Detection of the near surface structure through a multidisciplinary geophysical approach

2011 ◽  
Vol 3 (4) ◽  
Author(s):  
Eleni Kokinou ◽  
Apostolos Sarris
Keyword(s):  
Seismic Refraction ◽  
Geophysical Methods ◽  
Near Surface ◽  
The Road ◽  
Resistivity Method ◽  
Conductivity Anomalies ◽  
2D Resistivity Imaging ◽  
Limestone Rock ◽  
Ground Penetrating ◽  
2D Resistivity

AbstractThe present survey aimed to image the subsurface structure, including karstic voids, and to evaluate the extent of the heterogeneities that can result in potentially dangerous collapse of road segments overlying these features. A multidisciplinary geophysical approach (seismic refraction, frequency domain electromagnetic and ground penetrating radar) in combination with a detailed geological survey indicated the presence of tectonic faults as well as velocity and conductivity anomalies along an old road within the area of Akrotiri at Chania (Crete). Due to the presence of subsurface fuel pipes, perpendicular to the direction of the road, 2D resistivity imaging was excluded from the applied geophysical methods.Interpretation of the geophysical data revealed that the section of the road investigated overlies prominent voids attributed mostly to karst features. The conductivity and velocity anomalies are interpreted to indicate an area where the host limestone rock has been downthrown by faulting and associated karstification. The continuation of this fault zone was observed in the slope of the road during later excavations. Interpretation, using geographic information systems (GIS) to integrate data, allowed these controls and relationships to be understood and monitored. The above methodology was proved successful for areas where the application of resistivity method is not possible.

scholarly journals Multi-Parametric Imaging of Etruscan Chamber Tombs: Grotte Di Castro Case Study (Italy)

2021 ◽  
Vol 11 (17) ◽  
pp. 7875
Author(s):  
Vincenzo Sapia ◽  
Valerio Materni ◽  
Federico Florindo ◽  
Marco Marchetti ◽  
Andrea Gasparini ◽  
...  
Keyword(s):  
Geophysical Methods ◽  
Geochemical Data ◽  
Distribution Data ◽  
Resistivity Tomography ◽  
Resistivity Method ◽  
Method Integration ◽  
Radar Measurements ◽  
Soil Measurements ◽  
Ground Penetrating

A multi-parametric approach that involves the use of different geophysical methods coupled with geochemical data allowed us to identify undiscovered archeological burials in a funerary area of the Grotte di Castro Etruscan settlement. In particular, we tested the suitability of the capacitive resistivity method and the presence of Radon in soil for the identification of burials calibrating their outcomes over coincident survey profiles with standard geophysical techniques routinely applied for archaeological prospections. Soil Radon data were acquired both in a grid and along a profile to highlight anomalous gas concentrations, whereas electrical resistivity and ground-penetrating radar measurements were conducted on overlapping profiles to depict the electrical and electromagnetic subsurface distribution. Data integration showed a series of anomalies, suggesting the presence of multiple burials starting from a depth of approximately 1.5 m below the terrain surface. Slight anomalies of Radon in the soil were found to correspond to most of the recovered geophysical ones. Our results pointed out the effectiveness of geophysical method integration in archeological prospecting with the novelty of the joint use of Radon in soil measurements and capacitive resistivity tomography. The latter provided reliable results and can be considered as a standalone technique in archaeological surveys.

Effectiveness of Geophysical Methods in Calcareous Harbor Fills

2013 ◽  
Author(s):  
Horst G. Brandes
Keyword(s):  
Ground Penetrating Radar ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Fill Material ◽  
Object Locations ◽  
Ground Penetrating

The effectiveness of electromagnetic (EM), ground penetrating radar (GPR) and seismic refraction (SR) were evaluated by surveying a shallow trench in which a number of objects of varying composition and size were buried. The trench was excavated in granular calcareous fill material. An experienced geophysical contractor was asked to provide blind predictions of object locations using each of the techniques in turn. GPR with a 400 MHz antenna was the most successful, followed by SR and EM surveying. GPR and SR were also carried out at the port of Hilo to investigate complex subsurface conditions.

