Transition tectonics of northern Taiwan induced by convergence and trench retreat

Abstract

As an active collision zone between the Luzon arc and the China continental margin, the Taiwan mountain belt is undergoing strong crustal shortening and rapid uplift, especially in its south-central part. In contrast, northeast Taiwan, located near the junction between the Taiwan orogen and the Ryukyu arc, is subject to both the compressional force exerted by the indentation of Philippine Sea plate and the tensile force induced by trench retreat related to the suction force at the Ryukyu Trench. As a function of these two forces, the stress regime rapidly changes from south to north, from compression in the Taiwan collision zone to extension in the Ryukyu subduction zone. By using a two-dimensional plane-stress finite-element model with elasto-plastic rheologies, we analyze the relationship between the kinematics of convergence, the crustal deformation, and the stress distribution in the present Taiwan collision zone between the Ryukyu and Luzon subduction zones. Our model predicts that in northeastern Taiwan, a transition zone may develop between pure compression (which characterizes most of the collision zone of Taiwan) and pure extension (which prevails in the northeastern part of the model). The transition in the stress field is characterized by two intermediate regimes, one mainly compressional and one mainly extensional, where significant strike-slip deformation is expected. We show that the interaction between the opening of the Okinawa Trough and the collision at the northwestern boundary of the Philippine Sea plate plays a crucial role in controlling the stress and strain patterns. The location of the transition zone in the north is a balance between these two factors, which may explain the variability of tectonic regimes in the region. Hu, J.-C., Yu, S.-B., Chu, H.-T., and Angelier, J., 2002, Transition tectonics of northern Taiwan induced by convergence and trench retreat, in Byrne, T.B., and Liu, C.-S., eds., Geology and Geophysics of an Arc-Continent collision, Taiwan, Republic of China: Boulder, Colorado, Geological Society of America Special Paper 358, p. 149–162. INTRODUCTION The island of Taiwan is located at the junction of the Ryukyu arc and the Luzon arc at the western edge of the Philippine Sea plate. The plate interaction around this segment of the convergent plate boundary between the Eurasian and Philippine Sea plates is complex (Fig. 1). Seismicity northeast of Taiwan indicates the presence of a Wadati-Benioff zone, where the Philippine Sea plate subducts northward along the Ryukyu Trench (e.g., Tsai, 1986). In contrast, south of Taiwan, the Eurasian plate subducts southeastward beneath the Philippine Sea plate along the Manila Trench (e.g., Wu, 1978; Tsai, 1986; Pezzopane