Active Back‐Arc Thrust in North West Java, Indonesia

Abstract

The Java Back‐arc Thrust scars the entire back‐arc area of Java Island, but the faults' nature, timing, and activity remain partly elusive. Characterizing the structure and activity of the seismogenic Java Back‐arc Thrust (historical earthquakes up to 7 Mw) is a cornerstone to evaluate associated geohazards. We focus on the western part of Java Back‐arc Thrust that reaches the megalopolis of Jakarta. We combine morphotectonic data, seismic reflection, electric resistivity profiles, kinematic, structural field measurements, paleoseismological trenching, and sediment dating (optically stimulated luminescence and 14C). Our results suggest that the interplay between the faults, volcanoes, and sedimentary basin modulates the propagation of the fault system across and along‐strike. The West Java Back‐arc Thrust has been active from Pliocene to Recent, but with a laterally variable tempo and tectonic regime. While tectonic activity was sustained for longer times in the eastern part, the West Java Back‐arc Thrust broke through the Jakarta Basin in the west, possibly only since the Late Pleistocene, and partitions into a network of immature transpressive structures. We conclude that the West Java Back‐arc Thrust has a high seismic hazard that requires a careful risk evaluation along its trace, as it threatens the numerous infrastructures of the densely populated West Java.

Continual Advance in Earth Physics Research Group at Physics Study Program, Unesa: What’s new and the next step

“…The results showed that the highest seismicity rates are found in the northern regions of West Java and Banten (corresponding to the highest a-value of 8.55) and the relatively high-stress tectonic regimes in the northern areas of Central Java and East Java (corresponding to the lowest b-value of 0.8). The high seismicity rate in the West Java northern side is supported by [68]. The high-stress tectonic regimes in the north of Central Java and East Java were in line with the results of time-domain moment tensor (TDMT) solutions, giving magnitudes of Mw 6.7 and Mw 7.0 with a resulting major double-couple component for the normal faulting types found for the events in examination, consistent with USGS.…”

3-D shallow shear velocity structure of the Jakarta Basin from transdimensional ambient noise tomography

“… 2017 ), geological (Simandjuntak & Barber 1996 ; Aribowo et al . 2022 ) and seismological (Damanik et al . 2021 ; Widiyantoro et al .…”

“…The Baribis Fault, a backarc thrust fault in West Java, has been active since the Pliocene but is less clearly expressed in its western extent, near Jakarta, than it is farther east (Aribowo et al . 2022 ). Subsequently, Widiyantoro et al .…”

Magnetotellurics (MT) and Gravity Study of a Possible Active Fault in Southern Garut, West Java, Indonesia

“…Current subduction in the south of Java Island is almost trench-perpendicular with a convergence rate from 58 to 65 mm/year from west to east [23]. The neotectonic process generates earthquakes in the subduction megathrust and onshore faults, and most of them rupture in the relatively W-E direction, such as the the Cimandiri [8,24], Lembang [25,26], and Baribis Faults [27,28] in the western part of Java island. Several other seismic activity clusters have been reported with a relative NE-SW direction in the southern part of Java Island in recent years, one of which is the Garsela Fault [29].…”