Geophysical characterization of inactive/active rock glaciers in the semi-arid Andes using seismic, geoelectrics and GPR

2020 ◽  
Author(s):  
remi valois ◽  
Nicole Schafer ◽  
Giulia De Pasquale ◽  
Gonzalo Navarro ◽  
Shelley MacDonell
Keyword(s):  
Electrical Resistivity ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Late Summer ◽  
Relevant Information ◽  
Refraction Tomography ◽  
Rock Glaciers ◽  
Ice Content ◽  
Ground Penetrating

<p>Rock glaciers play an important hydrological role in the semiarid Andes (SA; 27º-35ºS). They cover about three times the area of uncovered glaciers and they are an important contribution to streamflow when water is needed most, especially during dry years and in the late summer months. Their characteristics such as their extension in depth and their ice content is poorly known. Here, we present a case study of one active rock glacier and periglacial inactive geoform in Estero Derecho (~30˚S), in the upper Elqui River catchment, Chile. Three geophysical methods (ground-penetrating radar and electrical resistivity and seismic refraction tomography) were combined to detect the presence of ice and understand the internal structure of the landform. The results suggest that the combination of electrical resistivity and seismic velocity provide relevant information on ice presence and their geometry. Radargrams shows diffraction linked to boulders presence but some information regarding electromagnetic velocity could be extracted. These results strongly suggest that such landforms contain ice, are therefore important to include in future inventories and should be considered when evaluating the hydrological importance of a particular region.</p><p> </p>

scholarly journals Landslide investigations using the geoelectrical scanning method and ground penetrating radar: Case studies

Tehnika ◽  
2021 ◽  
Vol 76 (4) ◽  
pp. 419-425
Author(s):  
Filip Arnaut ◽  
Branislav Sretenović
Keyword(s):  
Ground Penetrating Radar ◽  
Geophysical Methods ◽  
Relevant Information ◽  
Electromagnetic Signal ◽  
Near Surface ◽  
Scanning Method ◽  
Low Resistivity ◽  
Geotechnical Investigations ◽  
Landslide Body ◽  
Ground Penetrating

Geotechnical investigations of landslides for future mitigation are a complex task. To obtain relevant information, various geophysical methods are used, with varying degrees of success. The geoelectrical scanning method, also known as Electrical Resistivity Tomography (ERT) has been successfully applied in several locations in Serbia in the las three decades. The geoelectrical scanning method was used during investigations of landslides: Umka, Lukovska banja, Tara, and Trandžament, while both geoelectrical scanning and Ground Penetrating Radar (GPR) were utilized at the Trandžament landslide. The achieved results from both methods are mutually correlated at the Trandžament landslide. Correlation of GPR data with geoelectrical scanning data was only possible since there were no nearsurface low resistivity zones in the Trandžament landslide body. Otherwise, electromagnetic signal attenuation would be high in the presence of near-surface low resistivity zones, and a quality signal would be impossible to detect at the receiving antenna.

scholarly journals An Investigation of Groundwater Contamination around Nsukka Municipality Dumpsite using the Resistivity Method

2020 ◽  
Author(s):  
Olisah Nzemeka
Keyword(s):  
Electrical Resistivity ◽  
Groundwater Contamination ◽  
Low Resistivity ◽  
Electrical Resistivity Survey ◽  
Resistivity Method ◽  
Electrical Sounding ◽  
On Line ◽  
2D Resistivity Imaging ◽  
Resistivity Meter ◽  
2D Resistivity

