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Simon Loew - One of the best experts on this subject based on the ideXlab platform.
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Long-term transient Groundwater Pressure and deep infiltration in Alpine mountain slopes (Poschiavo Valley, Switzerland)
Hydrogeology Journal, 2019Co-Authors: Larissa Palézieux, Simon LoewAbstract:Les aquifères de socle des bassins versants alpins constituent des ressources régionales d’eau douce importantes. Les données concernant les processus de recharge des eaux souterraines du socle sont rares et les dynamiques à l’œuvre mal comprises. Les principaux jeux de données utilisés pour contraindre la recharge et l’écoulement des eaux souterraines à l’échelle régionale reposaient jusqu’à présent sur des méthodes indirectes (isotopes environnementaux, taux de décharge en rivière, débits des sorties en galerie). Ici, une base de données unique est présentée sur les variations de pressions interstitielles mesurées depuis 10 ans sur cinq forages profonds situés dans les parties supérieures d’un versant montagneux, à 1,500–2,300 m au-dessus du niveau de la mer. En plus des enregistrements des pressions interstitielles à plusieurs profondeurs, une analyse détaillée des conditions hydrogéologiques dans un bassin versant des Alpes est fournie parallèlement aux résultats des investigations sur les mécanismes de recharge des eaux souterraines en réponse aux variations des conditions climatiques et des propriétés hydrauliques du massif rocheux. Les données de pression enregistrées montrent des variations annuelles, avec des amplitudes de 5–45 m et des réponses en quelques jours aux pluies torrentielles d’été dans une gamme de profondeurs accessible de 45–277 m sous la surface du sol. Des modèles analytiques unidimensionnels de diffusion des pressions interstitielles et des modèles numériques d’infiltration ont été appliqués pour étudier la dynamique des pressions interstitielles et les variations de la nappe phréatique. Les résultats du modèle reproduisent les paramètres suivants pour la couche supérieure de 100 m d’épaisseur: les amplitudes observées, les taux et les retards de l’accroissement de la pression avec des porosités de 0.05-0.10%, des emmagasinements spécifiques de 5E-5 à 5E-7 m^-1 et des diffusivités hydrauliques de 1E-1 à 1E-3 m^2/s. Les forages localisés dans les zones de forte diffusivité (socle fortement fracturé sous des dépôts de pente grossiers) ont présenté les variations de pression les plus fortes et ont été les plus sensibles aux conditions météorologiques. Bedrock aquifers in alpine catchments are important regional sources of freshwater. Data regarding bedrock Groundwater-recharge processes are scarce and governing dynamics are poorly understood. The main datasets used to constrain regional Groundwater recharge and flow, so far, have been based on indirect methods (environmental isotopes, river discharge rates, tunnel inflows). Here, a unique dataset is presented of long-term pore-water-Pressure measurements from five deep boreholes situated in the upper reaches of a mountain slope at 1,500–2,300 m above sea level. In addition to multilevel pore Pressure records, a detailed analysis of the hydrogeological conditions in the Alpine catchment is provided, along with the results from investigations of Groundwater recharge mechanisms in response to variations in climatic conditions and hydraulic rock-mass properties. The recorded Pressure data show annual Pressure variations with amplitudes of 5–45 m and responses within a few days to summer rainstorms in the available depth range of 45–277 m below ground surface. One-dimensional analytical pore-Pressure diffusion models and numerical infiltration