Full-resolution 3D GPR imaging

Geophysics ◽  
2005 ◽  
Vol 70 (1) ◽  
pp. K12-K19 ◽  
Author(s):  
Mark Grasmueck ◽  
Ralf Weger ◽  
Heinrich Horstmeyer
Keyword(s):  
Fractured Rock ◽  
Test Site ◽  
Spatial Sampling ◽  
Minimum Requirement ◽  
Shallow Subsurface ◽  
Full Resolution ◽  
Half Wavelength ◽  
Quarter Wavelength ◽  
3D Gpr ◽  
Fractured Limestone

Noninvasive 3D ground-penetrating radar (GPR) imaging with submeter resolution in all directions delineates the internal architecture and processes of the shallow subsurface. Full-resolution imaging requires unaliased recording of reflections and diffractions coupled with 3D migration processing. The GPR practitioner can easily determine necessary acquisition trace spacing on a frequency-wavenumber (f-k) plot of a representative 2D GPR test profile. Quarter-wavelength spatial sampling is a minimum requirement for full-resolution GPR recording. An intensely fractured limestone quarry serves as a test site for a 100-MHz 3D GPR survey with 0.1 m × 0.2 m trace spacing. This example clearly defines the geometry of fractures in four different orientations, including vertical dips to a depth of 20 m. Decimation to commonly used half-wavelength spatial sampling or only 2D migration processing makes most fractures invisible. The extra data-acquisition effort results in image volumes with submeter resolution, both in the vertical and horizontal directions. Such 3D data sets accurately image fractured rock, sedimentary structures, and archeological remains in previously unseen detail. This makes full-resolution 3D GPR imaging a valuable tool for integrated studies of the shallow subsurface.

A Dual-Band Comb-Line Filter Using a Half-Wavelength Stripline Nesting a Quarter-Wavelength Coplanar Waveguide Resonator

2007 ◽  
Vol E90-B (9) ◽  
pp. 2439-2446 ◽  
Author(s):  
S. KITAZAWA ◽  
M. GESHIRO ◽  
K. ISHIMARU ◽  
M. OHASHI ◽  
H. FUJIMOTO ◽  
...  
Keyword(s):  
Coplanar Waveguide ◽  
Dual Band ◽  
Waveguide Resonator ◽  
Half Wavelength ◽  
Quarter Wavelength

Building Confidence in Radionuclide Transport Models for Fractured Rock: The Nagra/JNC Radionuclide Retardation Programme

2000 ◽  
Vol 663 ◽  
Author(s):  
K. Ota ◽  
W.R. Alexander ◽  
P.A. Smith ◽  
A. Möri ◽  
B. Frieg ◽  
...  
Keyword(s):  
Fractured Rock ◽  
Test Site ◽  
Process Models ◽  
Swiss Alps ◽  
Radionuclide Transport ◽  
Transport Models ◽  
North East ◽  
Host Rocks ◽  
Experimental Technology

ABSTRACTThe joint Nagra/JNC Radionuclide Retardation Programme has now been ongoing for 15 years with the main aim of direct testing of radionuclide transport models in as realistic a manner as possible. A large programme of field, laboratory and natural analogue studies has been carried out at the Grimsel Test Site in the central Swiss Alps and the Kamaishi In Situ Test Site in north-east Japan. The understanding and modelling of both the processes and the structures influencing radionuclide transport/retardation in fractured host rocks have matured as has the experimental technology, which has contributed to develop confidence in the applicability of the underlying research models in a repository performance assessment. In this paper, the successes and set-backs of this programme are discussed as is the general approach to the thorough testing of the process models and of model assumptions. In addition, a set of key findings is presented, involving discussions on the enhancement of confidence through the program.

scholarly journals Borehole temperature log from the Glasgow Geothermal Energy Research Field Site: a record of past changes to ground surface temperature caused by urban development

2020 ◽  
Vol 56 (2) ◽  
pp. 134-152 ◽  
Author(s):  
Sean M. Watson ◽  
Rob Westaway
Keyword(s):  
Heat Flow ◽  
Urban Development ◽  
Coal Mining ◽  
Industrial Revolution ◽  
Test Site ◽  
Research Field ◽  
Geothermal Heat ◽  
Surface Warming ◽  
Shallow Subsurface ◽  
History Of

As part of the Glasgow Geothermal Energy Research Field Site (GGERFS) project, intended as a test site for mine-water geothermal heat, the GGC-01 borehole was drilled in the Dalmarnock area in the east of the city of Glasgow, starting in November 2018. It was logged in January 2019 to provide a record of subsurface temperature to 197 m depth, in this urban area with a long history of coal mining and industrial development. This borehole temperature record is significantly perturbed away from its natural state, in part because of the ‘permeabilizing’ effect of past nearby coal mining and in part due to surface warming as a result of the combination of anthropogenic climate change and creation of a subsurface urban heat island by local urban development. Our numerical modelling indicates the total surface warming effect as 2.7°C, partitioned as 2.0°C of global warming since the Industrial Revolution and 0.7°C of local UHI development. We cannot resolve the precise combination of local factors that influence the surface warming because uncertainty in the subsurface thermal properties trades against uncertainty in the history of surface warming. However, the background upward heat flow through the shallow subsurface is estimated as only c. 28–33 mW m−2, depending on choice of other model parameters, well below the c. 80 mW m−2 expected in the Glasgow area. We infer that the ‘missing’ geothermal heat flux is entrained by horizontal flow at depth beyond the reach of the shallow GGC-01 borehole. Although the shallow subsurface in the study area is warmer than it would have been before the Industrial Revolution, at greater depths – between c. 90 and >300 m – it is colder, due to the effect of reduced background heat flow. In future the GGERFS project might utilize water from depths of c. 90 m, but the temperature of the groundwater at these depths is maintained largely by the past effect of surface warming, due to climate change and urban development; it is thus a resource that might be ‘mined’ but not sustainably replenished and, being the result of surface warming rather than upward heat flow, arguably should not count as ‘geothermal’ heat in the first place. Our analysis thus indicates that the GGERFS site is a poor choice as a test site for mine-water geothermal heat.Supplementary material: A summary history of coal mining in the study area is available at: https://doi.org/10.6084/m9.figshare.c.4911495.v2

scholarly journals Compact Integrated Bluetooth UWB Antenna with Quadruple Bandnotched Characteristics

