Vulnerability in the Java northen region in association with earthquake sources of tectonic origin

Abstract

While threats from the subduction zone off the Java south coast remain persistent, potential sources of a tectonic earthquake centered in the Java northern areas come into play. Despite their enigmatic presence and a clear shift of the sources from the mainland to the north from hypocentre relocation studies, this poses a danger to the community in the Java northern coastlines, increasing vulnerability to earthquake and tsunami hazards. The main aim of this study is thus to evaluate seismic hazards and corresponding analysis, hence assessing vulnerability with respect to the presence of active faults in the northern regions. The methods used here included a-value and b-value calculations inferred from seismogenic zonation made available for the study area and source mechanism determination derived from seismic inversion for two recent events recorded at the Java Sea. The results revealed that the a-value reached 8.55 in Zone 1, reflecting a high seismicity rate over the northern areas of West Java and Banten provinces, and the b-value was about 0.8 in Central Java and East Java, implying a relatively high-stress tectonic regime. The moment tensor solutions yielded sizes M w 6.7 at a depth of 539 km and M w 7.0 at a depth of 594 km with a major double-couple component for the normal faulting types of mechanism, consistent with reference. The results suggest the significance of awareness of seismic threats possible to occur in the Java northern regions; hence more investigations into detailed seismicity in the regions of interest for future research direction.