models were applied to investigate pore-Pressure dynamics and water-table variations. The model results reproduced the following parameters for the uppermost 100-m-thick layer: the observed amplitudes, rates and delays of Pressure increase with porosities of 0.05–0.1%, specific storage of 5E-5 to 5E-7 m^-1, and hydraulic diffusivities of 1E-1 to 1E-3 m^2/s. Boreholes located in high-diffusivity areas (strongly fractured bedrock below coarse slope debris) had the strongest Pressure variations and were most sensitive to weather conditions. Los acuíferos del basamento en las cuencas alpinas son importantes fuentes regionales de agua dulce. Los datos relativos a los procesos de recarga de aguas subterráneas son escasos y la dinámica que los gobiernan no se conocen bien. Los principales conjuntos de datos utilizados para identificar la recarga y el flujo regional de las aguas subterráneas, hasta ahora, se han basado en métodos indirectos (isótopos ambientales, tasas de descarga de los ríos, ingresos en túneles). Aquí se presenta un conjunto de datos únicos de mediciones de presión de poros a largo plazo de cinco pozos profundos situados en los tramos superiores de una ladera de montaña a 1,500–2,300 m sobre el nivel del mar. Además de los registros de presión de poros en varios niveles, se proporciona un análisis detallado de las condiciones hidrogeológicas en la cuenca alpina, junto con los resultados de las investigaciones de los mecanismos de recarga de las aguas subterráneas en respuesta a las variaciones de las condiciones climáticas y las propiedades hidráulicas de la masa rocosa. Los datos de presión registrados muestran variaciones anuales con amplitudes de 5-45 m y respuestas en pocos días a tormentas de verano en el rango de profundidad disponible de 45-277 m bajo la superficie del suelo. Se aplicaron modelos analíticos unidimensionales de difusión de presión de poros y modelos numéricos de infiltración para investigar la dinámica de la presión de poros y las variaciones de la capa freática. Los resultados del modelo reprodujeron los siguientes parámetros para la capa superior de 100 m de espesor: las amplitudes, tasas y retardos observados de aumento de presión con porosidades de 0.05-0.1%, almacenamiento específico de 5E-5 a 5E-7 m^-1, y difusividades hidráulicas de 1E-1 a 1E-3 3 m^2/s. Los pozos de sondeo ubicados en áreas de alta difusividad (basamento fuertemente fracturado debajo de pendientes de escombros gruesos) tuvieron las variaciones de presión más fuertes y fueron los más sensibles a las condiciones climáticas. Os aquíferos de embasamento cristalino em bacias alpinas são importantes fontes regionais de água doce. Os dados referentes aos processos de recarga das águas subterrâneas são raros e as dinâmicas de controle são pouco compreendidas. Os principais conjuntos de dados usados para restringir a recarga e fluxo regional das águas subterrâneas, até agora, têm sido baseados em métodos indiretos (isótopos ambientais, taxas de descarga de rios, entradas de túneis). Aqui, é apresentado um conjunto de dados único de medições a longo prazo da pressão dos poros de cinco furos profundos situados nos limites superiores de uma encosta de montanha entre 1,500 e 2,300 m acima do nível do mar. Além dos registros multiníveis de pressão de poros, é fornecida uma análise detalhada das condições hidrogeológicas na bacia dos Alpes, juntamente com os resultados das investigações dos mecanismos de recarga das águas subterrâneas em resposta a variações nas condições climáticas e nas propriedades hidráulicas da massa rochosa. Os dados de pressão registrados mostram variações de pressão anuais com amplitudes de 5–45 m e respostas dentro de alguns dias para tempestades de verão na faixa