2015 ◽  
Vol 5 (6) ◽  
pp. 1433
Author(s):  
Rekha P Labade ◽  
Shankar B Deosarkar ◽  
Narayan Pisharoty
Keyword(s):  
Time Domain ◽  
Group Delay ◽  
Directional Pattern ◽  
Good Time ◽  
Uwb Antenna ◽  
Half Wavelength ◽  
Quarter Wavelength ◽  
Uwb Applications

In this paper,a compact printed dualband antenna for Bluetooth and UWB applications with WiMax(3.3-3.7 GHz), C-band satellite downlink(3.7-4.2GHz), WLAN(5.15-5.825GHz) and DSRC(5.5-5.925GHz) bandnotched characteristics is proposed and investigated. By etching two half-wavelength L-shaped slots in the radiating patch and an inverted U-shaped slot in the microstrip feedline quadruple bandnotched characteristics is obtained. Further, by embedding quarter wavelength parasitic strip at two edges of U-shaped radiating patch dualband characteristics with desired bandwidth is obtained. the proposed antenna is designed and fabricated on a FR4 substrate of dimensions 24mm X 35mm that operates over a 2.4-11GHz with S11<-10dB except over notch bands of 3.3-3.7GHz, 3.7-4.2GHz,5.15-5.625GHz and 5.625-6GHz. Directional pattern in E-plane and nearly omnidirectional pattern in H-plane are observed over a UWB band except at desired bandnotched freqencies. Less variation in group delay and pulse deformation shows good time domain characteristics. In addition, the structure exhibits stable gain over the desired band.

Distributed acoustic sensing for shallow seismic investigations and void detection

Geophysics ◽  
2021 ◽  
pp. 1-69
Author(s):  
Yarin Abukrat ◽  
Moshe Reshef
Keyword(s):  
Vertical Component ◽  
Test Site ◽  
Wave Mode ◽  
Invasive Technique ◽  
S Wave ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Shallow Subsurface ◽  
Diffraction Imaging ◽  
Distributed Acoustic Sensing

During the last decade, fiber-optic-based distributed acoustic sensing (DAS) has emerged as an affordable, easy-to-deploy, reliable, and non-invasive technique for high-resolution seismic sensing. We show that fiber deployments dedicated to near-surface seismic applications, commonly employed for the detection and localization of voids, can be used effectively with conventional processing techniques. We tested a variety of small-size sources in different geological environments. These sources, operated on and below the surface, were recorded by horizontal and vertical DAS arrays. Results and comparisons to data acquired by vertical-component geophones demonstrate that DAS may be sufficient for acquiring near-surface seismic data. Furthermore, we tried to address the issue of directional sensing by DAS arrays and use it to solve the problem of wave-mode separation. Records acquired by a unique acquisition setup suggest that one can use the nature of DAS systems as uniaxial strainmeters to record separated wave modes. Lastly, we applied two seismic methods on DAS data acquired at a test site: multi-channel analysis of surface waves (MASW) and shallow diffraction imaging. These methods allowed us to determine the feasibility of using DAS systems for imaging shallow subsurface voids. MASW was used to uncover anomalies in S-wave velocity, whereas shallow diffraction imaging was applied to identify the location of the void. Results obtained illustrate that by using these methods we are able to accurately detect the true location of the void.

Constructing a geophysical test site for a coastal community's research and education activities

2021 ◽  
Vol 40 (3) ◽  
pp. 208-215
Author(s):  
Mohamed Ahmed ◽  
Ryan Turner ◽  
Michael Haley ◽  
Samantha Shyrigh ◽  
Dionel Colmenero ◽  
...  
Keyword(s):  
Research Training ◽  
Real Life ◽  
Test Site ◽  
Site Location ◽  
Geophysical Research ◽  
Shallow Subsurface ◽  
Steel Pipes ◽  
Corpus Christi ◽  
Steel Drums ◽  
Research And Education

A geophysical test site (GTS) contains subsurface targets of known materials, orientations, and depths. GTSs offer unique opportunities for geophysical research, training, and educational activities. They provide platforms to investigate the penetration and resolution of different geophysical techniques for characterizing the shallow subsurface. GTS-based field exercises represent an interesting, motivating, rewarding, and enjoyable experience for students and instructors. We have constructed a GTS at Texas A&M University-Corpus Christi that contains several objects (e.g., steel drums, plastic drums, plastic buckets, steel pipes, and well covers) buried at depths ranging from 0.5 to 3 m to simulate real-life situations. In this article, we provide a thorough description of the site location, subsurface geology, surface topography, and construction methodology, as well as the types, locations, orientations, and depths of the subsurface targets. Research and education significance and implications of the GTS are also described. This article could serve as a reference for the construction of new GTSs worldwide.

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