水地球化学和稳定同位素变化记录了印度东北部地区地震后的地下水混合情况

IF 2.9 2区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Sourav Kumar, Michael Manga, Archana M. Nair, Abhishek Dixit, Chandan Mahanta
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引用次数: 0

摘要

地震引起的水文地质系统变化可追溯到 2000 多年前。作为我们正在进行的研究此类变化的水文地质化学监测工作的一部分,我们在 2021 年 2 月至 2023 年 7 月期间,每周两次从印度东北部科皮里断裂带的两口钻井中采集了 406 个地下水样本。我们分析了稳定同位素比值(δ2H、δ18O)和溶解元素浓度,从而获得了 2.5 年的水文地球化学时间序列以及在监测期内对多次区域地震(Mw ≥ 3)的响应。我们发现,在 2021 年阿萨姆 Mw 6.4 级地震之后,其中一口观测井(OW1)的地下水化学成分和同位素成分出现了明显但短暂的异常,随后两口井的水文化学成分都发生了长时间的变化。我们没有发现任何前兆变化。利用多元统计技术并分析主震前后的成分变化,我们推断 OW1 井的水化学异常代表了对主震的直接反应,可归因于水文屏障的潜在破坏。这反过来又使得新的水渗入 OW1 含水层,这些水可能来自附近的雅鲁藏布江。随后,在异常后时期,地震引起的断裂和相关的渗透性变化使地表水和地下水之间的混合持续了很长时间,从而在两口井中形成了新的水化学。我们的研究结果突显了地震期间含水层属性的动态性质。对这种变化进行长期连续的评估,可为了解地壳构造和流体流动之间的反馈提供新的视角。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Water Geochemistry and Stable Isotope Changes Record Groundwater Mixing After a Regional Earthquake in Northeast India

Water Geochemistry and Stable Isotope Changes Record Groundwater Mixing After a Regional Earthquake in Northeast India

Recorded earthquake-induced changes in hydrogeological systems date back over 2,000 years. As a part of our ongoing hydrogeochemical monitoring effort to study such changes, we collected 406 groundwater samples twice a week between February 2021 and July 2023 from two bore wells in the Kopili fault zone of Northeast India. We analyzed stable isotope ratios (δ2H, δ18O) and dissolved element concentrations to obtain a 2.5-year hydrogeochemical time series and responses to multiple regional earthquakes (Mw ≥ 3) within the monitored period. We find significant but transient anomalies in both the chemical and isotopic composition of groundwater at one of the observation wells (OW1) after the 2021 Assam Mw 6.4 earthquake, followed by prolonged alterations in the hydrochemistry at both wells. We do not identify any precursory changes. Using multivariate statistical techniques and analyzing compositional changes before and after the mainshock, we infer that the hydrochemical anomalies at OW1, representing an immediate response to the mainshock, can be attributed to the potential breach of a hydrological barrier. This, in turn, allowed the infiltration of new water into the OW1 aquifer, potentially sourced from the nearby Brahmaputra River. Subsequently, during the post-anomaly period, the earthquake-induced fracturing and the associated changes in permeability sustained a prolonged period of mixing between surface water and groundwater, resulting in newly formed hydrochemistry at both wells. Our findings highlight the dynamic nature of aquifer properties during earthquakes. Long-term continuous evaluation of such changes may provide new insights into feedback between tectonics and fluid flow in the crust.

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来源期刊
Geochemistry Geophysics Geosystems
Geochemistry Geophysics Geosystems 地学-地球化学与地球物理
CiteScore
5.90
自引率
11.40%
发文量
252
审稿时长
1 months
期刊介绍: Geochemistry, Geophysics, Geosystems (G3) publishes research papers on Earth and planetary processes with a focus on understanding the Earth as a system. Observational, experimental, and theoretical investigations of the solid Earth, hydrosphere, atmosphere, biosphere, and solar system at all spatial and temporal scales are welcome. Articles should be of broad interest, and interdisciplinary approaches are encouraged. Areas of interest for this peer-reviewed journal include, but are not limited to: The physics and chemistry of the Earth, including its structure, composition, physical properties, dynamics, and evolution Principles and applications of geochemical proxies to studies of Earth history The physical properties, composition, and temporal evolution of the Earth''s major reservoirs and the coupling between them The dynamics of geochemical and biogeochemical cycles at all spatial and temporal scales Physical and cosmochemical constraints on the composition, origin, and evolution of the Earth and other terrestrial planets The chemistry and physics of solar system materials that are relevant to the formation, evolution, and current state of the Earth and the planets Advances in modeling, observation, and experimentation that are of widespread interest in the geosciences.
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