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Toronto, Canada

Boivin A.,Carleton University | Boivin A.,Queens University | Lai P.,Carleton University | Samson C.,Carleton University | And 3 more authors.
Planetary and Space Science | Year: 2013

The Mars Methane Analogue Mission simulates a micro-rover mission whose purpose is to detect, analyze, and determine the source of methane emissions on the planet's surface. As part of this project, both an electromagnetic induction sounder (EMIS) and a high-resolution triangulation-based 3D laser scanner were tested at the Jeffrey open-pit asbestos mine to identify and characterize geological environments favourable to the occurrence of methane. The presence of serpentinite in the form of chrysotile (asbestos), magnesium carbonate, and iron oxyhydroxides make the mine a likely location for methane production. The EMIS clearly delineated the contacts between the two geological units found at the mine, peridotite and slate, which are separated by a shear zone. Both the peridotite and slate units have low and uniform apparent electrical conductivity and magnetic susceptibility, while the shear zone has much higher conductivity and susceptibility, with greater variability. The EMIS data were inverted and the resulting model captured lateral conductivity variations through the different bedrock geological units buried beneath a gravel road. The 3D point cloud data acquired by the laser scanner were fitted with triangular meshes where steeply dipping triangles were plotted in dark grey to accentuate discontinuities. The resulting images were further processed using Sobel edge detection to highlight networks of fractures which are potential pathways for methane seepage. © 2013 Elsevier B.V. All rights reserved. Source

Prinsenberg S.J.,Bedford Institute of Oceanography | Peterson I.K.,Bedford Institute of Oceanography | Holladay J.S.,Geosensors Inc. | Lalumiere L.,Sensors by Design Ltd.
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2011

This manuscript presents snow and ice properties collected in March 2009 of Lake Melville, a fjord located along the mid-Labrador coast. Ice thickness and ice roughness were collected with helicopter-borne Electromagnetic-laser (EM) sensor and snow thickness with a Ground-Penetrating-Radar (GPR) sensor. Lake Melville has freshwater surface layer due mainly to the outflow from the Churchill River, whose seasonal runoff cycle has been modified since 1972 by hydroelectric developments. The EM data indicated that the Lake's surface freshwater layer reached depths of up to 5m beneath a saline ice cover that varied in thickness between 50 and 150cm. The GPR measured snow thicknesses of up to 50cm, with thinner thicknesses near open water regions where the blowing snow was lost into the open water. Ice and snow property data collected at on-ice stations showed that the ice contained salt, suggesting it was formed from a saline surface mixed layer present when the ice was forming. A hand-lowered CTD, capable of going through a 2-inch auger hole in the ice, verified the existence of the winter surface freshwater layer. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE). Source

Monteiro Santos F.A.,University of Lisbon | Triantafilis J.,University of New South Wales | Taylor R.S.,Dualem Inc. | Holladay S.,Geosensors Inc. | Bruzgulis K.E.,University of New South Wales
Journal of Environmental and Engineering Geophysics | Year: 2010

In highly conductive environments the apparent electrical conductivity (σa) data generated from electromagnetic (EM) instruments are known to be non-linear. This is particularly the case when high conductivity bodies are present in the subsurface. However, little attention has been given to this issue in the research literature of the environmental and hydrological sciences. In this paper we describe the development of an inversion algorithm, which consists of a 1-D inversion with 2-D smoothness constraints between adjacent 1-D models, whereby the forward response is calculated using the full solution of the induction phenomena. The robustness of the algorithm is evaluated using σa data acquired from two study areas. In the first case study, σa data is acquired with a DUALEM-21 across a golf green in Guelph, Ontario Canada. In the second case study, a DUALEM-421 is used to collect σa across an irrigated field located on a clay alluvial plain of the Lower Gwydir Valley (Australia). The general patterns of modeled true electrical conductivity (σ), as achieved from our inversion algorithm with the full solution, are shown to compare favorably with the available information and existing knowledge at each site. We also find that the models calculated with the new algorithm compare favorably with those obtained using individual 1-D inversion. Source

Prinsenberg S.J.,Bedford Institute of Oceanography | Peterson I.K.,Bedford Institute of Oceanography | Holladay J.S.,Geosensors Inc. | Lalumiere L.,Sensors by Design Ltd.
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2012

During March 2009 and 2011, ice property data were collected from the mobile pack ice off the mid-Labrador coast with helicopter-borne sensors. The surveys collected ice thickness and roughness data with Electromagnetic-Laser (EM) system and overlapping-pictures with a Video-Laser system. The surveys in 2009 and 2011 covered the same offshore region and thus provide information on the inter-annual variability of the First Year pack ice properties. There are several overall pack ice differences between the near-normal winter of 2009 versus the warmer winter of 2011. From satellite imagery it can be seen that the ice extent was much less in the warmer winter of 2011 than in 2009. In addition, the helicopter-borne sensors data showed that mean and modal ice thicknesses of 2011 were much less than those of 2009, having a mean offshore ice thickness of 0.71m relative to 1.68m for 2009. The modal (most frequent occurring) ice thickness similarly decreased from 1.0-1.1m in 2009 to 0.6-0.7m in 2011. Thus ignoring ice extent, the ice volume off the mid-Labrador Shelf in 2011 due to ice thicknesses alone would be half of that present in 2009. The thinner ice and lower ice extent ice in 2011 can be explained by the fact that the 2011 winter was much warmer reducing regional ice growth as well as providing more heat to the offshore ocean which in turn also retards ice growth. In addition, westerly winds bringing the cold air to the region occurred less frequent during the winter of 2011, reducing the ice transport from the northern latitudes. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE). Source

Taylor R.S.,Dualem Inc. | Holladay J.S.,Geosensors Inc.
Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP | Year: 2011

Low-induction-number electromagnetic instruments have been used widely since the 1980s to measure apparent conductivity of the near surface. In 2010, an instrument incorporating 6 rigidly mounted arrays between 2-m and 6-m in length was developed to provide 6 simultaneous soundings of apparent conductivity. The depth of exploration of the deepest-sounding array is nominally 9 m. Where there is conductive layering of sufficient contrast and continuity within this depth range, estimates of layer conductivity and thickness can be made from the simultaneous data. Profiles of data were acquired across a previously mapped plume of leachate from a landfill at Canadian Forces Base Borden. Estimates of vadose-zone conductivity, saturated-zone conductivity and water-table depth derived from the EM data are in substantial agreement with well logs and samples. Source

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