Crustal Structure of the Indochina Peninsula From Ambient Noise Tomography

The collision between the Indian and Eurasian plates promotes the southeastward extrusion of the Indochina Peninsula while the internal dynamics of its crustal deformation remain enigmatic. Here, we make use of seismic data from 38 stations and employ the ambient noise tomography to construct a 3-D crustal shear-wave velocity (Vs) model beneath the Indochina Peninsula. A low-Vs anomaly is revealed in the mid-lower crust of the Shan-Thai Block and probably corresponds to the southern extension of the crustal flow from SE Tibet. Although the Khorat Plateau behaves as a rigid block, the observed low-Vs anomalies in the lower crust and also below the Moho indicate that the crust may have been partially modified by mantle-derived melts. The strike-slip shearing motions of the Red River Fault may have dominantly developed crustal deformation at its western flank where a low-Vs anomaly is observed at the upper-middle crust.