地震地质 ›› 2022, Vol. 44 ›› Issue (5): 1225-1239.DOI: 10.3969/j.issn.0253-4967.2022.05.009

• 研究论文 • 上一篇    下一篇

2017年8月9日精河MS6.6地震宏观烈度及其余震分布的断层气体地球化学表征

朱成英1),2)(), 闫玮1),*(), 麻荣1), 李志海4), 汪成国1), 黄建明1), 周晓成3)   

  1. 1)新疆维吾尔自治区地震局, 乌鲁木齐 830011
    2)深圳防灾减灾技术研究院, 深圳 518003
    3)中国地震局地震预测研究所, 北京 100036
    4)宁波市应急管理局, 宁波 315066
  • 收稿日期:2021-07-16 修回日期:2021-09-03 出版日期:2022-10-20 发布日期:2022-11-28
  • 通讯作者: 闫玮
  • 作者简介:

    朱成英, 女, 1976年生, 2001年于烟台师范学院(现鲁东大学)获化学专业学士学位, 高级工程师, 主要从事地震地下流体的研究工作, 电话: 0991-3847542, E-mail:

  • 基金资助:
    中国地震局地震科技星火计划项目(XH20066); 新疆地震科学基金(202117)

GEOCHEMICAL CHARACTERIZATION OF FAULT GAS IN MACRO-SEISMIC INTENSITY AND AFTERSHOCK DISTRIBUTION OF JINGHE MS6.6 EARTHQUAKE ON AUGUST 9, 2017

ZHU Cheng-ying1),2)(), YAN Wei1)(), MA Rong1), LI Zhi-hai4), WANG Cheng-guo1), HUANG Jian-ming1), ZHOU Xiao-cheng3)   

  1. 1) Earthquake Agency of Xinjiang Uygur Autonomous Region, Urumqi 830011, China
    2) Shenzhen Academy of Disaster Prevention and Reduction, Shenzhen 518003, China
    3) Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China
    4) Bureau of Emergency Management of Ningbo, Ningbo 315066, China
  • Received:2021-07-16 Revised:2021-09-03 Online:2022-10-20 Published:2022-11-28
  • Contact: YAN Wei

摘要:

2017年8月9日7时27分52秒, 新疆博尔塔拉州精河县发生 MS6.6 地震, 震中位于库松木契克山前断裂的东段。为研究精河 MS6.6 地震后其周边断裂的活动特征, 对库松木契克山前断裂及博罗科努-阿其克库都克断裂精河段开展跨断层土壤逸出气体Rn、 H2、 CO2的浓度测量。结果表明: 1)土壤气体Rn、 CO2和H2的浓度有较好的一致性, 高值出现在断层附近, 多呈现明显的单峰特征。2)Rn、 CO2和H2浓度在空间上有明显的分段特征, 从西向东浓度值逐渐增大, 主震和余震集中区附近达到最高值, 博罗科努-阿其克库都克断裂精河段的土壤气浓度达到最低值。3)Rn、 CO2的浓度异常强度有很好的一致性, 两者的高、 低值分布区域与H2基本相反。余震集中的区域也是断层活动增强的区域, 随着余震的发生, 应力增加, 岩石的渗透性减小, 使得不能参与扩散和对流等迁移活动的Rn被CO2从地下深部携带至地表, 这能解释Rn和CO2出现同步异常的原因; H2主要被封存于深部的岩石孔隙和裂隙中, 地震发生后, 岩石中的孔隙受到破坏, H2迅速逃逸到浅部或大气中。一方面, 随着余震的发生来自浅部气藏的H2量越来越少; 另一方面, 岩石中因化学反应产生的H2生成量随断层活动性的降低而下降。4)土壤气Rn、 CO2和H2的浓度大小与余震分布和地震宏观烈度有较好的一致性, 及时在震区和外围区域开展土壤气体地球化学观测是震后趋势判定的一种有效手段和方法, 也可把跨断层土壤气体的浓度作为地震宏观烈度评定的重要补充资料。

关键词: 精河6.6级地震, 跨断层土壤气体, 地球化学, 气体浓度

Abstract:

An MS6.6 earthquake struck Jinghe County, Boltala Prefecture, Xinjiang at 7:27:52 am on August 9, 2017, with the epicenter located in the eastern section of the Cusongmuqike piedmont fault. In order to study the activity characteristics of the faults around Jinghe after the MS6.6 earthquake, the field survey and selection of the Cusongmuqike piedmont fault and the Jinghe section of the Bolokenu-Aqikekuduke Fault were carried out from October 18 to November 3, 2017. Mobile monitoring of soil gas geochemistry was carried out at 191 survey points respectively on 12 survey lines of Cusongmuqike piedmont fault and two survey lines on the Jinghe section of Bolokenu-Aqikekuduke Fault, and the concentrations of Rn, H2 and CO2 emitted from soil across the fault were observed. The results show that: 1)The concentrations of soil gases Rn, CO2 and H2 were consistent, and the high values appeared near the faults, with obvious single-peak characteristics. 2)The concentration of Rn, CO2 and H2 increased gradually from west to east and reached the highest value near the main shock and aftershock areas, and the concentration of soil gas reached the lowest value in the Jinghe section of the Bolokenu-Aqikekuduke Fault. 3)There is a good consistency between Rn and CO2 concentration anomaly intensity, and the distribution regions of both are basically opposite to H2 concentration anomaly intensity. The high values of soil gas Rn and CO2 anomaly intensity mainly concentrated in the west of the epicenter area of Jinghe MS6.6 earthquake(line 7, 8, 9 and 10 area), which was the aftershock concentration area, and the lowest value of H2 anomaly intensity appeared in this area. Reason may be that the aftershock concentration area was also the fault activity enhancement area, with the occurrence of aftershocks, stress increased, the permeability of rock decreased, and the gas in fault pores released sustainedly, causing the concentration change of gases emitted from fault. Since Rn cannot participate in the migration activities such as diffusion and convection, it was brought to the surface from deep underground carried by CO2, this could explain the abnormal synchronization of Rn and CO2. Hydrogen, as the element with the smallest particle size, lightest mass, fastest migration speed and strongest penetration, mainly comes from the trapped hydrogen in the pores and fissures of deep rock. After the earthquake, the pores in the rock were damaged, and hydrogen rapidly emitted to the shallow part or atmosphere. On the one hand, with the occurrence of aftershocks, the amount of H2 from shallow gas reservoirs was decreasing. On the other hand, the generation of H2 produced by chemical reactions in rocks decreased with the decrease of fault activity. The measurement was done more than 70 days after the occurrence of the main shock, during which the activity of strong aftershocks tended to end and the activity of the fault also weakened. 4)Concentrations of soil gas Rn, CO2 and H2 have a good consistency with the distribution of aftershocks and the macroseismic intensity, so, carrying out in a timely manner the soil gas geochemical observation is an effective means and method for earthquake trend judgment, soil gas geochemical observation in and around the earthquake area is a kind of effective means and methods for earthquake trend judgement, and the cross-fault soil gas concentrations can also be used as an important supplement to the macroseismic intensity evaluation.

Key words: Jinghe MS6.6 earthquake, cross-fault soil gas, geochemistry, gas concentration