de profundidade disponível de 45–277 m abaixo da superfície. Modelos analíticos unidimensionais de difusão de poro-pressão e modelos de infiltração numérica foram aplicados para investigar a dinâmica da pressão dos poros e as variações do lençol freático. Os resultados do modelo reproduziram os seguintes parâmetros para a camada mais alta de 100 m de espessura: as amplitudes, taxas e atrasos de pressão observados aumentam com porosidades de 0.05 a 0.1%, armazenamento específico de 5E-5 a 5E-7 m^-1 e difusividades hidráulicas de 1E-1 a 1E-3 m^2/s. Os furos localizados em áreas de elevada difusividade (fragmentos rochosos fortemente fraturados abaixo dos resíduos de declive grosseiro) apresentavam as variações de pressão mais fortes e eram mais sensíveis às condições meteorológicas. 高山流域基岩含水层是重要的区域淡水水源。关于基岩地下水补给过程的数据很少,而且对其动态变化的控制机理了解很少。到目前为止,用于约束区域地下水补给和流动的主要数据是基于间接方法(环境同位素,河流流量,隧道渗入等的量测)。本文提供了一个独特的数据集,包括位于海拔1,500–2,300米的山坡上游的五个深井内的孔隙水压力的长期监测数据。除了不同海拔位置的孔隙压力记录,本文还提供了阿尔卑斯流域水文地质条件的详细分析,并对气候变化和岩体水力特性变化影响下的地下水补给机制进行了调查分析。记录的压力数据显示年际压力变化幅度为5到45米,并记录了由于夏季暴雨引起持续几天的压力变化(监测深度范围为地表以下45-277米)。应用一维分析孔隙 - 压力扩散模型和入渗数值模型研究了孔隙压力动态演变和水位变化。模型结果重现了地表下100米范围内的特征:所观测到的水压力变化幅值、水压力增加的速率和延迟效应等随孔隙率(0.05–0.1%)、单位储水系数(5E-5至5E-7 m^-1)以及压力扩散系数(1E-1至1E-3 m^2/s)等的变化。位于高扩散系数区域(在斜坡粗碎片下方的强烈破碎基岩区域)的钻孔显示出最强的压力变化,并且对天气条件最敏感。
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Long-term transient Groundwater Pressure and deep infiltration in Alpine mountain slopes (Poschiavo Valley, Switzerland)
Hydrogeology Journal, 2019Co-Authors: Larissa Palézieux, Simon LoewAbstract:Bedrock aquifers in alpine catchments are important regional sources of freshwater. Data regarding bedrock Groundwater-recharge processes are scarce and governing dynamics are poorly understood. The main datasets used to constrain regional Groundwater recharge and flow, so far, have been based on indirect methods (environmental isotopes, river discharge rates, tunnel inflows). Here, a unique dataset is presented of long-term pore-water-Pressure measurements from five deep boreholes situated in the upper reaches of a mountain slope at 1,500–2,300 m above sea level. In addition to multilevel pore Pressure records, a detailed analysis of the hydrogeological conditions in the Alpine catchment is provided, along with the results from investigations of Groundwater recharge mechanisms in response to variations in climatic conditions and hydraulic rock-mass properties. The recorded Pressure data show annual Pressure variations with amplitudes of 5–45 m and responses within a few days to summer rainstorms in the available depth range of 45–277 m below ground surface. One-dimensional analytical pore-Pressure diffusion models and numerical infiltration models were applied to investigate pore-Pressure dynamics and water-table variations. The model results reproduced the following parameters for the uppermost 100-m-thick layer: the observed amplitudes, rates and delays of Pressure increase with porosities of 0.05–0.1%, specific storage of 5E-5 to 5E-7 m-1, and hydraulic diffusivities of 1E-1 to 1E-3 m2/s. Boreholes located in high-diffusivity areas (strongly fractured bedrock below coarse slope debris) had the strongest Pressure variations and were most sensitive to weather conditions.
Michael Manga - One of the best experts on this subject based on the ideXlab platform.
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When it rains, lava pours
Nature, 2020Co-Authors: Michael MangaAbstract:Heavy rainfall might have altered the eruption of Kīlauea volcano. Early 2018 saw unusually heavy rainfall in Hawaii. Modelling now suggests that Groundwater Pressure increased owing to rainfall: this might have triggered changes in the eruption of the island’s Kīlauea volcano.
