断裂带土壤气测量方法在断层活动性研究中的应用——以嘉峪关断层为例

The application of measurement method of soil gas from fault zone to fault activity study:A case study of Jiayuguan fault

为了判断甘肃省嘉峪关断层监测点气氡浓度2015年6月以来的高值异常变化是否反映了嘉峪关断层活动的增强,本文基于土壤气跨断层分布规律,应用跨断层测量方法,通过多组分相关性分析及理论建模,综合分析了嘉峪关断层监测点气氡浓度高值异常变化与断层活动的关系。结果显示:监测点断层气中氡浓度快速增加期间,CO2、CH4和H2的浓度没有增加,气氡与CO2、CH4浓度的变化不具正相关关系,表明监测点增加的氡气来源深部较浅,不代表断层活动的增强。监测点两侧跨断层测量结果表明,地表环境未改变一侧的氡气浓度符合断层气分布规律,地表环境发生改变一侧的氡气浓度不符合断层气分布规律,并且地表环境的改变时间与监测点气氡浓度异常变化时间同步。因此监测点气氡浓度的高值异常是由地表环境的改变引起的,嘉峪关断层的活动并没有增强。该方法为用断裂带土壤气体测量方法研究断层活动性的可靠性提供了思路。

In order to determine whether the increase of gas radon concentrations at the monitoring point of the Jiayuguan fault since June 2015 can reflect the stronger activity of the Jiayuguan fault or not,the authors applied the cross-fault measurement method based on the typical distribution pattern of soil gas across faults and analyzed comprehensively the relationship between the abnormal changes of gas radon concentrations and the fault activity through multi-component correlation analyzing and theoretical modeling.The results show that the concentrations of CO2,CH4,and H2 from the same monitoring point do not increase during the rapid increase of the gas radon concentrations from the monitoring point of the fault.There is no positive correlation between them.The adding of gas radon concentration does not come from deep crust and it does not mean the stronger activity of the Jiayuguan fault.The results of the gas radon measurement across faults which lie on both sides of the monitoring point show that the gas radon concentrations are different,and this is consistent with the typical distribution pattern of fault gas on the unchanged side of the surface environment but it does not conform to the typical distribution pattern of fault gas on the changed side of the surface environment.The increase of gas radon concentrations is correspondingly with the change of the surface environment in time.Therefore,the increase of gas radon concentration at the fault monitoring point is caused by the change of the surface environment,and the activity of the Jiayuguan fault does not increase.This method provides a thinking for the improvement of reliability in using fault soil gas to judge fault activity.