Correlation Between Fault Movement and Seismic Activity in Northern Tibetan-Plateau: a Case Study from Numerical Simulation

In the northern Qinghai-Tibet Plateau, active areas of Ms ≥ 6 earthquakes are mostly located on special tectonic parts of faults, for instance fault bends. The frequent occurrence of strong earthquakes in local regions is inevitably related to the morphology of the faults themselves, the long-term state of fault motion and the accumulation of stress. Previous studies of their interrelationships have mostly been based on ideal or simple fault models. We developed a three-dimensional viscoelastic finite element model with a refined geometry of major faults to calculate long-term steady-state fault slip rates, fault stress accumulation rates and regional stress fields in this region, using GPS velocity data as boundary conditions. The kinematic and stress characteristics of the fault bend parts and the dynamical background of the strong seismic activity in these parts are discussed. The results indicate that active areas of moderate-strong earthquakes have a background of high stress accumulation. The slip rate and stress accumulation rate of faults are non-uniform along the fault strike. Stress accumulation rates are high at fault bends with moderate-strong seismic activity, but slip rates tend to be low at bends or differ significantly between fault segments on either side of the bends, suggesting that movement between different fault segments is not coordinated. Meanwhile, the maximum shear stress results show that the shear stress accumulation rate is higher in the active region of strong earthquakes. The high stress accumulation on and near the seismogenic fault and uncoordinated movements between adjacent fault segments are important dynamic factors that cause moderate-strong earthquakes to cluster on and near the bends. Therefore, special tectonic parts such as fault bends are effective in controlling the slip rate, stress accumulation and seismicity of faults, which are potential seismogenic areas of strong earthquakes.