SEISMOTECTONIC ANALYSIS B-VALUE IN PAPUA

Abstract

Indonesia stands at the convergence of three active tectonic plates: the Eurasian, Indo-Australian, and Pacific plates, making it highly susceptible to seismic ac-tivity. Papua, located in an active subduction zone, frequently experiences earthquakes due to complex tectonic structures and active fault systems. This study aims to analyse the seismicity in Papua through the calculation of seismo-tectonic parameters, specifically the b-value, to support earthquake hazard miti-gation efforts. The b-value, derived using the Maximum Likelihood method and the Gutenberg-Richter law, indicates the level of stress and brittleness of sub-surface rocks. Lower b-values signify higher stress accumulation and a greater likelihood of large earthquakes. Earthquake catalog data for the Papua region from January 1, 2011 to January 1, 2021, obtained from the International Seis-mological Centre (ISC) with magnitudes in range 3.5 to 8 and depths ≤ 100 km, with the study area is bounded by -15°LS - 5°LU dan 125°-145°BT are used in the analysis. Spatially, the b-value distribution in the Papua region ranges from 0.5 (green) to 2.0+ (red), also the b-values in the Bird's Head region (Sorong Fault) are relatively low, indicating high stress accumulation. Low b-values are found in Mimika Regency and Jayapura, particularly in the southern part of the Yapen–Sorong Fault and the northeastern area around the Mamberamo Fault (ranging from 0.4 to 0.6). Higher seismic energy accumulation in areas with low b-values may indicate a potential for large earthquakes in the future. The results are expected to provide spatial insights into seismic activity in Papua and con-tribute to improving preparedness and reducing seismic risk in the region.