Moho Depth Estimation and The Presence of Subducting Slab in West Sumatra, Jambi, and Riau Islands Regions Using Teleseismic Receiver Function Method: A Preliminary Result

Abstract

The teleseismic receiver function method was used to investigate the crustal structure in West Sumatra, Jambi, and Riau Islands regions. These regions have a high level of seismicity because it is in an active tectonic zone where the oblique subduction between the Indo-Australian and Eurasian plates occurs. This study aims to determine the depth of Moho discontinuity and the presence of subducting slab beneath 6 BMKG seismic stations that form a line perpendicular to the trench and cover 3 different geological zones. PPSI and RASM are in the forearc zone, SKSM is in the volcanic arc zone, and MBBI, JMBI, and DSRI are in the back-arc zone. This study used teleseismic earthquake record data with epicentral distance between 30°-90° from the receiver and magnitude 6 or more. The iterative time-domain deconvolution and receiver function migration techniques were applied to estimate the depth of Moho discontinuity and the presence of subducting slab. The depth of Moho discontinuity in West Sumatra, Jambi, and Riau Islands regions ranges from 21-39 km and generally deeper in the volcanic arc zone possibly due to the isostatic effect. Moho is at a depth of 21-29 km in the forearc zone, 36-39 km in the volcanic arc zone, and 30-36 km in the back-arc zone. Then the subducting slab was observed at a depth of 20 km under PPSI station to 200 km under MBBI station.