Recurrence Time Analysis of the 1883 (Mw 8.6 ~ 9.1) Paleo Megathrust Earthquake in West Bengkulu, Sumatra, Indonesia, Using Plate Kinematic Model for Supporting Mitigation Program

Abstract

The great paleo-megathrust earthquake occurred in west Bengkulu-Sumatra on November 25, 1833 and it was estimated to have the magnitude of about Mw 8.6–9.1. This earthquake triggered a tsunami that has 3-4 m height in the Bengkulu coastal and its vicinity. The fundamental earthquake parameter was not known exactly, thus it was difficult to conduct the analysis. We tried to analyze it using scaling law relations of earthquake parameter and magnitude scenarios to estimate the recurrence time based on the plate kinematic model to support the long-term mitigation program. The recurrence time was estimated at 179 years, 250 years, and 314 years if the earthquake is assumed to have a dip-slip mechanism, plate slip rate about 7 cm/year, and magnitude scenarios of 8.6, 8.8, and 9.1 respectively. Then, the recurrence time was estimated at 314 years, 438 years, and 550 years respectively if the earthquake is assumed to have a plate slip rate about 4 cm/year. The other estimation was used the strain rate value of about 1.19 x 10-14/s for Sumatra region and the rigidity modulus of 3.1011 dyne/cm2. We found the recurrence estimation of about 161 years (Mw 8.6), 222 years (Mw 8.8), and 220 years (Mw 9.1) for the dip-slip model. Meanwhile, if this study used all rupture models, the recurrence time of the Bengkulu paleo megathrust earthquake would be about 370 years (Mw 8.6), 558 years (Mw 8.8), and 553 years (Mw 9.1).