陕西凤翔井水位和区域应力场变化与地震活动性关系研究

doi:10.12196/j.issn.1000-3274.2024.03.009

摘要/Abstract

摘要： 陇县—宝鸡断裂带的北段闭锁程度较强, 但关于其南段的闭锁性研究较少。承压含水层的观测井被认为是灵敏的“体应变计”, 井水位的上升或下降变化往往能反映区域应力处于拉张或挤压状态。陕西凤翔井位于陇县—宝鸡断裂的中南段。基于对凤翔井水位在2013—2023年期间变化趋势的分析, 利用气压系数和M₂波潮汐因子等滑动拟合, 计算了不排水条件下, 该井含水层的孔隙度、固体骨架的体积压缩系数和水的体积压缩系数。通过该井水位变化量和含水层垂向应力变化量的关系式, 定量分析了该井周边地区构造应力场的时序特征。结合区域内GNSS基线和面应变变化, 以及2013年以来的地震活动, 综合分析认为, 该区域的应力场变化分为两个阶段: ① 2013—2017年, 凤翔井水位下降, 垂向应力减弱, 处于拉张环境, 地震频次较低; ② 2017—2023年, 凤翔井水位趋于平稳, 垂向应力在零值上下波动, 拉张减弱并逐渐转变为应力积累增强阶段, 地震频次有所增加。综合近十年凤翔井水位、垂向应力、 GNSS基线和面应变以及地震活动性分析可知, 陇县—宝鸡断裂带中南段应力积累较弱, 形变量较小, 处于相对稳定的状态。

关键词: 凤翔井, 水位, 应力场, 时序特征, 地震活动性

Abstract: The northern section of the Longxian-Baoji fault zone has a strong degree of locking, but the locking degree of its southern section is less studied. The observation well of a confined aquifer is considered a sensitive “volumetric strain gauge”, and the rise or fall of the well water level often reflects the state of regional stress in tension or compression. Fengxiang Well in Shaanxi is located in the central and southern section of the Longxian-Baoji Fault. Based on the analysis of the variation trend of the water level in Fengxiang Well from 2013 to 2023, the porosity of the aquifer, the volume compression coefficient of the solid skeleton, and the volume compression coefficient of the water were calculated for the aquifer of the well, under un-drained conditions, by using sliding fits such as the barometric pressure coefficient and the M₂-wave tidal factor. The temporal characteristics of the tectonic stress field around the well were quantitatively analyzed by using the relationship between the water level variation of the well and the vertical stress variation of the aquifer. Based on the GNSS baseline and surface strain variation characteristics within the region, as well as the seismic activity characteristics since 2013, a comprehensive analysis suggests that the stress field variation characteristics in the region can be divided into two stages: ① From 2013 to 2017, the water level of Fengxiang well decreased, and the vertical stress weakened, showing a tensile environment with low seismic frequency. ② From 2017 to 2023, the water level of Fengxiang well tended to stabilize, and the vertical stress fluctuated around zero. The tension weakened and gradually transformed into a stage of stress accumulation and enhancement, with a significant increase in the number of earthquakes. Based on the analysis of the water level, vertical stress, GNSS baseline and surface strain, as well as seismic activity characteristics in the Fengxiang well over the past decade, it can be concluded that the central and southern sections of the Longxian Baoji fault zone is in a relatively stable state with weak stress accumlation and small deformation.

Key words: Fengxiang well, Water level, Stress field, Temporal characteristics, Seismic activity

中图分类号:

P315.7

刘洁, 翟宏光, 张国强, 朱琳, 邱玉荣. 陕西凤翔井水位和区域应力场变化与地震活动性关系研究[J]. 地震, 2024, 44(3): 124-137.

LIU Jie, ZHAI Hong-guang, ZHANG Guo-qiang, ZHU Lin, QIU Yu-rong. Study on the Relationship between Water Level in Fengxiang Well, Regional Stress Field Change and Seismic Activity in Shaanxi[J]. EARTHQUAKE, 2024, 44(3): 124-137.

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