Identification of Moho Discontinuity Depth Variations and Subduction Slab in North Sumatra Region Using Receiver Function Method

Abstract

Northern Sumatra is an area with a complex structure of the earth’s crust. This area is very suitable for studying the state of the lithosphere in the subduction zone, where the average distribution of earthquakes with magnitudes greater than 5.0 occurs due to the movement of the subduction zone. This study aims to map the depth of the Moho discontinuity and subduction slab under 3 seismic stations in northern Sumatra, where 3 broadband sensors are 3 components of the BMKG seismograph network (Meteorology, Climatology and Geophysics) using the receiver function method. This study used teleseismic earthquake data with a distance of 30° - 90°. Inversion of the neighbourhood algorithm is used to get the S wave velocity model and the Vp/Vs value used to migrate the amplitude of the receiver function from the time domain to the depth domain. The depth of the Moho in northern Sumatra varies, under the GSI station the Moho depth is shallow ∼ 9 km, while the Moho depth for the other stations is on average 19 - 47 km. The slab is identified at a depth of ∼ 35.5 - 192.54 km below the GSI station to the TSI station where the position of the linear station is towards the Indo-Australian subduction zone. The low speed zone can be identified in the study and found to be in the range of ∼ 10 - 35 km below the surface of the Toba caldera.