameters of source modeling, including source dimension ratio (N)
and stress drop ratio (C) to conduct broadband ground motion simulation. After that, did a grid search
calculation to get the best fit values for the strong motion generation area (SMGA). From the grid search,
we obtain the best-fit SMGA size and the rupture starting point that can be used to capture the rupture
propagation and aftershock directions for seismic hazard assessment. The SMGA size indicated that the
western part of Lombok (the region of Mw 6.4 and 7.0) showed lower stress drop than the eastern part
(the region of Mw 6.9) and all were still lower stress drops than the empirical relationship of the SMGA
size to the seismic moment for crustal earthquakes. Furthermore, the relative SMGA locations indicate
a relationship among the foreshock, the mainshock, and the largest aftershock that may trigger each
other and have similar source characteristics with rupture directions.
Keywords:
Earthquake, empirical Green’s function, grid search, strong motion generation area