地震地质 ›› 2024, Vol. 46 ›› Issue (2): 433-448.DOI: 10.3969/j.issn.0253-4967.2024.02.011

• 研究论文 • 上一篇    下一篇

平原M5.5地震土壤气地球化学特征及成因

苏淑娟1,2)(), 陈其峰1),*(), 孙豪1), 刘军1), 冯梁乐1), 徐继龙1), 杨彦明3,4), 雒昆利2)   

  1. 1) 山东省地震局, 济南 250000
    2) 中国科学院地理科学与资源研究所, 北京 100101
    3) 内蒙古自治区地震局, 呼和浩特 010010
    4) 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029
  • 收稿日期:2023-11-01 修回日期:2023-12-27 出版日期:2024-04-20 发布日期:2024-05-29
  • 通讯作者: *陈其峰, 男, 1974年生, 高级工程师, 主要从事地震流体地球化学研究, E-mail: qifeng1974@163.com
  • 作者简介:

    苏淑娟, 女, 1979年生, 2006年于山西师范大学获自然地理学专业硕士学位, 高级工程师, 现主要从事地震流体地球化学研究, E-mail:

  • 基金资助:
    山东省地震局一般科研项目(YB2416); 山东省地震局一般科研项目(YB2313); 中国地震局震情跟踪定向工作任务(2024020302); 国家自然科学基金(42277196); 国家自然科学基金(41877299); 内蒙古自治区自然科学基金(2023MS04012)

GEOCHEMICAL CHARACTERISTICS AND GENESIS OF SOIL GAS IN THE PINGYUAN M5.5 EARTHQUAKE

SU Shu-juan1,2)(), CHEN Qi-feng1),*(), SUN Hao1), LIU Jun1), FENG Liang-le1), XU Ji-long1), YANG Yan-ming3,4), LUO Kun-li2)   

  1. 1) Shandong Earthquake Agency, Jinan 250000, China
    2) Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
    3) Earthquake Agency of Inner Mongolia Autonomous Region, Hohhot 010010, China
    4) State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2023-11-01 Revised:2023-12-27 Online:2024-04-20 Published:2024-05-29

摘要:

2023年8月6日2时33分, 山东省德州市平原县发生M5.5地震。文中跨震中布设4条长30km的勘测线, 现场测量了土壤气Rn、 CO2和Hg浓度。结果表明: 1)土壤气浓度表现出明显的空间差异, 震中区与4条测线的东、 西两端气体浓度相对较高。2)土壤气浓度的空间分布特征在震中及其东部地区相似, 但在震中西部差异较大, 在西部旧城断裂(F3)附近, Rn和CO2的浓度高于震中区, 推测应与地震活动和F3控制的鼻状构造有关。3)Rn、 CO2和Hg的浓度在陵县-冠县断裂(F1)和F3附近出现高值异常, 余震自F1向F3发展, 结合地质与地球物理研究资料推断, 平原M5.5地震应与F1和F3共同作用有关。以上结果表明, 气体地球化学方法能较好地指示隐伏断层的位置与展布方向。

关键词: 平原M5.5地震, 断层土壤气浓度, 陵县-冠县断裂, 旧城断裂, 构造地球化学

Abstract:

At 2:33 am on August 6, 2023, a M5.5 earthquake occurred in Pingyuan county, Dezhou city, Shandong Province. The faults within the epicenter and adjacent areas are deeply buried by the thick Quaternary sediment cover on which human activity is intensive, which makes it difficult to determine the location of the buried active faults from the surface based on geological and geomorphological evidences. It is necessary to detect the location of the buried active faults around earthquake areas and estimate their seismic risk.

In this study, based on the epicenter distribution direction of major earthquake and aftershocks, seismic and geological data of earthquake areas, and damage degree of local buildings, 4 survey lines with a length of 30km were arranged across the epicenters and adjacent areas, and the concentrations of Rn, CO2 and Hg in soil gas were measured on site, and the results are as follows:

(1)There are obvious spatial differences in the concentrations of soil gas near the epicenter and its vicinities within the distance of 30km. Gas concentrations are relatively high near the epicenter areas and the east and west ends of 4 arranged survey lines, in contrast to those which are relatively low in other non-structural control regions. The spatial distribution pattern of Rn concentration in soil gas is basically consistent with that of CO2, which may be due to CO2 used as a carrier gas of Rn to migrate to the surface. At the southern end of the Lingxian-Guanxian Fault(F1), the spatial concentration patterns of Rn and CO2 gases exhibit multiple peaks or wide anomalous zones. It is speculated that the deformation zone of the fault rupture at this location is relatively wide, and there may be secondary permeable fracture zones in the west of the F1. The escape form of Rn and CO2 gas indicates that there may indeed be multiple small fault branches near the F1, and the fault structure is relatively complex.

(2)The spatial concentration distributions of Hg, Rn and CO2 in the epicenter areas are similar to that in its eastern region. However, in the western region of the epicenter areas, the spatial concentration distributions of Hg, Rn and CO2 vary greatly, and the Rn and CO2 concentrations near the Jiucheng Fault(F3) in the west of the epicenter regions are higher than those near epicenters. It is speculated that this phenomenon may be related to the high-concentration gas migration caused by strong seismic tectonic activities and the special nasal geological structure controlled by F3.

(3)The concentrations of Rn, CO2 and Hg in the soil show high-value anomaly zones near the F1 and F3, and the concentrations of Rn and CO2 in the west of F3 exceed those in the epicenter area. After further earthquake relocation analysis, the spatial distribution of aftershocks exhibit a trend from F1 to F3. Combined with geochemical and geophysical research results, it is inferred that Pingyuan M5.5 earthquake should be related to the deep tectonic activities of F1 and F3.

Above research results show that the soil gas geochemical method can be applied to define the location and distribution direction of the buried faults with thick overburden, which provides an important criterion for earthquake trend tracking analysis. This study is of greatly scientific significance in determining the dynamic source and genetic mechanism of Pingyuan M5.5 earthquake, identifying potential strong earthquake hazard areas, and assessing the risk of future earthquakes in the study area.

Key words: Pingyuan M5.5 earthquake, Fault soil gas concentration, Lingxian-Guanxian Fault, Jiucheng Fault, Tectono-geochemistry