scholarly journals Study of riverine deposits using electromagnetic methods at a low induction number

Geophysics ◽  
2007 ◽  
Vol 72 (5) ◽  
pp. B113-B120 ◽  
Author(s):  
Luigi Sambuelli ◽  
Salvatore Leggieri ◽  
Corrado Calzoni ◽  
Chiara Porporato
Keyword(s):  
Po River ◽  
Sampling Campaign ◽  
Electromagnetic Methods ◽  
Direct Sampling ◽  
Global Positioning ◽  
Ground Penetrating ◽  
Text Signal ◽  
Time Domain Reflectometer ◽  
Depth Of Investigation ◽  
River Bottom

We conducted electromagnetic (EM) profiles along the Po River in Turin, Italy. The aim of this activity was to verify the applicability of low-induction-number EM multifrequency soundings carried out from a boat in riverine surveys and to determine whether this technique, which is cheaper than air-carried surveys, could be used effectively to define the typology of sediments and to estimate the stratigraphy below a riverbed. We used a GEM-2 handheld broadband EM sensor operating with six frequencies to survey the investigated area. Ground-penetrating radar (GPR), a conductivity meter, and a time-domain reflectometer were used to estimate the bathymetry and to measure the EM properties of the water. A global positioning system, working in real-time kinematic mode, tracked the route of the boat with centimetric accuracy. We analyzed the induction number, the depth of investigation (DOI), and the sensitivity of our experimental setup by forward modeling — varying the water depth, frequency, and bottom-sediment resistivity. The simulations optimized the choice of the frequencies that could be used reliably for the interpretation. The [Formula: see text] signal had a DOI in the Po River water [Formula: see text] of [Formula: see text] and provided sediment resistivities higher than [Formula: see text]. We applied a bathymetric correction to the conductivity data using the water depths obtained from the GPR data. We plotted a map of the river bottom resistivity and compared this map to the results of a direct sediment sampling campaign. The resistivity values [Formula: see text] were compatible with the saturated gravel and pebbles in a sandy matrix, which resulted from direct sampling and with the known geology.

scholarly journals Waterborne GPR survey for estimating bottom-sediment variability: A survey on the Po River, Turin, Italy

Geophysics ◽  
2009 ◽  
Vol 74 (4) ◽  
pp. B95-B102 ◽  
Author(s):  
Luigi Sambuelli ◽  
Corrado Calzoni ◽  
Manuele Pesenti
Keyword(s):  
Geophysical Survey ◽  
Amplitude Ratios ◽  
Water Conductivity ◽  
Po River ◽  
Sampling Campaign ◽  
Riverbed Sediments ◽  
Direct Sampling ◽  
Integrated Geophysical Survey ◽  
River Po ◽  
Sediment Variability

We conducted an integrated geophysical survey on a stretch of the river Po in order to check the GPR ability to discriminate the variability of riverbed sediments through an analysis of the bottom reflection amplitudes. We conducted continuous profiles with a [Formula: see text] GPR system and a handheld broadband EM sensor. A conductivity meter and a TDR provided punctual measurements of water conductivity, permittivity, and temperature. The processing and interpretation of the GEM-2 and GPR data were enhanced by reciprocal results and by integration with the punctual measurements of the EM properties of the water. We used a processing flow that improved the radargram images and preserved the amplitude ratios among the different profiles and the frequency content at the bottom reflection signal. We derived the water attenuation coefficient both from the punctual measurements using the Maxwell formulas and from the interpretation of the GPR data, finding an optimal matching between the two values. The GPR measurements provided maps of the bathymetry and of the bottom reflection amplitude. The high reflectivity of the riverbed, derived from the GPR interpretation, agreed with the results of the direct sampling campaign that followed the geophysical survey. The variability of the bottom-reflection-amplitudes map, which was not confirmed by the direct sampling, could also have been caused by scattering phenomena due to the riverbed clasts which are dimensionally comparable to the wavelength of the radar pulse.

scholarly journals Ground-water intrusions in a mine beneath Høganesbreen, Svalbard: assessing the possibility of evacuating water subglacially

2003 ◽  
Vol 37 ◽  
pp. 269-274 ◽  
Author(s):  
Kjetil Melvold ◽  
Thomas Schuler ◽  
Gaute Lappegard
Keyword(s):  
Ground Water ◽  
Drainage System ◽  
Hot Water ◽  
Measured Temperature ◽  
System A ◽  
Basal Ice ◽  
Global Positioning ◽  
Pressure Melting ◽  
Ground Penetrating ◽  
The Given

