Crustal density structure across Thailand delineated from 2D density modelling using gravity data and receiver function

Abstract

This work aims to gather geological and geophysical evidences to construct the crustal density model of Thailand. The initial density models beneath 14-, 16- and 17-degree latitude were delineated from receiver function (RF) data and global crustal density model. The crustal density models were then updated to fit the Bouguer gravity anomaly data (BA) provided by the Royal Thai Survey Department using a 2-D gravity modelling software. The upward continuation technique was also applied to BA for enhancing the deep structure by omitting the influence of shallow structures. The derived crustal density models agree with Thailand’s tectonic setting. The density of the upper crust increases from 2.60 to 2.64 g/cm3 from west to east, from Sibumasu to Khorat Plateau – Indochina terrane. Between these two main terranes, the obtained model reveals the back-arc island, Sukhothai arc and Inthanon Zone, with a density of 2.55 g/cm3. The higher density of the lower crust with the derived mantle boundary from RF, ranging from 30.8 km of Sibumasu in the western to 38 km in the Khorat Plateau – Indochina terrane in the east, fit well with the filtered BA. Low BA that appear in Khorat plateau is not associated with topography in area which correspond to the high-density structure above upper mantle which need further investigation. Although, the developed crustal density models agree with BA, RF and tectonic evolution of Thailand, the additional gravity survey is suggested to enhance the crustal density models along the selected profiles.