Early Results of Modelling Subsurface Study in Lake Toba, North Sumatra Using Receiver Function

Abstract

The island of Sumatra was dominated by tectonic interaction between the Indo-Australian plate subducting beneath the Eurasian plate. Lake Toba is one of the results of the collision and had a large eruption several tens of thousands of years ago. The goal of this study was to use the receiver function approach to calculate the depth variation of the Moho layer and identify the presence of a low-velocity zone (LVZ) under Lake Toba, and then compare the results of the deconvolution method. To process data on receiver functions around Lake Toba, 31 data stations from the Lake Toba (LT) project have been chosen, with data sources coming from Geofon (Germany). Water level (frequency domain deconvolution) and iterative time-domain deconvolution are the receiver function methods employed. According to the findings, the depth of the Moho layer varies between 27.5 and 36.95 kilometres, and it thickens to the northeast of Lake Toba. The average depth of Moho is roughly 31.05 km, and the Vp/Vs ratio obtained is around 1.86 on average. The presence of a low-velocity zone was then detected at a depth of 15 km to 25 km in the A-A′ section leading from northwest to southeast on the east side of Lake Toba, and at a depth of 8 km to 22 km in the B-B′ section leading from southwest to northeast across Lake Toba, as indicated by low amplitude. The Investigator Fracture Zone (IFZ) beneath Lake Toba was identified as a magma reservoir and source of volcanic activity. The iterative time-domain deconvolution approach was then used to illustrate the result of the best receiver function in this investigation, which revealed that the arrival time of the Ps wave was more spiky than the result of the water level.