Three-dimensional modeling of interseismic, co-seismic, and post-seismic deformation in Taiwan

California Institute Of Technology, Pasadena CA

Investigators

Abstract

Currently, crustal dynamics lacks internally consistent continuum models that explain observations spanning the entire earthquake cycle including, the interseismic, coseismic, and postseismic periods, while being consistent with the longer timescale strain manifest in the geology, such as the distribution of topographic relief. Studies of the earthquake cycle in Taiwan are somewhat unique because of the high strain rates over all three phases of the earthquake cycle and the extraordinary geodetic coverage before, during, and after the 1999 Mw 7.6 Chi-Chi earthquake. In addition the geometry of the primary faults structures is now relatively well known and reasonably reliable estimates of 3D variations in material properties are becoming available. Our effort aims to build a single model that addresses both the misfits of existing models to their respective data sets, while at the same time trying to derive an internally consistent description that works up to time scales involving the building of the mountains. We are addressing the following tasks in approximately this order: 1) Revise elastic coseismic and afterslip models for the 1999 Mw 7.6 Chi-Chi earthquake using 3D elastic structures and a new fault geometry. These models will consider all available GPS, SAR, and optical geodetic data. 2) Construct an initial suite of 2-D visco-elasto-plastic models to develop intuition for spin-up issues, as well as effects of different boundary conditions. 3) Construct 3D post-seismic and interseismic visco-elasto-plastic models. 4) Consider observationally constrained thermal controls on rheology - as well as the role of erosion in modifying the long-term evolution of mountain range. This projects aims to develop an internally consistent geodynamic model spanning time scales from earthquakes up to that of mountain building. It takes advantage of, and contributes to, state-of-the-art geodetic and modeling tools to address the inherently difficult problem of laterally varying rheological structures both on major faults and in the surrounding media. All analysis tools being developed as part of this project are released to the public. This activity forms part of a larger collaboration with scientists in the U.S. and Taiwan. We expect that this effort will result in a better understanding of seismic potential in Taiwan.