汶川地震科学钻探2号孔(WFSD-2)随钻泥浆氢和汞浓度与断裂构造关系

Relationship between concentrations of hydrogen and mercury of No.2 hole cores at the Wenchuan Earthquake Scientific Drilling and fault zone structure

以WFSD-2钻孔为研究对象,分析了随钻泥浆氢(H_2)和汞(Hg)浓度特征,在垂向上存在显著不均匀性,出现多段浓度异常高值.研究表明:(1)H_2和Hg浓度异常与次级断裂和岩石构造性质有较大关系,以断裂带或破碎带为通道运移而产生高值异常;(2)随钻泥浆H_2和Hg浓度特征暗示了汶川地震WFSD-2孔中主滑移带位置,表明随钻流体特征是识别地下裂隙带、破碎带或断裂带的途径之一;(3)H_2和Hg浓度异常还可能与构造块体边界强震活动和断裂带近场中等地震活动有关.本文研究结果为分析大震过程中深部流体活动行为提供了H_2和Hg地球化学特征依据,对地震前兆机理研究也具有重要的参考价值.

Taking the WFSD-2 drill hole as the research object,we analyzed the characteristics of hydrogen（H_2）and mercury（Hg）concentrations in the drilling mud.In the vertical direction,there was significant non-uniformity,and there were multiple sections of abnormally high values.The research shows that（1）the abnormal concentrations of H_2 and Hg have a notable relationship with secondary faults and the properties of rock structure,and high-value anomalies are caused by the channel migration of fault zones or fractured zones.（2）The characteristics of H_2 and Hg concentrationsin the mud collected while drilling indicate the position of the main slip zone in the WFSD-2 drilling of the Wenchuan earthquake,implying that the study on the characteristics of the mud fluid collected while drilling is one of the approaches to identify underground fissure zones,fractured zones or fault zones.（3）Abnormal concentrations of H_2 and Hg may also be related to strong seismic activity at the boundary of the tectonic block and moderate seismic activity in the near-field of the fault zone.The results of this study provide evidence on geochemical characteristics of H_2 and Hg for the analysis of deep fluid activity during large earthquakes,and also serve as an important reference for the study on the mechanism of earthquake precursors.