The preliminary crustal conductivity anomaly from MT data in Taiwan

Taiwan is located in a complex tectonically active region where the Philippine Sea plate is subducting northwestward along the Ryukyu Tenth while the Eurasia plate is subducting eastward along the Manila Trench. The magnetotelluric method (MT) was used as a part of an integrated project to map this intricate tectonic problem. Nineteen MT soundings, arranged uniformly covering the entire Taiwan, were conducted and analyzed to map the 3-D resistivity structures beneath Taiwan. Results show the existence of a distinct conductive zone located beneath the Central Range in the uppercrust of central Taiwan. This zone is not only consistent with the surface distributions of the hot springs in Taiwan, but also matched with the low velocity zone in Taiwan. We infer that the main cause of this crustal conductivity anomaly might have resulted from the heat accutnulated fro in crustal metamorphsm, and from the heat intrusion from the oceanic upper mantle of the Philippine Sea plate, which has been colliding with the Eurasian plate.