Crustal anisotropy and deformation in the South China Block

Abstract

The South China Block has experienced complex tectonic evolution. To better understand the pattern and causes of its crustal deformation, we investigate crustal anisotropy using Pms receiver functions derived from teleseismic waveforms recorded at 64 permanent stations of the China Earthquake Networks Center. We obtain anisotropic results at 55 stations in the region. Our results show that the fast wave direction (FWD) is NE-SW in the Jiangnan Orogenic Belt and NNE-SSW in the northern Cathaysia Block, which align with the local tectonic belts, likely reflecting lithospheric extension related to subduction of the Paleo-Pacific Plate. South of ∼28°N in the Cathaysia Block, the FWD is nearly E-W, possibly controlled by the regional stress regime. In the Yangtze River Delta, the FWDs are more variable and predominantly NE-SW and NW-SE, which likely reflect crosscutting fault systems formed during the Paleo-Pacific subduction since the late Permian and mid-to-late Cenozoic tectonic movements. As a whole, the major cause of the crustal deformation in the eastern South China Block is extension associated with the subduction and rollback of the Paleo-Pacific Plate, with additional contributions from the northeastward compression of the Indochina Block, the collision between the South China and North China blocks, as well as the subduction of the Pacific and Philippine Sea plates.