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A mechanism for sustained Groundwater Pressure changes induced by distant earthquakes
Journal of Geophysical Research, 2003Co-Authors: Emily E. Brodsky, Evelyn Roeloffs, Douglas Woodcock, Ivan Gall, Michael MangaAbstract:[1] Large, sustained well water level changes (>10 cm) in response to distant (more than hundreds of kilometers) earthquakes have proven enigmatic for over 30 years. Here we use high sampling rates at a well near Grants Pass, Oregon, to perform the first simultaneous analysis of both the dynamic response of water level and sustained changes, or steps. We observe a factor of 40 increase in the ratio of water level amplitude to seismic wave ground velocity during a sudden coseismic step. On the basis of this observation we propose a new model for coseismic pore Pressure steps in which a temporary barrier deposited by Groundwater flow is entrained and removed by the more rapid flow induced by the seismic waves. In hydrothermal areas, this mechanism could lead to 4 � 10 � 2 MPa Pressure changes and triggered seismicity. INDEX TERMS: 1829 Hydrology: Groundwater hydrology; 7209 Seismology: Earthquake dynamics and mechanics; 7212 Seismology: Earthquake ground motions and engineering; 7260 Seismology: Theory and modeling; 7294 Seismology: Instruments and techniques; KEYWORDS: earthquakes, triggering, time-dependent hydrology, fractures Citation: Brodsky, E. E., E. Roeloffs, D. Woodcock, I. Gall, and M. Manga, A mechanism for sustained Groundwater Pressure changes induced by distant earthquakes, J. Geophys. Res., 108(B8), 2390, doi:10.1029/2002JB002321, 2003.
Larissa Palézieux - One of the best experts on this subject based on the ideXlab platform.
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Long-term transient Groundwater Pressure and deep infiltration in Alpine mountain slopes (Poschiavo Valley, Switzerland)
Hydrogeology Journal, 2019Co-Authors: Larissa Palézieux, Simon LoewAbstract:Les aquifères de socle des bassins versants alpins constituent des ressources régionales d’eau douce importantes. Les données concernant les processus de recharge des eaux souterraines du socle sont rares et les dynamiques à l’œuvre mal comprises. Les principaux jeux de données utilisés pour contraindre la recharge et l’écoulement des eaux souterraines à l’échelle régionale reposaient jusqu’à présent sur des méthodes indirectes (isotopes environnementaux, taux de décharge en rivière, débits des sorties en galerie). Ici, une base de données unique est présentée sur les variations de pressions interstitielles mesurées depuis 10 ans sur cinq forages profonds situés dans les parties supérieures d’un versant montagneux, à 1,500–2,300 m au-dessus du niveau de la mer. En plus des enregistrements des pressions interstitielles à plusieurs profondeurs, une analyse détaillée des conditions hydrogéologiques dans un bassin versant des Alpes est fournie parallèlement aux résultats des investigations sur les mécanismes de recharge des eaux souterraines en réponse aux variations des conditions climatiques et des propriétés hydrauliques du massif rocheux. Les données de pression enregistrées montrent des variations annuelles, avec des amplitudes de 5–45 m et des réponses en quelques jours aux pluies torrentielles d’été dans une gamme de profondeurs accessible de 45–277 m sous la surface du sol. Des modèles analytiques unidimensionnels de diffusion des pressions interstitielles et des modèles numériques d’infiltration ont été appliqués pour étudier la dynamique des pressions interstitielles et les variations de la nappe phréatique. Les résultats du modèle reproduisent les paramètres suivants pour la couche supérieure de 100 m d’épaisseur: les amplitudes observées, les taux et les retards de l’accroissement de la pression avec des porosités de 0.05-0.10%, des emmagasinements spécifiques de 5E-5 à 5E-7 m^-1 et des diffusivités hydrauliques de 1E-1 à 1E-3 m^2/s. Les forages localisés dans les zones de forte diffusivité (socle fortement fracturé sous des dépôts de pente grossiers) ont présenté les variations de pression