ANALOG MODELING THE SUBDUCTION OF THE CHINESE CONTINENTAL MARGIN FRACTURE ZONE PROMONTORY IN WESTERN TAIWAN

Taiwan is the product of the propagation of an orogenic system by partial subduction and the oblique collision of the Eurasian Plate (EP) with the Philippine Sea Plate (PSP). The direction of subduction flips underneath Taiwan, as the PSP begins to subduct beneath the EP in northern Taiwan. The location of this switch point approximately corresponds with the location of a hypothesized southeast-pointing angular promontory of continental crust bounded by a continental margin fracture zone and rift basin normal faults on the EP. Prior research has analyzed seismic data, magnetic data, GPS vectors, structure and geomorphologic features to identify and constrain the location of the promontory. The research suggests it is bounded by the NE-trending continental margin magnetic anomaly (CMMA) and in the north by a NNW-trending topographic break and the Sanyi-Puli seismic zone. The goal of our work is to utilize analog modeling to contribute to the analysis of the promontory. We focus on creating a model for the promontory and surrounding area that is geometrically, kinematically, and dynamically scaled in order to generate velocity fields and topographic images. To accomplish this, a mechanical hand-crank sandbox modeled after the experiments described in Davis's discussion of critical taper theory has been modified to be operated by a computer-controlled stepper motor and a high-resolution camera has been carefully adjusted to take photos at fixed intervals for use in Particle Image Velicometry (PIV) analysis. Preliminary results suggest a good correlation with real world data, thus providing additional evidence for the existence of the promontory as described in previous research.