DIRECT INVERSION OF RAYLEIGH WAVE GROUP VELOCITY DISPERSION FOR 3D CRUSTAL SHEAR WAVE VELOCITY STRUCTURE IN THAILAND, MYANMAR, AND MALAYSIA

. This study presents a comprehensive investigation of the crustal structure in Thailand, Myanmar, and Malaysia using Rayleigh wave dispersion data from a dense network of 49 seismic stations. A direct inversion approach is employed to derive a high-resolution, 3D shear wave velocity model of the crust, circumventing the traditional intermediate step of constructing group velocity maps. The Fast Marching Method is utilized to compute surface wave travel times and ray paths, ensuring an accurate representation of the complex wave propagation patterns within the heterogeneous Earth structure. The resulting 3D velocity model, with dimensions of 120 (longitude) x 112 (latitude) x 9 (depth) and a total of 120960 grid points, reveals significant lateral heterogeneity that correlates with major tectonic features such as the West Burma terrane, Shan-Thai terrane, Indo-China terrane, and the Sagaing fault. The integration of these findings with existing geological and geophysical knowledge provides critical insights into the tectonic evolution and crustal dynamics of this seismically active region, furthering our understanding of the complex interplay between tectonic processes and crustal architecture in Southeast Asia.