Sourav Kumar, Michael Manga, Archana M. Nair, Abhishek Dixit, Chandan Mahanta
{"title":"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","authors":"Sourav Kumar, Michael Manga, Archana M. Nair, Abhishek Dixit, Chandan Mahanta","doi":"10.1029/2024GC011476","DOIUrl":null,"url":null,"abstract":"<p>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 (δ<sup>2</sup>H, δ<sup>18</sup>O) 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.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"25 7","pages":""},"PeriodicalIF":2.9000,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011476","citationCount":"0","resultStr":"{\"title\":\"Water Geochemistry and Stable Isotope Changes Record Groundwater Mixing After a Regional Earthquake in Northeast India\",\"authors\":\"Sourav Kumar, Michael Manga, Archana M. Nair, Abhishek Dixit, Chandan Mahanta\",\"doi\":\"10.1029/2024GC011476\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>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 (δ<sup>2</sup>H, δ<sup>18</sup>O) 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.</p>\",\"PeriodicalId\":50422,\"journal\":{\"name\":\"Geochemistry Geophysics Geosystems\",\"volume\":\"25 7\",\"pages\":\"\"},\"PeriodicalIF\":2.9000,\"publicationDate\":\"2024-07-14\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011476\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Geochemistry Geophysics Geosystems\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1029/2024GC011476\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geochemistry Geophysics Geosystems","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2024GC011476","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
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.
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.