| Summary: | 碩士 === 國立中正大學 === 地震研究所 === 102 === We have conducted numerical modeling to test the hypothesis of Eurasian slab breakoff in response to the fast uplift in Northern Taiwan. Previous studies suggested that the southern part of the Hsuehshan Range had a low horizontal shortening rate yet a high uplift rate during last 1Ma. Recent seismic tomography studies also implied part of the Eurasian plate may have been torn apart in this area. We suspect the southward rollback of the Philippine Sea Plate is responsible for the slab breakoff. Our preliminary simulation results show that slab breakoff in this area might not be spontaneous. Instead, it may be induced by southward rollback of the Philippine Sea Plate corresponding to the opening of the Okinawa Trough. The retreating Philippine slab exerts an additional force upon the underlying Eurasian Plate. This additional force has been tearing the Eurasian Plate apart and resulting in subsidence of the northern part of the Hsuehshan Range. However, before the slab breakoff, our models show that the loading by the rollback of the Philippine Sea Plate would compress the Eurasian continental lower crust to form crustal-scale reverse faults, which leads to fast uplift analogous to what observed at the southern part of the Hsuehshan Range.
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