Integrating seismicity parameter analysis and gravity anomaly characterization to enhance the accuracy of earthquake hazard assessment: a case study in Cenderawasih Bay, Indonesia

Abstract

In Cenderawasih Bay, Papua, we improved the assessment of earthquake hazards by integrating seismic parameter analysis with gravity anomaly data. This region, which is known for its seismic activity and complex tectonic structures, offers an ideal setting for disaster risk-mitigation studies. In eastern Indonesia, tectonic plate convergence involves several microplates, creating deformation zones with arc-continent collisions, subduction, shear faults, strike-slip faults, and extensional faults. Our study examined the relationship between earthquake activity and gravity anomalies to enhance the understanding of seismic activity distribution in the Cenderawasih Bay region. Seismicity parameters were analyzed using the IRIS Earthquake Catalog, with aftershocks and foreshocks removed through Reasenberg declustering to focus on independent events. The average values for the seismicity parameters, specifically the magnitudes of completeness (M_c), a, and b, were 4.5, 7.3, and 0.95, respectively, indicating significant tectonic activity. Gravity anomalies were analyzed using a two-dimensional radial power spectrum and three-dimensional Euler deconvolution, which resulted in an estimated depth range for the gravity anomaly source between 15 and 33 km. The results demonstrate that seismic activity is primarily concentrated in the northern region and along the main fault lines of Cenderawasih Bay. There is a correlation between the seismicity parameter b-value and variations in gravity anomalies, with low b-values associated with low to moderate gravity anomalies in regions of high crustal pressure. In contrast, elevated b-values are associated with significant gravity anomalies in low-pressure regions. The seismicity parameter a-value was low to moderate, suggesting tectonic activity. High values correlate with significant gravity anomalies, and the inverse is true. Integrating seismicity analysis with gravity anomaly characterization provides insights into the earthquake distribution in Cenderawasih Bay. This methodological approach not only improves the accuracy of earthquake hazard assessments in the region, but also aids effective disaster risk mitigation.