Flooding, erosion, and increases in the water level in Lake Superior have contributed to changes in the stem location and width of the Grand Portage Creek. Those events threaten parts of the Grand Portage National Monument, a historically significant site on the North Shore of Lake Superior, Minnesota. We performed geophysical surveys to investigate these dynamic effects. We studied the near‐surface geological deposits, the mechanisms associated with creek stem dynamics, and sediment transport and deposition along the lakeshore in Grand Portage Bay. We deployed Ground Penetrating Radar (GPR), Sub Bottom Profiler (SBP), Side Scan Sonar (SSS), Geoprobe coring, and Van Veen Grab samplers and evaluated time‐lapse satellite images to assess the interaction of the Grand Portage Creek with the Grand Portage Bay. The onshore GPR surveys next to the national monument, the creek, and the shoreline showed the presence of a complex deposition with eroded ground surfaces and sediment layers across the creek valley. Results from the offshore geophysical campaigns and the interpretations of satellite images also document a heterogeneous deposition sequence environment with fine‐grained sediment deposits present south and southwest of the creek mouth. In addition, we documented an exposed boulder bed toward the east of the creek mouth that was exposed by the current and wave‐driven erosion process in the Grand Portage Bay. Time‐lapse satellite images and hydraulic current velocity simulations validate these observations and provide insight into how anthropogenic activities and natural events interact and might contribute to the long‐term stability of a site of historical and cultural importance.This article is protected by copyright. All rights reserved
{"title":"Geophysical surveys and satellite imaging for the evaluation of near‐surface terrain dynamic ‐ a case study on Grand Portage, MN, USA","authors":"Jeong-Mo Lee, D. Fratta","doi":"10.1002/nsg.12267","DOIUrl":"https://doi.org/10.1002/nsg.12267","url":null,"abstract":"Flooding, erosion, and increases in the water level in Lake Superior have contributed to changes in the stem location and width of the Grand Portage Creek. Those events threaten parts of the Grand Portage National Monument, a historically significant site on the North Shore of Lake Superior, Minnesota. We performed geophysical surveys to investigate these dynamic effects. We studied the near‐surface geological deposits, the mechanisms associated with creek stem dynamics, and sediment transport and deposition along the lakeshore in Grand Portage Bay. We deployed Ground Penetrating Radar (GPR), Sub Bottom Profiler (SBP), Side Scan Sonar (SSS), Geoprobe coring, and Van Veen Grab samplers and evaluated time‐lapse satellite images to assess the interaction of the Grand Portage Creek with the Grand Portage Bay. The onshore GPR surveys next to the national monument, the creek, and the shoreline showed the presence of a complex deposition with eroded ground surfaces and sediment layers across the creek valley. Results from the offshore geophysical campaigns and the interpretations of satellite images also document a heterogeneous deposition sequence environment with fine‐grained sediment deposits present south and southwest of the creek mouth. In addition, we documented an exposed boulder bed toward the east of the creek mouth that was exposed by the current and wave‐driven erosion process in the Grand Portage Bay. Time‐lapse satellite images and hydraulic current velocity simulations validate these observations and provide insight into how anthropogenic activities and natural events interact and might contribute to the long‐term stability of a site of historical and cultural importance.This article is protected by copyright. All rights reserved","PeriodicalId":49771,"journal":{"name":"Near Surface Geophysics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47364883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qingjie Yang, Bing Zhou, Marcus Engsig, M. Won, M. Riahi, M. Al-khaleel, S. Greenhalgh
