Crustal block rotations in Chinese mainland revealed by GPS measurements

Abstract

We simulate GPS horizontal velocity field in terms of rotations of crustal blocks to describe deformation behavior of the Chinese mainland and its neighboring areas. 31 crustal blocks are bounded primarily by ∼30 Quaternary faults with distinct geometries and variable long-term rates of <20 mm/a, and 1 683 GPS velocities were determined from decade-long observations mostly with an averaged uncertainty of 1–2 mm/a. We define GPS velocity at a site by the combination of motion of rigid block and elastic strain induced by the fault that is locking during a seismic cycle. Model velocities predicted from the preferable block model match well with the GPS velocities to an uncertainty of ∼1.7 mm/a. The slip rates inferred from this model is in a range of 6–18 mm/a for the major faults in Tibet and its margins and 1–4 mm/a in eastern China, consistent with geological observations. Our numerical simulation suggests that the crustal blocks deform internally at a level of ∼10×10−9/a, quite small in comparison with significant deformation localized along fault zones of 50–100 km wide. We conclude that the pattern of continental deformation is not continuous-like but block-like, and the tenet of plate tectonics may be applicable to characterize the active deformation in Asia.