Thermal modeling of continental subduction and exhumation constrained by heat flow and seismicity in Taiwan

The thermal evolution of crustal exhumation subsequent to the subduction of the continental margin is modeled through numerical solutions to the two-dimensional heat conduction equation. The boundary conditions used in the modeling are basically constrained by available geophysical and geological observations in the Taiwan area. Temperature distributions are calculated at one-million-year intervals over a 5 Ma duration. Although this study presents a tentative estimation based on some reasonable assumptions, the preliminary results not only explain the sharp change in seismicity within the crust but also agree with the general heat flow pattern on the surface of Taiwan. More specifically, both the high heat flow and the aseismic belt beneath the Eastern Central Range, which are probably attributed to higher temperatures within the crust, are modeled by crustal exhumation after the subduction of the continental margin. However, the occurrence of deeper earthquakes east of the Central Range is a result of the lower thermal gradient, which is due to the subduction of the cold continental crust into the uppermost mantle. In summary, preliminary thermal modeling supports the possibility of a tectonic model of active continental subduction and crustal exhumation for the Taiwan Orogen. (C) 2000 Elsevier Science B.V. All rights reserved.