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Title:: Fluid Anomalies Detection of the Dian-17 Well Based on Geochemical Analysis and its Application

Author(s):: TIAN Lei; YU Huaizhong; ZHOU Zhihua; (China Earthquake Networks Center,Beijing 100045,China)

Keywords:: the Dian-17 observation well; geochemistry; hydrogen and oxygen isotopes; second order differential acceleration; corresponding relation to earthquakes

摘要:: 以滇17井的水化学观测项为例,分析该观测井周边水文地质及水文地球化学情况,确定含水层性质及其与周边水体的补给关系,通过二阶差分方法,确定观测数据二阶差分结果的异常波动,提取相关信息。结果表明:观测含水层与周边大型地表水体及浅层地下水等不存在直接水力联系,观测数据的变化反应了含水层的整体变化,其变化的主要原因是地下应力环境改变。二阶差分方法处理结果显示:相对于无震期间的数据变化,Ca²⁺,Mg²⁺,HCO^-₃的二阶差分结果在观测井周边200 km内5～5.9级地震、300 km内6～6.9级地震及500 km内7级以上地震发生时段会出现明显波动,并伴随有高值突跳。这一研究结果表明在明确含水层性质的前提下,使用二阶差分方法能够直观反应区域应力变化,为地震趋势判定提供依据。

Abstract:: Taking hydrochemical observation items in Dian-17 well as an example,we identified the hydrogeological and geochemical condition around the observation well and determined the nature of aquifer and its recharge relationship with surrounding water bodies. By means of the two order difference method,we determined the abnormal fluctuation of the two order differential result of the data,and extracted the relevant information. There is no direct hydraulic connection between the aquifer and other possible disturbance sources,such as large surface water bodies and shallow groundwater. The change of observation data reflects the overall change of the whole aquifer,whose main reason might be the change of enviorment of tectonic stress.The result of the second order differential acceleration shows that calcium,magnesium and bicarbonate monitoring data have a high-frequency fluctuation and high value kicks before some M5 earthquakes within 200 km,M6 earthquakes within 300 km,and M7 earthquakes within 500 km from the epicentre. This research shows that the second order differential acceleration result is an evidence of the increasing tectonic stress on the premise of confirming the condition of the observation well,and can be a support for the earthquake prediction.