AbstractEvacuation of the ground-water intruding into a coal mine beneath Høganesbreen, Svalbard, is difficult and expensive. To solve this problem, it was proposed that the mine be connected to the ice–bedrock interface. Pumping hot water from the mine should establish a flow path along the glacier bed where the ground-water would drain gravitationally. In this paper, we assess the requirements for maintaining such a drainage system in open-channel conditions. To obtain the bedrock topography, we determined the ice thickness by ground-penetrating radar and subtracted it from the surface elevation measured by global positioning system. A measured temperature profile at the site where the mine should connect to the glacier bed (140m depth) revealed that the basal ice is below the pressure-melting point. The locations of major subglacial conduits were estimated using a hydraulic-potential approach. We adopted a model oftime-dependent discharge through a Röthlisberger channel to calculate a set of scenarios using different flow-law parameters. Results of the simulations suggest that for the given conditions, water flow would be pressurized, thereby inhibiting the gravitational drainage of the mine.

scholarly journals Improved Measurements and Analysis of Spatial Snow Cover by Combining a Ground Based Radar System With a Differential Global Positioning System Receiver

2001 ◽  
Vol 32 (3) ◽  
pp. 181-194 ◽  
Author(s):  
Wolf-Dietrich Marchand ◽  
Oddbjørn Bruland ◽  
Ånund Killingtveit
Keyword(s):  
Snow Cover ◽  
Global Positioning System ◽  
Snow Depth ◽  
Control Unit ◽  
Snow Accumulation ◽  
Positioning System ◽  
Global Positioning ◽  
Log File ◽  
Ground Penetrating ◽  
Differential Global Positioning System

The paper describes the realization of a new snow measurement system where a Ground Penetrating Radar (GPR) is connected to a Differential Global Positioning System (DGPS) receiver. A snow scooter pulled a radar antenna, a distance wheel triggered the radar pulses and the reflections were stored in a control unit. A marker was set on the radar file each time a position was logged on the DGPS receiver. Thus, each position was directly related to a snow depth measured by the GPR. The obtained accuracy of the position was in the range of 5-10 m and manual calibration measurements were used to ensure good quality of the snow depth data. The system was tested in the Norwegian catchment Aursunden during the period of maximum snow accumulation, 12th – 23rd April 1999. Landscape features were analyzed with a Geographic Information System (GIS) and extensive snow measurements were worked out in representative areas. The obtained data on the snow cover were later used for statistical analysis. In addition to the efficiency which makes it possible to measure large areas in a relatively short time, the major advances in the described system is that the obtained data can be used directly in a computer aided GIS. Nevertheless, further improvement is needed because of 1) the possibility for ambiguous connection between snow depth log and position log, 2) the distance between consecutive positions is not constant since it is time dependent, 3) the algorithm for automatically detection of the ground reflection from the radar log-file still needs interference from the user.

ESTIMATES OF SOIL WATER CONTENT USING GROUND-PENETRATING RADAR IN FIELD CONDITIONS

2016 ◽  
Vol 33 (3) ◽  
Author(s):  
Marcelo Jorge Luz Mesquita ◽  
José Gouvêa Luiz ◽  
José de Paulo Rocha da Costa
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Ground Penetrating Radar ◽  
Field Conditions ◽  
Electromagnetic Properties ◽  
Shallow Subsurface ◽  
Electromagnetic Methods ◽  
Ground Penetrating

ABSTRACT. Electromagnetic methods play an important role in the study of soil water content, mainly because electromagnetic properties in the shallow subsurface area are primarily controlled by the presence of... RESUMO. Os métodos eletromagnéticos são uma importante ferramenta no estudo da umidade do solo, principalmente porque as propriedades eletromagnéticas da subsuperfície rasa são...

