Thailand's crustal properties from tele-seismic receiver function studies

Abstract

Thirty-three seismic stations throughout Thailand were used to infer the crustal thickness, Vp/Vs ratio and Poisson's ratio of Thailand using the receiver function technique. The crustal thickness increases from around 31km in the Shan-Thai terrane (STT) in the west to around 38km in the Khorat Plateau (KP-ICT) located in the Indochina terrane (ICT) in the east. Similarly, the mean Vp/Vs and Poisson's ratios derived here show that Vp/Vs increases from 1.69 to 1.73 from the STT to the KP-ICT, while Poisson's ratio increases from 0.23 to 0.25 from the STT to the KP-ICT. Our results are well supported by geological evidence found at the surface. In addition, we incorporate gravity and magnetic data to constrain the crustal properties of Thailand. The low Poisson's ratios show that the crust of Thailand is mostly felsic. Only the lower crust of KP-ICT is different as it is thicker, denser and has higher mafic composition than the other terranes of Thailand. This special feature in the KP-ICT is required to explain the lower Bouguer anomaly in the KP-ICT. In addition, we interpret the crustal evolution and deformation of these terranes and compare our results with the results from the Vietnam network of the ICT.