Identification of active faults in West Java, Indonesia, based on earthquake hypocenter determination, relocation, and focal mechanism analysis

Pepen Supendi,Daryono Daryono,Andri Dian Nugraha,Nanang T Puspito,Sri Widiyantoro

doi:10.1186/s40562-018-0130-y

Abstract

We determined earthquake locations through re-picking of P- and S-wave arrival times recorded by BMKG network. Earthquake locations were determined using Hypoellipse code that employs a single event determination method. We then relocated the events using hypocenter double-difference method. We also conducted focal mechanism analysis to estimate the type of fault slip. The results indicate improved hypocenter locations, where patterns of seismicity in West Java were delineated clearly. There are several clusters of earthquakes at depths ≤ 30 km, which are probably related to the Cimandiri, Lembang, and Baribis faults. In addition, there is another cluster in Garut trending southwest-northeast, which is possibly related to a local fault. Histograms of travel-time residuals depict good results, in which travel-time residuals are mostly close to zero. Source mechanism throughout the Lembang fault indicates a left-lateral strike slip in agreement with previous studies. The Cimandiri fault also shows a left-lateral slip, but in the south it shows a thrust fault mechanism. While the source mechanisms of the western part of the Baribis fault indicate a thrust fault and the cluster of events in Garut shows a right-lateral slip if they are related to a local fault.

Highlights

West Java has a complex tectonic structure as this region is affected by the Java subduction zone and faults
The subducted Indo-Australian plate beneath the Eurasian plate along Java Island has produced some active faults in West Java, i.e., Cimandiri, Lembang, and Baribis faults and some volcanoes, i.e., Mt
To figure out earthquake detection capability of the BMKG seismic station network in West Java, we have plotted earthquake cumulative number (Fig. 3a) and the frequency–magnitude relationship (Gutenberg– Richter law) using the data from initial location with the maximum likelihood method provided in the Zmap package (Wiemer 2001)

Summary

Introduction

West Java has a complex tectonic structure as this region is affected by the Java subduction zone and faults. The subducted Indo-Australian plate beneath the Eurasian plate along Java Island has produced some active faults in West Java, i.e., Cimandiri, Lembang, and Baribis faults and some volcanoes, i.e., Mt. Salak and Mt. Gede-Pangrango in Bogor, Mt. Tangkubanparahu in Bandung, Mt. Guntur and Mt. Papandayan in Garut, Mt. Galunggung in Tasikmalaya, and Mt. Ciremai in Kuningan. The western part of Java has high seismic activity (Damanik et al 2012; Sakti et al 2012). Based on the historical earthquake data, large earthquakes occurred

Objectives

Results

Conclusion