Comparison of groundwater-level response to near earthquake and distant earthquake: taking wenchuan earthquake and Sumatra earthquake for example

Seismic groundwater level anomalies caused by earthquakes are characterized by diversity and complexity. To further explore the mechanism between deep groundwater dynamics and seismic activity and to play an indicative role of groundwater-level to seismic activity, taking 2008 Wenchuan Ms8.0 earthquake and 2007 Sumatra earthquake Ms8.5 as case study, by the analysis of groundwater-level in the regions including Sichuan, Yunnan, Gansu, Shaanxi, Chongqing, the study summed up the different response characteristics and regularity of the same well water level to the two earthquakes. Groundwater level response characteristics to distant earthquake mainly appeared oscillation-type and step-type, the occurrence of anomalies was later than the earthquake. Groundwater-level response characteristics to local earthquake was relatively complicated, mainly appearing step, pulse and oscillation types, and the occurrence of anomalies was as almost simultaneous with earthquake. And according to the response mechanism of groundwater-level to crustal stress, the authors analyzed the different response reasons of typical well water levels to distant and local earthquakes. The groundwater-level response to distant earthquake is due to the seismic wave stress on the aquifer medium. The groundwater-level response to local earthquake is mainly due to the regional tectonic stress and the seismic wave stress on the aquifer medium. The smaller the epicenter distance is, the greater the seismic tectonic stress field under the aquifers is.