Shear wave splitting in eastern and central China: Implications for upper mantle deformation beneath continental margin

Abstract

Eastern China, located at the east margin of the Eurasia plate, is an ideal place to study the deformation pattern of upper mantle beneath continental margin. We investigated the upper mantle anisotropy beneath eastern China by applying teleseismic shear wave splitting measurements. We examined shear wave splitting measurements at 33 permanent stations from CDSN and GSN/IRIS networks in eastern and central China, as well as splitting parameters from a previous regional study. The splitting observations are characterized by apparent diversity of anisotropy pattern in adjacent tectonic domains, including the Southeast China Orogenic Belt and the Yangtze Craton, and the eastern and central North China Craton. Based upon the straightforward relationships between seismic anisotropy and the development of lattice preferred orientation of mineral in upper mantle rocks, we interpret the splitting results in terms of tectonic fabric within the upper mantle. Our interpretation implies that the upper mantle anisotropy beneath eastern China remained the effects of tectonic rejuvenation occurred during the Late Mesozoic to Cenozoic. We proposed that there are possibly two kinds of mechanisms involved in the upper mantle deformation beneath eastern China, depending on the roles of thick root of cratonic lithosphere. One mechanism is the deflecting the asthenospheric flow by the thick root of craton and the other one is the extensional asthenospheric flow causing the craton lost part of its thick root.