Crustal azimuthal anisotropy in the Jiaodong peninsula: Evidence for the suture between the North China Craton and South China block

Abstract The Jiaodong Peninsula is an ideal region for studying the geodynamics of collision between the North China Craton (NCC) and South China Block (SCB). It is comprised of the Jiaobei massif and the Northern Sulu UHP massif which are separated by the Wulian suture zone (WSZ). Continent-continent collision is necessarily accompanied with crustal deformation. Consequently a detailed crustal deformation pattern would offer observational constraints for understanding the process of the collision. In this study, we measured the crustal azimuthal anisotropy beneath a broadband seismic profile of 20 stations together with 9 permanent stations in the Jiaodong Peninsula. Sinusoidal moveout of Pms phases from radial receiver functions and azimuth-weighted stacking of transverse receiver functions were jointly applied to ensure the reliability of results. In the WSZ, the fast directions are roughly parallel with the NE oriented fault strike, suggesting the Jiaodong Peninsula may preserve fossilized anisotropy in the crust induced by the Triassic collision of the NCC and SCB although have undergone subsequent lithosphere destruction and thinning since the late Mesozoic. We therefore support that the WSZ represents the NCC-SCB suture east of Tanlu fault. In the Jiaobei massif, the crustal azimuthal anisotropy is controlled by both the nearly E-W local stress and NNE-strike detachment faults. The anisotropy beneath the Northern Sulu massif is quite weak with delay times all less than 0.20 s, probably related to the high-density UHP metamorphic rocks which are difficult to generate strong anisotropy inside.