A 3D P-Wave Model of the Crust and Uppermost Mantle Beneath the Malay Peninsula

Abstract

This study employed a computationally efficient Fortran algorithm to construct a three-dimensional P-wave velocity model of the crust and uppermost mantle beneath the Malay Peninsula (MP). Earthquake datasets from both the International Seismological Centre and the Incorporated Research Institutions for Seismology are used to calculate travel-times. Station corrections are determined prior to inversion based on the ak135 model, considering four back-azimuthal directions. The resulting model, validated against previous regional tomographic studies provide enhanced resolution through finer grid parameterization. The inversion results reflect the complex geological and tectonic framework of the MP. At shallow depths (5–10 km), localised velocity variations correspond to known geological formations. The low-velocity anomalies (LVAs) in the crust are consistent with extensive Cenozoic sedimentary basins and reactivated fault zones. The presence of numerous hot springs along the western belt of the MP suggests elevated thermal activity as a key contributor to the LVAs. Deeper anomalies in the lower crust and upper mantle are attributed to multiple subduction and accretion events, remnant subducted slabs, and mantle flow processes. The result of this study reinforces the hypothesis of asthenospheric upwelling and lateral flow beneath the MP, as proposed by previous researchers. The final P-wave velocity model is used to derive S-wave velocity, density, and Poisson's ratio using established empirical relationships. The algorithm offers a cost-effective and rapid solution for seismic tomography, making it useful for foundational studies in regions with sparse station networks and poor azimuthal coverage, such as the MP and other areas with regional proximity to earthquake-prone zones.