Slip Rate Estimation of the Lembang Fault West Java from Geodetic Observation

Abstract

The Sunda arc forms the southern border of the Indonesia Archipelago, where the Indo-Australian plate is subducted beneath Eurasia. The age of subducting plate increases from Sumatra in the west to Flores in the east. The increase in age is consistent with an increase in plate dip along the arc and an increasing depth of seismic activity. The motion of Australia with respect to West Java is 68 mm/yr in a direction N11E orthogonal to the trench. A number of active faults characterizing this area include Cimandiri fault, Lembang fault and Baribis fault. This research uses campaign and continues GPS data to make a preliminary estimation of the slip rate of Lembang fault. Our GPS measurements suggest that Lembang fault has shallow creeping and deeper locking portion. The estimated slip rate is 6 mm/yr with fault locking at 3-15 km and shallow creeping with the same rate. While the results are preliminary and we need more data for reliable estimations, we point out that these data can contribute to earthquake risk assessment by constraining earthquake recurrence relationships.