Crustal Deformation Patterns in the Tibetan Plateau and Its Adjacent Regions as Revealed by Receiver Functions

Abstract

ABSTRACT In the past decades, several mechanisms (e.g., the crustal flow and thin viscous sheet models) and combinations of them have been proposed to explain the uplift and outgrowth of the Tibetan plateau. These mechanisms, however, cannot account for all the features observed, and the issue is still highly debated. In this study, we computed receiver functions (RFs) at 254 permanent and portable stations in the Tibetan plateau and its adjacent regions to provide large-scale constraints for the crustal deformation. A harmonic analysis, which has been recently proposed to help distinguishing a dipping Moho from crustal anisotropy, was employed here to investigate the accurate crustal anisotropy. We further applied the H-κ stacking technique to determine the crustal composition using the RFs after harmonic correction or moveout correction. Our results showed the following: (1) Harmonic corrections on Ps phases led to average differences of 2.6 km and 0.04 in crustal thickness and in the VP/VS ratio, respectively; notably, the weighting factors of the Ps, PpPs, and PpSs + PsPs phases affected the uncertainties more obviously than the harmonic corrections. (2) The crustal deformation of the central–southern Tibetan plateau was controlled by the faulting and subduction of the Indian plate; meanwhile, faulting played a dominant role in the crustal deformation of the northern and eastern Tibetan plateau. (3) Widespread upper crustal or crustal shortening and thickening should have occurred beneath the entire study region, except for the Chuan–Dian block (which likely underwent tectonic extension). (4) Crustal partial melting might have enhanced the crustal anisotropy, and promoted the accumulation and release of strain, increasing the probability of fracture in the upper crust.