Seismic Tomography of Peninsular Malaysia Inferred from Teleseismic Earthquake

While there are several geological characterizations of Peninsular Malaysia based on the surface geological study, subsurface evaluation based on the seismic data is still lacking. In this work, tomography of the studied region is being investigated through teleseismic earthquake recorded by several seismic stations located along the peninsula. Throughout the tomography analysis, the 1D ak135 global velocity model is used for computing the travel times from the earthquake source to the edge of the 3-D model. In addition, a similar 1-D ak135 model also being used as the starting model for iterative tomography inversion within the 10.5°N to 0.5°S and 96.5°E to 108.0°E boundary region. The seismological data used for this tomography analysis was acquired from 11 stations that shared with International Seismological Centre (ISC) database and Malaysia Meteorological Department (MMD) respiratory. In total, there were 1598 teleseismic earthquakes events recorded in between 2005 to 2016 which satisfy the criteria of 6.0  or larger. Prior to the iterative travel-time computation, the model’s sensitivity and reliability towards the external changes in the data noise and initial conditions were evaluated through the checkerboard resolution test. The synthetic reconstruction images show that the pattern of the checkerboard anomaly is properly recovered at depth of 30 km, 60 km and 90 km with corresponding high and low wave speed have been recovered as per input model. From the 3580 P-wave arrival time, tomography output is generated at 30 km depth interval, from within the crustal layer of 30 km depth, till the uppermost mantle structure of 300 km depth. In addition, the North-South and East-West sections of the peninsula are produced for a better interpretation of the crustal and uppermost mantle layers in the region. In general, the variation from fast to slow wave speed is noticeable in the Northwards trend, apart from KGM station in the Southern Peninsular Malaysia where a slower velocity recorded compared to its surrounding. The Earth’s structure beneath the SRIT, SKLT, SURA, IPM and KUM stations are experiencing a relative negative wave speed perturbation, while the positive wave speed perturbation is recorded beneath JRM, KOM and BTDF stations. The slower wave speed is recorded in Southern Thailand region and continue southward to the North-West part of Peninsular Malaysia, indicated the sedimentation of Semanggol formation that consists of Carboniferous marine shales. It also concluded that Western-Eastern belt separation of the Malay Peninsula is clearly evident from the velocity contrast. In summary, the latest tomography analysis retrieve from teleseismic earthquake provides a new dimension of the subsurface analysis within the Malay Peninsula region.