临潭—宕昌断裂带跨断层土壤气地球化学空间分布特征研究

Geochemical spatial distribution characteristics of soil gas along the Lintan-Tanchang fault zone

活动断裂带气体地球化学空间分布特征分析是区域构造和断裂活动性分区(分段)及其地震危险性分析的重要方法之一。通过临潭—宕昌断裂带9条测线剖面的土壤气Hg、Rn浓度观测,结合断裂带分段活动特性与大地热流背景数据,开展不同分段气体浓度空间分布特征分析,深入探讨土壤气地球化学空间分布的特征及成因。结果表明:断层土壤气在临潭—宕昌断裂带具有明显的分段特征,根据其活动特性可将断裂带分为东、西两段,且断层土壤气地球化学空间分布与大地热流和地震活动之间存在良好的相关关系;在断裂西段高热流区域,中强地震频发,但小震活动较弱,Hg、Rn浓度强度较低;东段低热流区域,中强地震较少,但小震活动活跃,Hg、Rn浓度强度较高。研究结果作为区域地球化学背景特征,可为今后地下流体异常活动分析提供重要依据,对进一步跟踪未来可能发生地震的断层及其活动段具有重要意义。

The study on geochemical spatial distribution characteristics of gas along the fault zone is an important method for analyzing the regional structure,activity segmentation,and seismic risk of the fault.In this study,we took the Lintan—Tanchang fault zone as study area and observed the soil gas Hg and Rn concentrations in 9 survey lines.We analyzed the spatial distribution characteristics of gas concentration in different fault sections by combining the characteristics of fault activity and the heat flow density.The study show results that the Lintan—Tanchang fault zone has obvious segmentation features.Base on the fault activity characteristics,the Lintan—Tanchang fault could be divided into two segments:east and west.And the spatial distribution of soil gas geochemistry is correlated with heat flow and seismic activity;The western section of the fault is an area of high heat flow,and strong seismic occur frequently in this section,but small seismic activity is weak,with lower Hg and Rn concentration intensity.While in areas with lower heat flow in eastern segment of fault,there are fewer strong seismic but intense small seismic activity,with higher Hg and Rn concentrations intensity.This study provides evidence of subsurface fluid activity in the study area,which is vital in tracing the faults and active segments with seismic risk.