The Chi-Chi earthquake, after 10 years of study, is arguably the one of the best constrained and best studied large thrust-belt earthquake worldwide, considered from a number of perspectives, including geophysical instrumentation, strong ground-motion records, geodetic constraints on surface displacements, post-earthquake borehole data and surface geologic studies. In addition it is arguably the geologically best constrained earthquake from the point of view of independent constraints on the 3D subsurface structural geometry of the Chelungpu and related faults that slipped in the earthquake, as well as the deeper tectonic structure of Taiwan that feeds lithospheric convergence into the Chelungpu fault system. These insights from the Chi-Chi earthquake may give us some ideas for study of the structural geology of the Wenchuan earthquake. Both are thrust-belt earthquakes, but the Wenchuan is in a more interior and more complex position, making it more challenging to study. Here we present the 3-D structural geometry of the key faults in the Chi-Chi earthquake and show how they are related to the coseismic surface and fault displacements. We then make comparisons to the coseismic displacements in the Wenchuan earthquake and their relationship to structural geometry The Chi-Chi earthquake, after 10 years of study, is arguably the one of the best constrained and best studied large thrust-belt earthquake worldwide, considered from a number of perspectives, including geophysical instrumentation, strong ground-motion records, geodetic constraints on surface displacements, post-earthquake borehole data and surface geologic studies. In addition it is arguably the geologically best constrained earthquake from the point of view of independent constraints on the 3D subsurface structural geometry of the Chelungpu and related faults that slipped in the earthquake, as well as the deeper tectonic structure of Taiwan that feeds lithospheric convergence into the Chelungpu fault system. These insights from the Chi-Chi earthquake may give us some ideas for study of the structural geology of the Wenchuan earthquake. Both are thrust-belt earthquakes, but the Wenchuan is in a more interior and more complex position, making it more challenging to study. Here we presen t the 3-D structural geometry of the key faults in the Chi-Chi earthquake and show how they are related to the coseismic surface and fault displacements. We then make comparisons to the coseismic displacements in the Wenchuan earthquake and their relationship to structural geometry