An investigation using electrical resistivity method was conducted around a solid waste dumpsite at Nsukka in Nsukka L.G.A of Enugu State, Nigeria to investigate the level of groundwater contamination. Electrical Sounding (VES) and 2D resistivity imaging were used with a digital read out resistivity meter (ABEM SAS 1000) to acquire data in the area. A total of eight (8) sounding and six (6) 2D resistivity imagings were carried out in the area. A contaminant leachate plume was delineated in 2D resistivity sections as low resistivity zones while the VES shows the depth of aquifer. In 2D pseudosections where bluish colours with low resistivities (less than 20.80Ωm) with the depth ranging from 1.28m to 17.1m in the Line 1 and 2 are seen as contaminated zones. The rest of the lines are not contaminated because of their high resistivities (greater than 20.80Ωm). The result of the electrical resistivity survey also showed 4 - 5 layers geo-electric sections and an AA and AK type sounding curves. The VES result shows that VES 1A, 1B, 2A and 2B which are carried out on line 1 & 2 of the wenner lines showed signs of contamination with low resistivity values less than 20.80Ωm complementing the wenner results. The contamination has not yet got to where the aquifer is located on the lines. Since the depth to the aquifer ranges from 30.26m to 155.43m while maximum depth of contamination is 17.1m. It is believed that the leachate has not percolated down to the aquiferous zones as such aquifers are presumed to be free.

Localization of Deep Voids through Geophysical Signatures of Secondary Dewatering Features

Geophysics ◽  
2021 ◽  
pp. 1-81
Author(s):  
Dan R. Glaser ◽  
Katrina Burch ◽  
Dennis L. Brinkley ◽  
Philip Reppert
Keyword(s):  
Seismic Refraction ◽  
Geophysical Methods ◽  
Mixing Model ◽  
Time Domain Reflectometry ◽  
Groundwater Table ◽  
Void Space ◽  
Investigation Area ◽  
Measurement Geometry ◽  
Lateral Localization ◽  
Ground Penetrating

Discrete deep targets are a significant challenge for most surface-based geophysical techniques, even when considering high property contrasts. Generally, surface-based geophysical methods lose lateral and vertical resolution with depth as a result of poor measurement geometry and increased signal attenuation. The poor measurement geometry can be overcome through use of cross-borehole methods, but lateral localization is still needed for optimal borehole placement. As such, a relatively small, deep void located near the maximum depth of investigation is very unlikely to be detected. Yet, secondary features associated with these voids can be exploited for enhanced detection performance. When voids are located below the groundwater table a significant amount of dewatering and pumping is required to make them a functional passageway. This dewatering not only removes water from the void space but also the surrounding formation, resulting in a much larger, if more diffuse, secondary target: an induced groundwater table gradient. Many geophysical sensing methods are sensitive to subsurface moisture content. Here we implement a two-dimensional (2D) joint-petrophysical mixing-model, using inverted electrical resistivity tomography and inverted seismic refraction models to sense changes in the groundwater table gradient. Results are validated using depth to bedrock, groundwater-surface water information, ground-penetrating radar, and time-domain reflectometry methods. Our initial proof of concept is applied to a shallow area with a significant soil moisture gradient, through different surface soil types and bedrock. The 2D joint-petrophysical mixing-model results were used to generate an estimate of air, moisture, and matrix percent fractions in the investigation area, providing a clear delineation of the groundwater surface.

Efficiency Of Integrated Seismic Methods Approach To Near-Surface Characterization

2020 ◽  
Author(s):  
Irena Gjorgjeska ◽  
Vlatko Sheshov ◽  
Kemal Edip ◽  
Dragi Dojchinovski
Keyword(s):  
Surface Characterization ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Cost Effective ◽  
Integrated Approach ◽  
Image Resolution ◽  
Future Research ◽  
Near Surface ◽  
Seismic Methods ◽  
Refraction Seismic

<p>Surface seismic methods are among the most popular, widely accepted, geophysical methods for near-surface characterization. The most practical and effective way to perform in-situ measurements and data processing using different seismic methods as are seismic refraction, seismic reflection and MASW method in an integrated approach is presented in this paper. Each method has some advantages and limitations, but their application in an integrated approach provides higher accuracy in subsurface modeling. The same seismic equipment and, in most of the cases, the same acquisition parameters were used, enabling time and cost effective survey for subsurface characterization. The choice of these parameters was not random. Experimental research by use of the above-mentioned seismic methods was carried out in a long period in order to define the optimal parameters for successful application of an integrated technique in future research. During this survey, particular attention was paid to the influence of the acquisition parameters on the dispersion image resolution in the MASW surveys and extraction of an effective dispersion curve.</p><p>The results of the performed surveys at characteristic locations in R. North Macedonia are presented to show the efficiency of the combined methods approach.</p>

