地下水位对近震和远震异常响应的比较——以汶川地震和苏门答腊地震为例

Comparison of Groundwater-Level Response to Near Earthquake and Distant Earthquake:Taking Wenchuan Earthquake and Sumatra Earthquake for Example

地震引起的深层地下水位异常具有多样性和复杂性的特点。为了进一步探索深层地下水位动态与地震作用过程之间的联系机制,发挥深层地下水位对地震活动的指示作用,以2008年汶川Ms8.0地震和2007年苏门答腊Ms8.5地震为研究背景,对川、滇、陕、甘、渝地区井水位对两次地震的响应特征进行了比较。研究发现:地下水位远震响应形态主要以振荡型和阶变型为主,异常出现的时间较晚;地下水位近震响应形态比较复杂,以阶变型、脉冲型以及振荡型为主,异常出现的时间几乎与地震的发生同步。根据深层地下水位对地壳应力的响应机理,分析了各典型井水位对远震和近震不同响应的原因。结果表明:地下水位对远震的响应主要是由于含水层介质受到地震波应力的作用;对近震异常响应原因比较复杂,主要是含水层介质受到区域构造应力和地震波应力的共同作用的结果,震中距越小,含水层受到震源构造应力场的控制作用越大。

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.