les plus fortes et ont été les plus sensibles aux conditions météorologiques. Bedrock aquifers in alpine catchments are important regional sources of freshwater. Data regarding bedrock Groundwater-recharge processes are scarce and governing dynamics are poorly understood. The main datasets used to constrain regional Groundwater recharge and flow, so far, have been based on indirect methods (environmental isotopes, river discharge rates, tunnel inflows). Here, a unique dataset is presented of long-term pore-water-Pressure measurements from five deep boreholes situated in the upper reaches of a mountain slope at 1,500–2,300 m above sea level. In addition to multilevel pore Pressure records, a detailed analysis of the hydrogeological conditions in the Alpine catchment is provided, along with the results from investigations of Groundwater recharge mechanisms in response to variations in climatic conditions and hydraulic rock-mass properties. The recorded Pressure data show annual Pressure variations with amplitudes of 5–45 m and responses within a few days to summer rainstorms in the available depth range of 45–277 m below ground surface. One-dimensional analytical pore-Pressure diffusion models and numerical infiltration models were applied to investigate pore-Pressure dynamics and water-table variations. The model results reproduced the following parameters for the uppermost 100-m-thick layer: the observed amplitudes, rates and delays of Pressure increase with porosities of 0.05–0.1%, specific storage of 5E-5 to 5E-7 m^-1, and hydraulic diffusivities of 1E-1 to 1E-3 m^2/s. Boreholes located in high-diffusivity areas (strongly fractured bedrock below coarse slope debris) had the strongest Pressure variations and were most sensitive to weather conditions. Los acuíferos del basamento en las cuencas alpinas son importantes fuentes regionales de agua dulce. Los datos relativos a los procesos de recarga de aguas subterráneas son escasos y la dinámica que los gobiernan no se conocen bien. Los principales conjuntos de datos utilizados para identificar la recarga y el flujo regional de las aguas subterráneas, hasta ahora, se han basado en métodos indirectos (isótopos ambientales, tasas de descarga de los ríos, ingresos en túneles). Aquí se presenta un conjunto de datos únicos de mediciones de presión de poros a largo plazo de cinco pozos profundos situados en los tramos superiores de una ladera de montaña a 1,500–2,300 m sobre el nivel del mar. Además de los registros de presión de poros en varios niveles, se proporciona un análisis detallado de las condiciones hidrogeológicas en la cuenca alpina, junto con los resultados de las investigaciones de los mecanismos de recarga de las aguas subterráneas en respuesta a las variaciones de las condiciones climáticas y las propiedades hidráulicas de la masa rocosa. Los datos de presión registrados muestran variaciones anuales con amplitudes de 5-45 m y respuestas en pocos días a tormentas de verano en el rango de profundidad disponible de 45-277 m bajo la superficie del suelo. Se aplicaron modelos analíticos unidimensionales de difusión de presión de poros y modelos numéricos de infiltración para investigar la dinámica de la presión de poros y las variaciones de la capa freática. Los resultados del modelo reprodujeron los siguientes parámetros para la capa superior de 100 m de espesor: las amplitudes, tasas y retardos observados de aumento de presión con porosidades de 0.05-0.1%, almacenamiento específico de 5E-5 a 5E-7 m^-1, y difusividades hidráulicas de 1E-1 a 1E-3 3 m^2/s. Los pozos de sondeo ubicados en áreas de alta difusividad (basamento fuertemente fracturado debajo de pendientes de escombros gruesos) tuvieron las variaciones de presión más fuertes y fueron los más sensibles a las condiciones climáticas. Os aquíferos de embasamento cristalino em bacias alpinas são importantes fontes regionais de água doce. Os dados referentes aos processos de recarga das águas subterrâneas são raros e as dinâmicas de controle são pouco compreendidas. Os principais conjuntos de dados usados para restringir a recarga e fluxo