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Near Surface 2007 - 13th EAGE European Meeting of Environmental and Engineering Geophysics
- Conference date: 03 Sep 2007 - 05 Sep 2007
- Location: Istanbul, Turkey
- ISBN: 978-90-73781-81-8
- Published: 03 September 2007
141 - 144 of 144 results
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Seismic Refraction Applied to Weathering Thickness Characterization and Slope Stability in NW Portugal
More LessIn the past decades urban areas have suffered large demographic pressures, forcing people and their housing compounds to migrate to peripheral regions were they often build without land planning concerns, and where many times they are subject to adverse natural conditions and exposed to natural hazards being landslides one of the main threats. Nowadays, geophysical methods assume a relevant role monitoring and surveying unstable slopes. We performed thirty seismic profiles with the aim of determine distribution of rock weathering through seismic refraction techniques, in Canelas, a small village in NW Portugal. Each profile was summarized with average values of velocity for each depth. Despite having a low density coverage for the area involved, the results seem to show that seismic refraction is an important tool to rapidly characterize weathering thicknesses, a very important factor to be taken into account in problems of slope stability.
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Resolution of Hydrostratigraphic Parameters from Inversions of HEM Measurements, Northern Bexar County, Texas
Authors A. Steuer, M. Deszcz-Pan and B.D. SmithHelicopter-borne electromagnetic (HEM) measurements were conducted in Bexar County, Texas, to map subsurface electrical resistivity distribution in order to better understand the geology and hydrology of the Cretaceous Edwards and Trinity (Glenn Rose Limestone) aquifers. These karstic aquifers are classified as sole-source aquifers and thus are critical to the water supply for the area, including the large metropolitan area of San Antonio. The Glen Rose is divided in an upper and lower zone. The upper zone is subdivided into five hydrostratigraphic intervals based on lithology and fossil content. The lower zone consists of more massive limestone deposits. The apparent resistivity map derived from the highest frequency HEM measurements correlate with the known outcropping hydrostratigraphic intervals. The HEM maps show that the intervals can be further divided into resistive (limestone) and relatively more conductive (mudstone) units. One particular area has been chosen for detailed study where the upper Glen Rose Limestone has been exposed in two drainages with a 30 m flat top hill (mesa) between them. Standard 1-D Marquardt-Levenberg inversions fail to resolve the extension beneath the mesa of resistive fossiliferous limestone exposed in the drainage. Laterally constrained inversion recovers a more realistic layered resistivity model.
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Subsidence Analysis in Mining Area of Dabrowskie Coal Basin using PSInSAR Technique
Authors A. Lesniak, S. Porzycka and M. GranicznyThe analysis of satellite data of Permanent Scatterers InSAR technique (PSInSAR) is presented in the paper. Presented discussion concern northeastern part of Upper Silesia, and supply information about slow, vertical ground movements, which occur there. Paper provides basic information connected with technique of the radar scenes processing (PSInSAR) and presents characteristics of the available PSInSAR data set. For detailed analysis of ground motions, revealed by PSInSAR technique, mining areas of Dabrowskie Coal Basin have been chosen. In order to find the reasons that could explain ground displacements in this region, the preliminary analysis of correlation between values of the ground movements rates, faults system and mining boundaries locations has been performed.
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Resistivity Imaging as a Tool for Rock Quarry Planning
Authors M. Arvidsson, T. Dahlin and J. FernlundIn the aggregate industry the use of geophysical measuring is rare. The aim of this project is to investigate how geophysical instruments can be a tool in prospecting for rock quarries, and also how they can be a help in which direction they should expand in. To have control over the quality of the aggregates is important and therefore to know when the rock mass is changing is of interest for the production. Two quarries, with different properties, were investigated with different geophysical methods, of which only the result from the electrical measurement is presented here. The fracture frequency was measured as well for comparison. The depth to the bedrock is visible in the inverted resistivity sections for the two sites, and an estimation of the quantity of the till is possible to make. It is also shown that the fracture frequency affects the resistivity of the bulk mass. The results also show that the resistivity imaging is well suited for detecting anomalies in the rock mass, which might affect the production.
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