胡宁,马志敏,娄露玲,王宇,张宝山,王明亮,陈蒙,郭德科. 2022. 汤阴地堑南部土壤Rn空间分布特征. 地震学报,44(3):489−500. doi: 10.11939/jass.20200054
引用本文: 胡宁,马志敏,娄露玲,王宇,张宝山,王明亮,陈蒙,郭德科. 2022. 汤阴地堑南部土壤Rn空间分布特征. 地震学报,44(3):489−500. doi: 10.11939/jass.20200054
Hu N,Ma Z M,Lou L L,Wang Y,Zhang B S,Wang M L,Chen M,Guo D K. 2022. Spatial distribution characteristics of soil radon in the southern Tangyin graben. Acta Seismologica Sinica44(3):489−500. doi: 10.11939/jass.20200054
Citation: Hu N,Ma Z M,Lou L L,Wang Y,Zhang B S,Wang M L,Chen M,Guo D K. 2022. Spatial distribution characteristics of soil radon in the southern Tangyin graben. Acta Seismologica Sinica44(3):489−500. doi: 10.11939/jass.20200054

汤阴地堑南部土壤Rn空间分布特征

Spatial distribution characteristics of soil radon in the southern Tangyin graben

  • 摘要: 为分析汤阴地堑南部土壤Rn空间分布特征,揭示其与断裂构造、岩性及沉积层厚度之间的联系,本文采用网格化布点野外流动观测方法测定了该地区380个点的土壤Rn浓度,结果表明:汤阴地堑土壤Rn浓度介于3.09—78.54 kBq/m3,背景均值为27.22 kBq/m3,异常阈值下限为48.40 kBq/m3。在空间分布上,研究区西部(以第四系等厚线50 m为界),受岩石单元和人类石料开采活动的影响,Rn浓度背景值高于东部。在西部高浓度背景影响下,Rn浓度高值异常点除沿汤西断裂带分布外,还沿断裂带外围呈斑块状分布,断裂带对气体释放的控制作用在一定程度上被掩盖。而东部地区,覆盖层较厚,Rn浓度背景值较低,部分高值异常点主要沿汤中和汤东断裂带分布,显示出构造对气体迁移的控制作用;另一部分高值异常点与第四系等厚线近似平行,呈条带分布,推测新乡—卫辉间存在一条规模较大的隐伏断裂。此外,研究区主要断裂带的Rn异常衬度表现为汤东断裂带高于汤西和汤中断裂带。结合研究区地质背景和深部孕震环境认为,该Rn异常衬度表现是汤阴地堑南部构造活动背景的反映。因此,研究区土壤Rn浓度空间分布主要受断裂构造、岩性、沉积层厚度以及人类活动的影响,气体异常衬度主要受汤阴地堑南部构造活动背景的控制。土壤Rn浓度能够有效地用于汤东活动断裂带的构造活动监测,而对位于隆起区与沉降区的过渡地带、断裂局部出露于地表,且受人类活动影响较大的汤西断裂带则需充分考虑环境背景的影响。

     

    Abstract: This paper discussed the spatial distribution characteristics of radon in the soil gas and their relationship with faults, geological structures, lithology, and sediment thickness based on the radon concentrations obtained by the field mobile measurement at the gridding layout observation points in the southern Tangyin graben. The measurements showed that the soil radon concentrations in the Tangyin graben varied from 3.09 to 78.54 kBq/m3 with a mean value of 27.22 kBq/m3, and the anomalous threshold was 48.40 kBq/m3. Spatially, the studied area was divided into two parts based on the contour of Quaternary system (50 m thickness), the distribution characteristics of soil gas presented that radon background concentrations were higher in western region than that in eastern evidently because of the difference of lithology units made up the local strata and the influence of human mining activity. Accordingly, the radon concentration anomalies of soil gas in western region were patchily scattered on the periphery of Tangxi fault belt besides of distributed along the fault belt itself. Nevertheless, in eastern region, the most of radon concentration anomalies mainly presented along Tangzhong and Tangdong fault belts. Similarly, the contours map of radon concentrations also indicated the azimuth of concentration anomalous belts were consistent with the strike of Tangzhong and Tangdong faults in east region, which implied the emanation of deep-seated source gas was controlled by fault structures. In addition, the radon concentrations contours map also suggested there was a radon anomalous band of NE strike that was almost parallel to contours of local Quaternary system thickness, by which we speculated there was a buried fault. Furthermore, in this studied area, though the release intensity of soil radon in the western part was significantly higher than that in the middle-eastern part, the radon concentrations anomalous extent showed a trend of increasing from west to east, which revealed that the Tangdong fault was more active than others. The comprehensive analysis indicated that the spatial distribution of soil radon concentrations was mainly controlled by fault structures, lithology formation, thickness of sedimentary layer, and human mining activities, and variations of radon concentrations were mainly dominated by the background tectonic activity of southern Tangyin graben. Our results imply that soil radon is an effective indicator for tectonic activity observation of Tangdong fault. While it is appiled to Tangxi fault which is located in the transition region between the uplift and the subsidence the influence of environmental background needs to be fully considered, because of the impact of bedrock cropping out partially and human mining activities.

     

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