Derivatives of the displacement tensor with respect to the independent model parameters of the subsurface, also called Fréchet derivatives (or sensitivity kernels), are a key ingredient for seismic full‐waveform inversion with a local‐search optimization algorithm. They provide a quantitative measure of the expected changes in the seismograms due to perturbations of the subsurface model parameters for a given survey geometry. Since 2.5‐D wavefield modeling involves a real point source in a 2‐D geological model with 3D (spherical) wave properties, it yields synthetic data much closer to the actual practical field data than the commonly used 2‐D wave simulation does, which uses an unrealistic line source in which the waves spread cylindrically. Based on our recently developed general 2.5‐D wavefield modeling scheme, we apply the perturbation method to obtain explicit analytic expressions for the derivatives of the displacement tensor for 2.5‐D/2‐D frequency‐domain seismic full‐waveform inversion in general viscoelastic anisotropic media. We then demonstrate the numerical calculations of all these derivatives in two common cases: (i) viscoelastic isotropic and (ii) viscoelastic tilted transversely isotropic (TTI) solids. Examples of the differing sensitivity patterns for the various derivatives are investigated and compared for four different homogeneous models involving 2‐D and 2.5‐D modeling. Also, the numerical results are verified against the analytic solutions for homogeneous models. We further validate the numerical derivatives in a 2‐D heterogeneous viscoelastic TTI case by conducting a synthetic data experiment of frequency‐domain full‐waveform inversion to individually recover the twelve independent model parameters (density, dip angle, five elastic moduli, and five corresponding Q‐factors) in a simple model comprising an anomalous square box target embedded in a uniform background. Another 2.5‐D multi‐target model experiment presenting impacts from four common seismic surveying geometries validates the Fréchet derivatives again.This article is protected by copyright. All rights reserved
{"title":"Numerical Fréchet derivatives of the displacement tensor for 2.5‐D frequency‐domain seismic full‐waveform inversion in viscoelastic TTI media","authors":"Qingjie Yang, Bing Zhou, Marcus Engsig, M. Won, M. Riahi, M. Al-khaleel, S. Greenhalgh","doi":"10.1002/nsg.12265","DOIUrl":"https://doi.org/10.1002/nsg.12265","url":null,"abstract":"Derivatives of the displacement tensor with respect to the independent model parameters of the subsurface, also called Fréchet derivatives (or sensitivity kernels), are a key ingredient for seismic full‐waveform inversion with a local‐search optimization algorithm. They provide a quantitative measure of the expected changes in the seismograms due to perturbations of the subsurface model parameters for a given survey geometry. Since 2.5‐D wavefield modeling involves a real point source in a 2‐D geological model with 3D (spherical) wave properties, it yields synthetic data much closer to the actual practical field data than the commonly used 2‐D wave simulation does, which uses an unrealistic line source in which the waves spread cylindrically. Based on our recently developed general 2.5‐D wavefield modeling scheme, we apply the perturbation method to obtain explicit analytic expressions for the derivatives of the displacement tensor for 2.5‐D/2‐D frequency‐domain seismic full‐waveform inversion in general viscoelastic anisotropic media. We then demonstrate the numerical calculations of all these derivatives in two common cases: (i) viscoelastic isotropic and (ii) viscoelastic tilted transversely isotropic (TTI) solids. Examples of the differing sensitivity patterns for the various derivatives are investigated and compared for four different homogeneous models involving 2‐D and 2.5‐D modeling. Also, the numerical results are verified against the analytic solutions for homogeneous models. We further validate the numerical derivatives in a 2‐D heterogeneous viscoelastic TTI case by conducting a synthetic data experiment of frequency‐domain full‐waveform inversion to individually recover the twelve independent model parameters (density, dip angle, five elastic moduli, and five corresponding Q‐factors) in a simple model comprising an anomalous square box target embedded in a uniform background. Another 2.5‐D multi‐target model experiment presenting impacts from four common seismic surveying geometries validates the Fréchet derivatives again.This article is protected by copyright. All rights reserved","PeriodicalId":49771,"journal":{"name":"Near Surface Geophysics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45142895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Glaciers generate seismic waves due to calving and fracturing, and recording and following event classification can be used to monitor glacier dynamics. Our aim with this study is to analyze seismic data acquired at the seabed and on land in front of Nordenskiöldbreen on Svalbard during 8 days in October 2020. The survey included 27 ocean bottom nodes, each equipped with three geophones and a hydrophone, and 101 land‐based geophones. The resulting data contain numerous seismic P‐, S‐, and Scholte wave events throughout the study period, as well as non‐seismic gravity waves. The recording quality strongly depends on