Sediment Thickness and Moho Depth Beneath Western Indonesian Region From Teleseismic Receiver Function

Abstract

The Earth's crust layer and sediment in Western Indonesia has been studied using the inversion of teleseismic receiver function from BMKG’s seismic network. Earthquake events were analyzed in this study with a moment magnitude greater than 6.0 with epicentral distances of 30° to 90°. A total of 60 earthquake events were observed and recorded by 91 stations around the study area. Furthermore, an inversion process was carried out using the initial velocity model from the modification of the AK135f velocity model to obtain the shear wave velocity structure below each stations. The velocity model from the azimuthally stacked vertical receiver function showed that the sediment layer had a relatively medium shear wave velocity value with an average of 2.1 km/s, while the crust layer had 4.60 km/s. The sedimentary layer thickness in this region also varies between 2 km to 10 km. A relatively thick sediment layer of about 8 km to 10 km was observed in two locations, in East Kalimantan associated with the Kutai Basin and Northern part of Sumatera in the North Sumatera Basin, a two major oil producer basinal area in Indonesia. The Moho discontinuity was also found at depths that vary between 16 km to 50 km. In addition, the most shallow Moho depth is 16 km below the North Kalimantan and North part of West Java, while the deeper Moho depth of 50 km is located below East Kalimantan, Central Kalimantan, North Sumatera and South Sumatera.

Depth Estimation of Moho Discontinuity Layer at 5 BMKG Seismic Stations in East Java Using Receiver Function Method

“…The migration results include the depth estimation of Moho Discontinuity layer marked with a black dotted line ranging from 33-36 km and the depth estimation of subduction slab marked with a green dotted line ranging from 75-79 km below GEJI Station. This result is supported by research conducted by[19] which shows that the estimated depth of the Moho Discontinuity layer in the Southern Mountain Zone ranges from 30-40 km [6]. obtained the depth of the Moho Discontinuity layer from the results of the migration of receiver function ranging from 34-40 km in the Southern Mountain Zone.…”