Stratigraphic mapping of sedimentary formations in southern Ontario by ground electromagnetic methods

Geophysics ◽  
1990 ◽  
Vol 55 (9) ◽  
pp. 1148-1157 ◽  
Author(s):  
Ajit K. Sinha
Keyword(s):  
Oil And Gas ◽  
Structural Features ◽  
Southern Ontario ◽  
Transient Electromagnetic ◽  
Electromagnetic Methods ◽  
Geological Information ◽  
Survey Results ◽  
Multifrequency System ◽  
The Village ◽  
Depth Of Investigation

Multifrequency and transient electromagnetic (EM) soundings were done at several locations in southern Ontario to evaluate the possibility of stratigraphic mapping of gently dipping sedimentary formations by ground EM techniques. The possibility of detecting structural features such as folds, faults, and grabens in the formations was also explored. The two EM techniques were used to map a buried river valley near the village of Copetown, about 75 km southwest of Toronto. The valley, buried under fairly resistive glacial till and dolomite formations was mapped at depths ranging from 100 to 200 m. The interpreted shape and depth of the valley agreed well with information from a high resolution seismic reflection survey and data from wells penetrating the bedrock. Transient EM (TEM) data, using square transmitter loops with side dimensions comparable to the transmitter‐receiver separation for the multifrequency system, was found to be less affected by the presence of shallow conductors and lateral inhomogeneities than the multifrequency data, and had greater depth of investigation. TEM soundings were made on five additional profiles in the area. Lithologic logs from old oil and gas wells located near the profiles provided information for comparison with EM sounding interpretations. The depths to various dolomite, shale, and limestone formations interpreted from EM data agreed well with drillhole information. The EM soundings also detected structures in the Paleozoic formations such as faults and folds that were not previously known. The soundings confirmed the existence of a graben at one site at a depth of 100 m, which was postulated from logs from a cluster of closely spaced drillholes by geologists. The survey results indicated that EM sounding methods can be used for stratigraphic mapping in areas where detailed geological information is unavailable either because the bedrock is concealed by overburden, or when drillholes are sparsely distributed.

scholarly journals High resolution electromagnetic methods and low frequency dispersion of rock conductivity

1999 ◽  
Vol 42 (4) ◽  
Author(s):  
B. S. Svetov ◽  
V. V. Ageev
Keyword(s):  
High Resolution ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Electromagnetic Methods ◽  
Near Zone ◽  
Vertical Magnetic Dipole ◽  
Time Domains ◽  
Debye Formula ◽  
Wave Phenomena ◽  
Depth Of Investigation

The influence of frequency dispersion of conductivity (induced polarization) of rocks on the results of electromagnetic (EM) sounding was studied on the basis of calculation of electric field of vertical magnetic dipole above horizontally layered polarizable sections. Frequency dispersion was approximated by the Debye formula. Polarizable homogeneous halfspace, two, three and multilayered sections were analyzed in frequency and time domains. The calculations for different values of chargeability and time constants of polarization were performed. In the far zone of a source, the IP of rocks led to quasi-wave phenomena. They produced rapid fluctuations of frequency and transient sounding curves (interference phenomena, multireflections in polarizable layers). In the case of transient sounding in the near zone of a source quasistatic distortions prevailed, caused by the counter electromotive force arising in polarizable layers which may lead to strong changes in transient curves. In some cases quasiwave and quasistatic phenomena made EM sounding curves non-interpretable in the class of quasistationary curves over non-dispersive sections. On the other hand, they could increase the resolution and depth of investigation of EM sounding. This was confirmed by an experience of "high-resolution" electroprospecting in Russia. The problem of interpretation of EM sounding data in polarizable sections is nonunique. To achieve uniqueness it is probably necessary to complement them by soundings of other type.

Ground‐penetrating radar responses of dispersive models

Geophysics ◽  
1997 ◽  
Vol 62 (4) ◽  
pp. 1127-1131 ◽  
Author(s):  
Zonghou Xiong ◽  
Alan C. Tripp
Keyword(s):  
Environmental Management ◽  
Electrical Properties ◽  
Ground Penetrating Radar ◽  
Dispersive Media ◽  
Efficient Tool ◽  
Target Region ◽  
High Frequencies ◽  
Ground Penetrating ◽  
Dispersive Models ◽  
Depth Of Investigation

Ground‐penetrating radar (GPR) has been a very efficient tool for mapping shallow targets for applications such as those in geological engineering and environmental management (Fisher et al. 1992). Since the application of GPR depends on the complex electrical properties of the ground, it is important to study this dependence in all its manifestations. The depth of investigation for GPR applications depends strongly on the conductivity of the ground. If the ground is very conductive, GPR waves will be absorbed before they reach the target region. Earth materials can be dispersive, i.e., the conductivity and permittivity of rocks are frequency dependent (Levitskaya and Sternberg, 1994). This is especially true at high frequencies. GPR waves will also be absorbed in dispersive media. Hence modeling the GPR response in dispersive materials can reveal behaviors of importance in understanding field responses.

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