receiver type and location, especially for the latter wave types. Our results demonstrate that hydrophones at the seabed are advantageous to record gravity waves, and that Scholte waves are only recorded close to the glacier. The Scholte waves are used to estimate the near‐surface S‐wave profile of the seabed sediments, and the gravity wave amplitudes are converted to wave height at the surface. We further discuss possible source mechanisms for the recorded events and present evidence that waves from earthquakes, calving, and brittle fracturing of the glacier and icebergs are all represented in the data. The interpretation is based on frequency content, duration, seismic velocities, and onset (emergent/impulsive), and supported by source localization which we show is challenging for this dataset. In conclusion, our study demonstrates the potential of using seismic for detecting glacier‐related events and provides valuable knowledge about the importance of survey geometry, particularly the advantages of including seabed receivers in the vicinity of the glacier.This article is protected by copyright. All rights reserved
{"title":"Case study of combined marine and land‐based passive seismic surveying in front of Nordenskiöldbreen outlet glacier, Adolfbukta, Svalbard","authors":"H. M. Stemland, B. Ruud, T. Johansen","doi":"10.1002/nsg.12266","DOIUrl":"https://doi.org/10.1002/nsg.12266","url":null,"abstract":"Glaciers generate seismic waves due to calving and fracturing, and recording and following event classification can be used to monitor glacier dynamics. Our aim with this study is to analyze seismic data acquired at the seabed and on land in front of Nordenskiöldbreen on Svalbard during 8 days in October 2020. The survey included 27 ocean bottom nodes, each equipped with three geophones and a hydrophone, and 101 land‐based geophones. The resulting data contain numerous seismic P‐, S‐, and Scholte wave events throughout the study period, as well as non‐seismic gravity waves. The recording quality strongly depends on receiver type and location, especially for the latter wave types. Our results demonstrate that hydrophones at the seabed are advantageous to record gravity waves, and that Scholte waves are only recorded close to the glacier. The Scholte waves are used to estimate the near‐surface S‐wave profile of the seabed sediments, and the gravity wave amplitudes are converted to wave height at the surface. We further discuss possible source mechanisms for the recorded events and present evidence that waves from earthquakes, calving, and brittle fracturing of the glacier and icebergs are all represented in the data. The interpretation is based on frequency content, duration, seismic velocities, and onset (emergent/impulsive), and supported by source localization which we show is challenging for this dataset. In conclusion, our study demonstrates the potential of using seismic for detecting glacier‐related events and provides valuable knowledge about the importance of survey geometry, particularly the advantages of including seabed receivers in the vicinity of the glacier.This article is protected by copyright. All rights reserved","PeriodicalId":49771,"journal":{"name":"Near Surface Geophysics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45638470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ground penetrating radar (GPR) is regulated regarding emission limits for ultra‐wideband (UWB) in a number of jurisdictions. The definitions of these regulations employ concepts and terminology that are more suited to traditional narrow band radio transmitters. Further, the emissions limits were based on limited quantitative factual information and have resulted in stringent limitations on GPR technology advancement. Factual theoretical and experimental information on the emissions from actual GPR devices is not generally available and the relationship with regulatory requirements is poorly understood by users. This information gap must be filled if a compelling argument for less stringent emissions levels is to be mounted in the future. Moreover, the current regulations have the potential to trigger further review of emission limits in the future which could be detrimental to the use of GPR. In this paper, we present the basic steps entailed in translating impulse time‐domain GPR instrument behaviour into ‘regulatory’ parameters. To achieve this, we also employ three‐dimensional (3D) finite‐difference time‐domain (FDTD) numerical modelling to simulate the transient electromagnetic (EM) field variation around dipole antennas placed on the surface of a half‐space or at a height over it to illustrate the dependency on sensor height and ground permittivity. The ultimate goal is to establish the foundation for more sensible rule making, if and when, the regulatory standards come under scrutiny for revision and further user understanding.This article is protected by copyright. All rights reserved
