IMPACT OF BASEMENT HIGH ON THE STRUCTURE AND KINEMATICS OF THE WESTERN TAIWAN THRUST WEDGE - INSIGHTS FROM SANDBOX MODELS

Experimental modeling allows description of the development and kinema tics of structures in mountain belts formed during oblique convergence . In the collision geometry of the Taiwan mountain belt, the Chinese c ontinental margin is oriented about N60 degrees E, whereas the N16 deg rees E Philippine Sea plate backstop is moving toward the Eurasian pla te in a N55 degrees W direction. In addition to this oblique convergen ce mechanism, most of the foreland structures are strongly influenced by the shape of the backstop and structural highs. Sandbox experiments have been conducted to simulate the neotectonics of western Taiwan, T he kinematics of deformation comprises a combination of compression an d rotation, which results in a local partitioning between thrusting an d strike-slip movements. The results of specific analog models demonst rated that: (1) most of the tableland structures in the western Taiwan , such as the Tatu, Pakua, Chungchou and Chia-Yi tablelands can be int erpreted as a hinge part of drag anticline formed by fault-propagating fold process; (2) most of the basin and plain structures in the weste rn Taiwan, such as Taichung and Chianan basins, can be interpreted as a part of piggy back basins; (3) the frontal thrust may have the first appearance of rupture in front of and between the Peikang high and th e Kuanyin high; (4) NW trending link faults may be developing within t he transfer zones; and (5) an escape structure formed to the south of the Peikang high can be correlated with bathymetric map and models.