Analysis of the crustal thickness and Poisson's ratio in eastern Tibet from teleseismic receiver functions

Abstract

Crustal thickness and Poisson′s ratio are two key parameters for investigating tectonic setting and evolution. The H-k technique has become popular to determinate their values in recent years. However, if a complex structure exists in the crust, the reverberated phases from different depths may interfere with each other, resulting in reduction or even absence of the PpPs phase from the Moho, such that the H-k algorithm may not reveal unambiguous estimates of these two parameters. In this paper, the H-k technique is applied to process a synthetic receiver function for a test case, the result of which is compared with that from direct picking of the time delays of the converted and reverberated phases. Then we process the observational data recorded at two stations in eastern Tibet, determine the crustal thickness and the velocity ratio using the two methods, compare the result with that obtained by Xu et al. at the same location, and analyse the potential causes for discrepancy as well as the reliability of the two methods. Finally, the crustal thickness and the Poisson′s ratio in eastern Tibet and Sichuan Basin are determined from the receiver functions recorded at 51 broad-band stations, using the two different methods. The results indicate that the crustal thickness from the time delays is thicker than that from the H-k algorithm near the eastern Himalayan syntaxis, and the crustal Poisson′s ratio in the rigid Sichuan Basin from the time delays ranges from 0.26 to 0.28, which are more reasonable than that from the H-k (0.28 to 0.34). Additionally, the Poisson′s ratio under the faults from the time delays is found to be higher than those on the two sides, which is consistent with the tectonic background and previous study.