{"title":"Relating GPR System Parameters to Regulatory Emissions Limits","authors":"A. P. Annan, N. Diamanti, J. Redman","doi":"10.1002/nsg.12264","DOIUrl":"https://doi.org/10.1002/nsg.12264","url":null,"abstract":"Ground penetrating radar (GPR) is regulated regarding emission limits for ultra‐wideband (UWB) in a number of jurisdictions. The definitions of these regulations employ concepts and terminology that are more suited to traditional narrow band radio transmitters. Further, the emissions limits were based on limited quantitative factual information and have resulted in stringent limitations on GPR technology advancement. Factual theoretical and experimental information on the emissions from actual GPR devices is not generally available and the relationship with regulatory requirements is poorly understood by users. This information gap must be filled if a compelling argument for less stringent emissions levels is to be mounted in the future. Moreover, the current regulations have the potential to trigger further review of emission limits in the future which could be detrimental to the use of GPR. In this paper, we present the basic steps entailed in translating impulse time‐domain GPR instrument behaviour into ‘regulatory’ parameters. To achieve this, we also employ three‐dimensional (3D) finite‐difference time‐domain (FDTD) numerical modelling to simulate the transient electromagnetic (EM) field variation around dipole antennas placed on the surface of a half‐space or at a height over it to illustrate the dependency on sensor height and ground permittivity. The ultimate goal is to establish the foundation for more sensible rule making, if and when, the regulatory standards come under scrutiny for revision and further user understanding.This article is protected by copyright. All rights reserved","PeriodicalId":49771,"journal":{"name":"Near Surface Geophysics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46216476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. McLachlan, N. B. Christiensen, D. Grombacher, A. Christiansen
{"title":"Evaluating the impact of correlated noise for time‐lapse transient electromagnetic (TEM) monitoring studies","authors":"P. McLachlan, N. B. Christiensen, D. Grombacher, A. Christiansen","doi":"10.1002/nsg.12262","DOIUrl":"https://doi.org/10.1002/nsg.12262","url":null,"abstract":"","PeriodicalId":49771,"journal":{"name":"Near Surface Geophysics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41994944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A joint geophysical approach to tune an integrated sinkhole monitoring method in evaporitic environments","authors":"C. Calligaris, E. Forte, Alice Busetti, L. Zini","doi":"10.1002/nsg.12261","DOIUrl":"https://doi.org/10.1002/nsg.12261","url":null,"abstract":"","PeriodicalId":49771,"journal":{"name":"Near Surface Geophysics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49108671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Van Hong Nguyen, J. Germer, Nha Duong Van, F. Asch
{"title":"Soil resistivity measurements to evaluate subsoil salinity in rice production systems in the Vietnam Mekong Delta","authors":"Van Hong Nguyen, J. Germer, Nha Duong Van, F. Asch","doi":"10.1002/nsg.12260","DOIUrl":"https://doi.org/10.1002/nsg.12260","url":null,"abstract":"","PeriodicalId":49771,"journal":{"name":"Near Surface Geophysics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43823748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Resistivity and full‐decay IP inversion for imaging a coastal aquifer prone to saline intrusion: the Pontina Plain case study (Central Italy)","authors":"G. De Donno, M. Cercato","doi":"10.1002/nsg.12259","DOIUrl":"https://doi.org/10.1002/nsg.12259","url":null,"abstract":"","PeriodicalId":49771,"journal":{"name":"Near Surface Geophysics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43501678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Stiffness evolution of jet grouting columns performed under port caissons using PS suspension logging","authors":"Á. Tijera, E. Asanza, R. Galindo, Marcelo Burgos","doi":"10.1002/nsg.12258","DOIUrl":"https://doi.org/10.1002/nsg.12258","url":null,"abstract":"","PeriodicalId":49771,"journal":{"name":"Near Surface Geophysics","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2023-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47721169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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