regional das águas subterrâneas, até agora, têm sido baseados em métodos indiretos (isótopos ambientais, taxas de descarga de rios, entradas de túneis). Aqui, é apresentado um conjunto de dados único de medições a longo prazo da pressão dos poros de cinco furos profundos situados nos limites superiores de uma encosta de montanha entre 1,500 e 2,300 m acima do nível do mar. Além dos registros multiníveis de pressão de poros, é fornecida uma análise detalhada das condições hidrogeológicas na bacia dos Alpes, juntamente com os resultados das investigações dos mecanismos de recarga das águas subterrâneas em resposta a variações nas condições climáticas e nas propriedades hidráulicas da massa rochosa. Os dados de pressão registrados mostram variações de pressão anuais com amplitudes de 5–45 m e respostas dentro de alguns dias para tempestades de verão na faixa de profundidade disponível de 45–277 m abaixo da superfície. Modelos analíticos unidimensionais de difusão de poro-pressão e modelos de infiltração numérica foram aplicados para investigar a dinâmica da pressão dos poros e as variações do lençol freático. Os resultados do modelo reproduziram os seguintes parâmetros para a camada mais alta de 100 m de espessura: as amplitudes, taxas e atrasos de pressão observados aumentam com porosidades de 0.05 a 0.1%, armazenamento específico de 5E-5 a 5E-7 m^-1 e difusividades hidráulicas de 1E-1 a 1E-3 m^2/s. Os furos localizados em áreas de elevada difusividade (fragmentos rochosos fortemente fraturados abaixo dos resíduos de declive grosseiro) apresentavam as variações de pressão mais fortes e eram mais sensíveis às condições meteorológicas. 高山流域基岩含水层是重要的区域淡水水源。关于基岩地下水补给过程的数据很少,而且对其动态变化的控制机理了解很少。到目前为止,用于约束区域地下水补给和流动的主要数据是基于间接方法(环境同位素,河流流量,隧道渗入等的量测)。本文提供了一个独特的数据集,包括位于海拔1,500–2,300米的山坡上游的五个深井内的孔隙水压力的长期监测数据。除了不同海拔位置的孔隙压力记录,本文还提供了阿尔卑斯流域水文地质条件的详细分析,并对气候变化和岩体水力特性变化影响下的地下水补给机制进行了调查分析。记录的压力数据显示年际压力变化幅度为5到45米,并记录了由于夏季暴雨引起持续几天的压力变化(监测深度范围为地表以下45-277米)。应用一维分析孔隙 - 压力扩散模型和入渗数值模型研究了孔隙压力动态演变和水位变化。模型结果重现了地表下100米范围内的特征:所观测到的水压力变化幅值、水压力增加的速率和延迟效应等随孔隙率(0.05–0.1%)、单位储水系数(5E-5至5E-7 m^-1)以及压力扩散系数(1E-1至1E-3 m^2/s)等的变化。位于高扩散系数区域(在斜坡粗碎片下方的强烈破碎基岩区域)的钻孔显示出最强的压力变化,并且对天气条件最敏感。
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Long-term transient Groundwater Pressure and deep infiltration in Alpine mountain slopes (Poschiavo Valley, Switzerland)
Hydrogeology Journal, 2019Co-Authors: Larissa Palézieux, Simon LoewAbstract:Bedrock aquifers in alpine catchments are important regional sources of freshwater. Data regarding bedrock Groundwater-recharge processes are scarce and governing dynamics are poorly understood. The main datasets used to constrain regional Groundwater recharge and flow, so far, have been based on indirect methods (environmental isotopes, river discharge rates, tunnel inflows). Here, a unique dataset is presented of long-term pore-water-Pressure measurements from five deep boreholes situated in the upper reaches of a mountain slope at 1,500–2,300 m above sea level. In addition to multilevel pore Pressure records, a detailed analysis of the hydrogeological conditions in the Alpine catchment is provided, along with the results from investigations of Groundwater recharge mechanisms in response to variations in climatic conditions and hydraulic rock-mass properties. The recorded Pressure data show annual Pressure variations with amplitudes of 5–45 m and responses within a few days to summer rainstorms in the available depth range of 45–277 m below ground surface. One-dimensional analytical pore-Pressure diffusion models and numerical infiltration models were applied to investigate pore-Pressure dynamics and water-table variations. The model results reproduced the following parameters for the uppermost 100-m-thick layer: the observed amplitudes, rates and delays of Pressure increase with porosities of 0.05–0.1%, specific storage of 5E-5 to 5E-7 m-1, and hydraulic diffusivities of 1E-1 to 1E-3 m2/s. Boreholes located in high-diffusivity areas (strongly fractured bedrock below coarse slope debris) had the strongest Pressure variations and were most sensitive to weather conditions.
