7 research outputs found
Upper Mantle Shear Wave Velocity Structure of Southeastern China: Seismic Evidence for Magma Activities in the Late Mesozoic to the Cenozoic
Abstract The FujianâTaiwan StraitâTaiwan region, as the active eastern margin of Eurasia since the Mesozoic, has experienced the subduction and retreat of the PaleoâPacific plate from the Middle Mesozoic, the breakup of the continental margin in the early Cenozoic, and then the collision with the Philippine Sea plate in the late Cenozoic. To better understand the tectonic evolution process, a highâresolution 3âD shear wave velocity model of the crust and upper mantle was obtained from surface wave tomography through a direct inversion method. Intermediateâ to longâperiod Rayleigh wave dispersion curves, extracted from teleseismic surface wave with the traditional twoâstation method, were combined with the shortâperiod dispersion curves obtained from ambient noise cross correlation to obtain broader band surface wave data. Two groups of largeâscale lowâvelocity bodies are found to be located in the upper mantle of Fujian and the Taiwan Strait and are inferred to be closely related to the magmatic activities caused by the Mesozoic subduction and Cenozoic extension, respectively. The lowâvelocity anomalies in Fujian are concentrated in the west Cathaysia block in deep regions and split into small bodies in the uppermost mantle, while the lowâvelocity body in the strait is divided into northern and southern parts, corresponding to the twoâstage Cenozoic extension. The velocity gradient was also calculated to estimate the lithospheric thickness, which is only 60â80Â km, and the lithosphereâasthenosphere boundary also features strongly horizontal variations and discontinuities. Our results provide important seismological constraints to investigate the geological and tectonic processes of this region
Inherited state of stress as a key factor controlling slip and slip mode: inference from the study of a slow slip event in the Longitudinal Valley, Taiwan
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