Complexity of the coseismic rupture for 1999 Chi-Chi Earthquake (Taiwan) from inversion of GPS observations

Based on the elastic half-space model and the layered-earth model, we use Global Position System observations to invert the distribution of coseismic slip along the Chi-Chi earthquake rupture. Bending fault planes are introduced in our models. The results indicate that the shear slip model can not fit horizontal and vertical coseismic displacements simultaneously, unless the fault-normal motion (tensile component) is considered in the inversion. We interpret that the fault-normal motion reflects the “roughness” of fault planes, demonstrating the complexity of the rupture in property and geometry. The distribution of the fault-normal motion appropriately fits with the complexity of surface coseismic rupture from the field investigation, and the distribution of the strike-dip slip of coseismic rupture is similar to the results from inversion of the teleseismic data.