Imaging spatiotemporal evolution of postseismic deformation of the 2003 M6.8 Chengkung earthquake

Abstract:

Large earthquakes are usually accompanied by rapid afterslip postseismic deformation. It is important to understand how much slip occurs and how slip migrates after the earthquakes. M6.8 Chengkung earthquake is one of largest earthquakes in Taiwan in recent years. Previous studies estimate accumulative afterslip distribution from 3 to 6 months after the main shock. However, the inferred slip distributions are inconsistent. Here we analyze the postseismic slip evolution of the Chengkung earthquake by using time series from about 40 stations. The GPS data are from the Taiwan GPS website service of the Taiwan earthquake research center. We first fit secular velocity, antenna changes, coseismic displacements, and a presumed logarithmical pattern to each GPS time series by using a MCMC metropolis algorithm. Then we remove secular velocity and instantaneous signal offsets from the time series. In addition, we construct 3D fault geometry based on relocated ambient seismicity and regional tomography. We use a modified Network Inverse Filter to estimate spatiotemporal slip migration directly from GPS time series. This method can allow temporal smoothing parameter changes and simultaneously solve for slip and common model errors. With this method, we can imagine spatiotemporal slip evolution of afterslip postseismic deformation.