Damien Sous - One of the best experts on this subject based on the ideXlab platform.
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Field evidence of swash Groundwater circulation in the microtidal rousty beach, France
Advances in Water Resources, 2016Co-Authors: Damien Sous, Lise Petitjean, Vincent Rey, François Sabatier, Frederic Bouchette, Samuel Meulé, Kévin MartinsAbstract:This manuscript reports on a novel field experiment carried out on a microtidal beach in Camargue, France. For the first time in the field, a comprehensive description of the Groundwater dynamics under sandy beach swash zone is presented. A cross-shore network of 15 buried Pressure sensors is combined with terrestrial LiDAR measurements to study the swash-Groundwater dynamics. The presented data focus on the decay of a moderate storm which allows to monitor the evolution of the Groundwater Pressure field in response to the retreat of the swash zone. Both horizontal and vertical head gradients are measured within the porous sand soil to estimate the Groundwater flow field using Darcy's law. Time-averaged analysis demonstrates the presence of a rather consistent Groundwater circulation pattern under the swash zone, shifting offshore with the swash zone. The main tendency is an offshore directed flow, with infiltration/exfiltration in the upper/lower parts of the swash zone. Time-resolved analysis highlights the typical Groundwater response to swash events which consists mainly of an overall infiltration flow during the bed inundation by the swash tongue, a seaward flow during the swash retreat and, for long backwash events, a localized exfiltration flow under the next incoming uprush.
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Groundwater Pressure dynamics in a laboratory swash zone
Journal of Coastal Research, 2011Co-Authors: Damien Sous, Adrien Lambert, Hervé Michallet, Vincent ReyAbstract:As part of the MODLIT program, which is a laboratory qualification campaign for sandy beach morphodynamics model, an instrumental study has been conducted in the LHF multidirectional wave basin (Grenoble-INP / SOGREAH, France) . A key-point of the understanding of sandy beaches dynamics is the knowledge of the interactions between surface and Groundwater hydrodynamics, in particular between swash and beach watertable, and their impact on accretion and erosion processes above the still water level. A dedicated cross-shore line of 9 relative Pressure sensors has been deployed from the inner surf zone to the berm, combining buried and free sensors. Every sensors were located below the mean water level. Spectral analysis shows the low-pass filtering of Pressure waves and allows to discriminate the low frequency modes. A detailed sequence of Pressure field snapshots is presented to reveal the Groundwater flows and highlight the role of swash overtopping in Pressure gradients.
Naoji Koizumi - One of the best experts on this subject based on the ideXlab platform.
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Groundwater Pressure changes and crustal deformation before and after the 2007 and 2014 eruptions of Mt. Ontake
Earth Planets and Space, 2016Co-Authors: Naoji Koizumi, Yuichi Kitagawa, Tsutomu Sato, Tadafumi OchiAbstract:Volcanic activity generally causes crustal deformation, which sometimes induces Groundwater changes, and both of these phenomena are sometimes detected before volcanic eruptions. Therefore, investigations of crustal deformation and Groundwater changes can be useful for predicting volcanic eruptions. The Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, has been observing Groundwater Pressure at Ohtaki observatory (GOT) since 1998. GOT is about 10 km southeast of the summit of Mt. Ontake. During this observation period, Mt. Ontake has erupted twice, in 2007 and in 2014. Before the 2007 eruption, the Groundwater Pressure at GOT clearly dropped, but it did not change before or after the 2014 eruption. These observations are consistent with the crustal deformation observed by Global Navigation Satellite System stations of the Geospatial Information Authority of Japan. The difference between the 2007 and 2014 eruptions can be explained if a relatively large magma intrusion occurred before the 2007 eruption but no or a small magma intrusion before the 2014 eruption.