Détermination de la géométrie et des propriétés physiques du pergélisol discontinu de la région de Schefferville

1977 ◽  
Vol 14 (3) ◽  
pp. 431-443 ◽  
Author(s):  
Maurice K.-Seguin
Keyword(s):  
Electrical Resistivity ◽  
Regional Scale ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Near Surface ◽  
Vertical Extension ◽  
Discontinuous Permafrost ◽  
Propriétés Physiques ◽  
Lower Limits

The various parameters used to predict on a regional scale the lateral and vertical extension of permafrost are the following: surface temperature, thermal conductivity of rocks, and geothermal flow configuration. Locally this type of data is generally not sufficient and far too inaccurate. The use of geophysical methods at the surface and in boreholes in addition to existing thermal data helps to improve the degree of accuracy in the prediction of spatial distribution of permafrost in a given area. These geophysical methods include seismic refraction, electrical resistivity, and spontaneous and induced polarizations.Because of the properties of permafrost, seismic refraction at surface is useful only to determine the top of the permafrost whereas electrical resistivity (electric logging near surface) allows the determination of the upper and lower limits of permafrost. Seismic refraction, resistivity, and spontaneous and induced polarizations in boreholes were deemed more promising to determine masses or lenses of permafrost.Moreover, it was possible to correlate temperature and electrical resistivity measurements in boreholes, thus allowing the drawing of isothermal curves from electric logging in areas of continuous and discontinuous permafrost, at least when it is 'marginal'.The data for this study were obtained from the experimental station at Schefferville, Québec. [Journal Translation]

Uncertainties Analysis of Electrical Resistivity Tomography

2021 ◽  
Author(s):  
Yonatan Garkebo Doyoro ◽  
Chang Ping-Yu ◽  
Jordi Mahardika Puntu
Keyword(s):  
Model Resolution ◽  
Resistivity Data ◽  
Resistivity Method ◽  
Resistivity Model ◽  
2D Resistivity Imaging ◽  
Model Set ◽  
Different Depths ◽  
Measured Resistivity ◽  
2D Resistivity ◽  
Subsurface Cavities

<p>We examined the uncertainty of the resistivity method in cavity studies using a synthetic cavity model set at six-different depths. Conceptual models were simulated to generate synthetic resistivity data for dipole-dipole, pole-dipole, Wenner-Schlumberger, and pole-pole arrays. The 2D geoelectric models were recovered from the inversion of the synthetically measured resistivity data. The highest anomaly effect (1.46) and variance (24400) in resistivity data were recovered by dipole-dipole array, while the pole-pole array obtained the lowest anomaly effect (0.60) and variance (2401) for the target cavity T<sub>1</sub>. The anomaly effect and variance were linearly associated with the quality of the inverted models. The steeper anomaly gradient of resistivity indicated more distinct cavity boundaries, while the gentler gradient prevents the inference of the cavity boundaries. The recovered model zone above the depth of investigation index of 0.1 has shown relatively higher sensitivity. Modeling for dipole-dipole array provided the highest model resolution and anomaly gradient that shows a relatively distinct geometry of the cavity anomalies. On the contrary, the pole-dipole and Wenner-Schlumberger arrays recovered good model resolutions and moderate anomaly gradient but determining the anomaly geometries is relatively challenging. Whereas, the pole-pole array depicted the lowest model resolution and anomaly gradient with less clear geometry of the cavity anomalies. At deeper depths, the inverted models showed a reduction in model resolutions, overestimation in anomaly sizes, and deviation in anomaly positions, which can create ambiguity in resistivity model interpretations. Despite these uncertainties, our modeling specified that the 2D resistivity imaging is a potential technique to study subsurface cavities.</p>

Sign in / Sign up

Export Citation Format

Share Document