Implications for fault locking south of Jakarta from an investigation of seismic activity along the Baribis fault, northwestern Java, Indonesia

Abstract

Recent borehole seismic deployments conducted along the Baribis Fault in northwestern Java reveal that it may be active. In this study, we exploit these data to locate proximal earthquakes using a relative relocation technique, estimate their moment magnitudes using a spectral fitting method and compute their focal mechanisms via waveform inversion. We observe that seismicity in the eastern part of the fault is significantly higher than in the west, where a previous GPS study of the region south of Jakarta demonstrated the existence of high compression rates. These observations imply that the western Baribis Fault is locked, and that neighbouring areas, including southern Jakarta and its surroundings, may be highly vulnerable to future sizeable earthquakes when accumulated elastic strain energy is eventually released during fault rupture. Significantly, the current generation of Indonesia’s national hazard maps have not considered seismicity along the Baribis Fault. Our new results therefore call for an urgent reappraisal of the seismic hazard in northwestern Java that carefully takes into account the Baribis Fault and its earthquake potential, particularly in light of its proximity to Jakarta, a megacity that lies at the heart of one of the most densely populated islands in the world.

Geodetic Strain of the Baribis Fault Zone in West Java, Indonesia

“…Based on the estimated principal strain rate in Figure 2, our result indicates that, in general, the northeastern Baribis faults zone (108.0 E, 6.5 S) experiences a significant strain rate (> 50 nanostrain/yr) with a significant and dominant compressional strain. This result is in line with the previous study from [9,10] that the northeastern Baribis Fault in southern Jakarta indicates a high compression rate. Furthermore, Figure 3 depicts our result's distribution of the dilatation rate.…”

“…In the case of Baribis Fault, recently called as West Java Back-arc Thrust (WJBT) [5], an earthquake between Mw7.0-8.0 likely occurred on the Baribis Fault on January 22, 1780, followed by the second event between Mw7.0-7.7 on October 10, 1834 [6]. The existence of this fault has also been studied by several researchers, such from geological mapping using seismic reflection [7], Digital Elevation Model [8], borehole data [9,10] from regional continuous Global Positioning System (cGPS) network, geodetic strain rate [3,[11][12][13], and more complete study used morphotectonic data, seismic reflection, electric resistivity profiles, kinematic, structural field measurements, paleoseismological trenching, and sediment dating [5]. However, none of the above studies used more dense GPS networks in the northeastern Baribis Fault close to the Subang and Cirebon area (Figure 1).…”

“…This study extends our previous work on investigating along northeastern Baribis Fault in West Java, which involved more dense GPS stations. Previously, there was much discussion about whether the Baribis Fault was active [9,10,13].…”

Cultural Coping Strategies to Mitigate Local Impact of Baribis Fault Disasters

“…To date, there exist three predominant themes in the literature on the Baribis Fault. The rst theme pertains to the seismotectonic order, where Java Island, situated in both active and highly active seismotonic arcs, is at risk of frequent and disastrous occurrences (Haryanto et al, 2017; Kusmita et al, 2020;Febyani et al, 2020;Widiyantoro et al, 2022). The second theme explores the historical aspect of the fault, with strong and devastating earthquakes recorded in the area known today as Jakarta and its surrounding areas -including the southern part of Sumatra Island -since the eighteenth and nineteenth centuries, indicating the Baribis Fault as the epicenter of these seismic events.…”

“…Among these active faults is the Baribis Fault, a land fault running east to west across Java. The fault line, which spans over 100 kilometers, traverses through the regions of Tangerang in Banten Province, southern Jakarta, as well as Bekasi, Karawang, and Purwakarta in West Java Province, among others, as indicated by the recent research by Widiyantoro et al (2022). The Indonesian Meteorology, Climatology, and Geophysical Agency (BMKG) con rms that the Baribis Fault moves up to 5 millimeters annually.…”