A New 3-D plates model near Taiwan from tomography and tectonic implications
speaker ： Li Bo-Kuan
Abstract
Recent tomographic results are used to trace the South China Sea and Philippine Sea subducting slabs, south and northeast of Taiwan along the Manila and Ryukyu trenches, respectively. In particular, the 3-D plates interaction beneath Taiwan is discussed based on a close-up view of the tomographic sections together with earthquake hypocenters distribution.
This study quote different kinds of previous works, include volcanism, tomography, fossils, geodynamics etc. The author use global tomography data and relocated hypocenters trying to build a new model, a transform fault which across northern Taiwan, to combine two subduction system. Although the trend and extension length this transform fault actually prove by only free-air gravity anomaly, the evolution of plate during 10 Ma by global tomography still could reach part of purpose.
The size of the original South China Sea was about twice its present size. The Southern Okinawa Trough rifted during the last 2 ±1 Ma following the propagation of the subduction zone. The Ryukyu Trench has propagated westward from 126oE of longitude (southeast of Miyako Island) to the locus of the present arc-continent collision, along a major lithospheric tear that cut through the continent-ocean boundary first, and then through the continental lithosphere. As a consequence, the southern Ryukyu margin developed progressively from east to west as a subduction zone during the last 8 my. It has been elaborated onto a passive margin which corresponded to the edge of the Eurasian continental shelf bordering the South China Sea prior to Pliocene.
References
Lallemand, S., Font, Y., Bijwaard, H., Kao, H., 2001. New insights on 3-D plates interaction near Taiwan from tomography and tectonic implications. Tectonophysics 335, 229–253.
Rau, R.-J., Wu, F.T., 1995. Tomographic imaging of lithospheric structures under Taiwan. Earth Planet. Sci. Lett. 133, 517-532.