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Detection of short-term slow slip events along the Nankai Trough via Groundwater observations
Geophysical Research Letters, 2013Co-Authors: Yuichi Kitagawa, Naoji KoizumiAbstract:[1] In order to develop new tools or techniques to detect short-term slow slip events (S-SSEs) along subduction zones, we attempted to detect S-SSEs by conducting Groundwater Pressure observations. At ANO station, which is a Groundwater observation station operated by the Geological Survey of Japan, the National Institute of Advanced Industrial Science and Technology, for earthquake prediction research, Groundwater Pressures changed due to six S-SSEs that occurred near ANO from June 2011 to April in 2013. The fault models of these S-SSEs, which were estimated mainly by observing the crustal strains and tilts, explained the changes in the Groundwater Pressures. If the strain sensitivity of the observed Groundwater Pressure or level is larger than 1 mm/nstrain and the noise level is smaller than 50 mm/day, it is possible to detect S-SSEs that occur in southwest Japan by conducting Groundwater Pressure or level observations.
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Earthquake-related Changes in Groundwater Levels at the Dogo Hot Spring, Japan
Pure and Applied Geophysics, 2007Co-Authors: Satoshi Itaba, Naoji KoizumiAbstract:The Dogo hot spring, situated in Matsuyama City, Ehime Prefecture, Japan, is one of the oldest and most famous hot springs in Japan. The Groundwater level or discharge at the spring decreased four times during the past eight or nine Nankai earthquakes. These are large interplate earthquakes that have occurred repeatedly in the western part of the Nankai Trough at intervals of 100–200 years since A.D. 684. To clarify the mechanism of these earthquake-related changes in the water level at the spring, we analyzed Groundwater-level data recorded at the spring immediately after the 1946 Nankai earthquake and over the period from 1985 to 2006. We detected the other nine postseismic increases in Groundwater level and no decreases, except for a large decrease of 11.4 m related to the 1946 Nankai earthquake. The increases were probably caused by ground-shaking, while the decrease was caused by a change in coseismic volumetric strain. These results lead to the following explanation of the recorded earthquake-related changes in the Groundwater level at the Dogo hot spring. Both coseismic changes in volumetric strain and ground-shaking can lead to postseismic changes in Groundwater Pressure. The increase in Groundwater Pressure arising from ground-shaking is generally greater than the change in Pressure associated with changes in coseismic volumetric strain; however, at the time of the Nankai earthquakes, the spring experiences a large increase in coseismic volumetric strain, leading to a considerably larger decrease in the Groundwater level than the increase associated with ground-shaking. Therefore, the Groundwater level at the Dogo hot spring usually increases at times of relatively large earthquakes, although the Groundwater level or discharge decreases in the case of the Nankai earthquakes.
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Preliminary results from permanent GPS array by the Geological Survey of Japan in conjunction with Groundwater-level observations
Earth Planets and Space, 2000Co-Authors: Ryu Ohtani, Naoji Koizumi, Norio Matsumoto, Eikichi TsukudaAbstract:A regional continuous Global Positioning System (GPS) array, consisting of uniform antenna type, has been established by the Geological Survey of Japan (GSJ) mainly around the Kansai district. Geodetic results for 2.5 years data are as follows. In comparison with the solutions obtained from the Geographical Survey Institute (GSI) continuous GPS array which employs different type of antenna from the GSJ’s array, it was found that the agreements between the daily positions were about 10 mm in horizontal and 15 to 20 mm in vertical components. This result indicates that the influence of the antenna type difference is at this level. The GSJ’s GPS stations around the Kansai district were found to have a common annual variation in the vertical component, whose amplitude was different from site to site. There were small correlations with in situ measurements of Groundwater-level variation, except for the two stations whose annual variations of the GPS vertical component were the largest. The vertical displacements due to elastic deformation by Groundwater-Pressure changes in the aquifers were estimated using a simple model, but they were too small to account for the observed variations.
