A thin-skinned collisional model for the Taiwan orogeny

The thin-skinned tectonics model was often used for the collision orogeny of Taiwan. However, the suture zone of collision and faulting were not included in that model. It is not convenient for understanding the pattern of the plate collision around Taiwan and the contributions of collision and faulting to the mountain building. Moreover, the results obtained from the thin-skinned tectonics model cannot be compared with the GPS (Global Positioning System) data across the suture zone of collision. Based on a number of recent studies, we present a different model, called the thin-skinned collisional model, for the Taiwan orogeny as an attempt at solving the problems mentioned above. The model differs from the existing thin-skinned tectonics model for Taiwan mainly in that it has included the suture zone of the plate collision and faulting in the thin-skinned block, and thus enables us to probe into the collision pattern and to compare it with the GPS data. Several arguments are put forward to support this model. The model is theoretically tested by the use of the elasto-plastic finite-element method. From the computed results we find that the model fits the observation data well, for they can reproduce the velocity distribution measured by GPS and the major topography features of Taiwan. In particular, the computed results suggest, at least theoritically, that the Longitudinal Valley of eastern Taiwan would be a ramp valley and its western boundary fault would be the collision boundary between the Eurasian plate and the Philippine Sea plate. Taking the theoretical results into account, a new type of plate convergence boundary in the Longitudinal Valley area could emerge from the thin-skinned collisional model.