The vertical postseismic deformation following the 2004 Parkfield earthquake

Studies have shown that the postseismic transient following the 2004 Parkfield earthquake is dominated by aftersllip. However, the studies are mainly focus on the horizontal deformation and ignore the vertical deformation. The focus of this study is the postseismic deformion in vertical caused by 2004 event. We examine the time series of 20 near San Andreas fault CGPS stations in the vicinity of the Parkfield segment to infer the time-dependent postseismic slip. We firstly use the time series to derive an afterslip distribution model for the Parkfield earthquake using only horizontal components, and compare the model’s agreement with the measured vertical deformation. The results show the migration of groundwater is the main reason for the vertical postseismic deformation.