Temporal Variation and Spatial Distribution of Groundwater Level Changes Induced by Large Earthquakes

Sustained coseismic changes in groundwater level due to static strain during earthquakes could be considered as an indicator of crustal deformation. These usually occur abruptly but recover slowly after earthquakes. High-frequency data indicate a time lag between the change well water levels and that aquifer. Abnormal post-seismic were observed, possibly caused by cross-formation flow, fracturing, or relief. Although sustained are generally induced local earthquake, they also triggered distant large earthquake has occurred at same tectonic plate. The magnitude polarity may vary wells different depths multiple-well stations, revealing additional information about complexity deformation subsurface. Coseismic falls dominated near ruptured seismogenic fault 1999 M7.6 which implied extension adjacent thrust fault. However, rises prevail most areas, suggesting compression plate convergence plays major role on island Taiwan