Abstract:
West Papua province in eastern Indonesia is located in a complex tectonic setting due to the convergence of the Australian, Pacific, and Eurasian plates. The interaction resulted in several major strike-slip faults, including Koor, Sorong, Ransiki, and Yapen, which are the main seismic routes in the study area. The development of infrastructure needs to address seismic hazards that can be triggered by earthquakes and reduce losses. The research purpose was to estimate and update the seismic parameters in the form of a magnitude of completeness (Mc) and a and b values, using the earthquake catalog from 1964 to 2021. Estimation is done by converting the overall magnitude to moment magnitude (Mw) to simplify the declustering process. West Papua is divided into two main clusters, which show that earthquakes predominantly occur on the fault line with average values of Mc, a, and b of 4.3 ± 0.02, 7.02, and 0.92, respectively. The resulting b value belongs to the intermediate level, presumably related to tectonic characteristics and a strike-slip focal mechanism. The b value around the Ransiki-Yapen fault gives a decreasing trend of 0.84 ± 0.02, indicating the possibility of an increase in stress on the earth’s crust. Analysis of temporal variation of b value for two large earthquakes in 2002 and 2009 showed a decreasing of b value several times before the mainshock then increasing after the event. Fluctuations in the b value may relate to the accumulation and release
of stress, rupture, and aftershocks. This work is likely to prove helpful for estimating seismic risk in West Papua using probabilistic seismic hazard analysis (PSHA).