研究期間：10108~10207;The rheology of viscously deforming rocks at depth is of fundamental importance when trying to understand stress evolution of the earthquake cycle and therefore time-dependent seismic hazard along active faults. Large crustal earthquakes are assumed to generate co-seismic stresses in the ductile part of the lithosphere, where materials are too weak to sustain long-term shear stresses but tend to release them over decades following the earthquakes. Strains caused by the post-seismic stress relaxation are in turn transferred through the elastic upper crust, producing observable transient deformation on the surface that has been used to infer the rheology of the continental crust and upper mantle. This research project tends to use geodetic measurements (leveling, GPS, and InSAR) of postseismic deformation following the 1999 Mw 7.6 Chi-Chi earthquake, together with other geophysical constraints such as seismic, gravity, and heat flow observations, to study the lithospheric rheology of the Taiwan area. Two semi-analytic Maxwell viscoelastic modeling methods (1-D and 2-D) and power-law rheology of non-Newtonian flow will be employed to evaluate the lithospheric rheologic structure based on time-dependent changes in crustal motion determined by geodetic measurements. A finite element modeling method (Pylith) would also be tested to evaluate the stress evolution due to viscoelastic relaxation of the lithosphere, and its relation to earthquake cycle based on the time history of paleoearthquakes of the Taiwan area will also be addresses. The results of this study can shed light on the dynamic processes of arc-continent collision and mountain building and recurrence models of large earthquakes in the Taiwan area.
