The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Don W. Steeples - One of the best experts on this subject based on the ideXlab platform.
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Pitfalls In Shallow Seismic Reflection
7th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems, 2012Co-Authors: Don W. Steeples, Richard D. MillerAbstract:Substantial progress has occurred during the past 15 years in development of shallow CDP Seismic-Reflection techniques, but there are occasional interpretation problems with the resulting data. We discuss examples of the pitfalls of the method, along with some procedures to help avoid them. Problems that often occur include spatial aliasing of ground roll, interpreting processed ground-coupled air waves as true Seismic waves, misinterpreting refractions as Reflections on stacked CDP sections, and not recognizing processing artifacts. Aliasing occurs when data are not sampled often enough in time and/or space. Decreasing the geophone interval by a substantial amount (such as a factor of two) will improve coherency of a true reflector, but will destroy coherency of spatially aliased ground roll. It is often difficult to separate shallow Reflections from shallow refractions during processing. Reflected energy from shallow depths tends to have frequency content close to that of the direct wave and/or early refracted arrivals on field seismograms. Refractions on a stacked section tend to be a bit lower in frequency because the NM0 correction in a CDP stack assumes hyperbolic moveout, while refractions arrive as a linear time-distance function. Hence, they don’t stack as coherently as Reflections, which decreases their frequency. Processing artifacts from inadequate velocity analysis and inaccurate static corrections are at least as troublesome on shallow Reflection sections as they are on classical Reflection surveys from petroleum exploration. It has been our experience that occasional field records will display unusually good Reflections. These field seismograms can be used to correlate to the processed Seismic sections. Unequivocally separating shallow Reflections from shallow refractions is clearly one of the major limitations of the shallow-Seismic Reflection method at present.
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Shallow Seismic Reflection does not always work
Seg Technical Program Expanded Abstracts, 2012Co-Authors: Richard D. Miller, Don W. SteeplesAbstract:Summary Shallow Seismic Reflection has seen widespread use in a variety of environmental, groundwater, and engineering applications over the last 15 years. Seismic Reflection, like any other geophysical technique, has reasonably well defined limitations. Besides the well-published resolution limitation, the effectiveness of the technique is strongly dependent, and in many cases controlled, by near-surface conditions. Moisture content, sorting, grain size, organic matter, and consolidation are just a few of the key properties of the near-surface that can dramatically affect the quality of Seismic Reflection data. In some difficult data areas thoughtful parameter design, high-quality equipment (large dynamic range and small electronic noise), and careful processing can overcome adverse near-surface c onditions. Tendencies to suggest that data processing is the key to bringing out Reflections on CMP stacks that are not identifiable on shot or CMP gathers leads to overselling the technique and inevitable skepticism by clients and potential clients as to the reliability of shallow Seismic Reflection. As difficult as it may be for shallow Seismic Reflection practitioners to admit, shallow Seismic Reflection simply will not work in some settings and for some targets.
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Migration of shallow Seismic Reflection data
Geophysics, 2012Co-Authors: Ross A. Black, Don W. Steeples, Richard D. MillerAbstract:We present an analysis of migration effects on Seismic Reflection images of very shallow targets such as those that are common objectives of engineering, groundwater, and environmental investigations. We use an example of Seismic Reflection data from depths of 5 to 15 m that show negligible effect from migration, despite the apparent steep dip on the Seismic section. Our analysis of the question of when to migrate shallow Reflection data indicates it is critical to take into account the highly variable near‐surface velocities and the vertical exaggeration on the Seismic section. A simple set of calculations is developed as well as a flow chart based on the “migrator’s equation” that can predict whether migration of an arbitrary shallow Seismic section is advisable. Because shallow Reflection data are often processed on personal computers, unnecessary migration of a large data set can be prohibitively time‐consuming and wasteful.
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3-D Design For a Near-surface Seismic Reflection Investigation
Seg Technical Program Expanded Abstracts, 2012Co-Authors: Brian E. Miller, George P. Tsoflias, Don W. SteeplesAbstract:3-D Seismic Reflection methods have been established as the predominant Seismic method for exploration scale purposes. While this is true for exploration scale surveys the same is not yet true for near-surface Seismic Reflection investigations. While the benefits of employing 3-D methods have been documented they are still yet to be fully adopted by the near-surface community. There are a number of reasons for this; primary among them is the difficulty in planting large numbers of geophones. Adding to this is the cost involved with the increased amount of equipment required. Additional concerns arise because planning a 3-D survey requires more consideration that a 2D survey. While both must address the same basic questions such as depth to target and resolution, planning a 3-D survey must take additional requirements, such as azimuth, into consideration as part of the design.
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Shallow subsurface applications of high‐resolution Seismic Reflection
Journal of the Acoustical Society of America, 2002Co-Authors: Don W. SteeplesAbstract:Shallow Seismic Reflection surveys have been applied to a wide variety of problems. For example, in many geologic settings, variations and discontinuities on the surface of bedrock can influence the transport and eventual fate of contaminants introduced at or near the ground surface. Using Seismic methods to determine the nature and location of anomalous bedrock can be an essential component of hydrologic characterization. Shallow Seismic surveys can also be used to detect earthquake faults and to image underground voids. During the early 1980s, the advent of digital engineering seismographs designed for shallow, high‐resolution surveying spurred significant improvements in engineering and environmental Reflection seismology. Commonly, shallow Seismic Reflection methods are used in conjunction with other geophysical and geological methods, supported by a well‐planned drilling‐verification effort. To the extent that Seismic Reflection, refraction, and surface‐wave methods can constrain shallow stratigraphy...
Richard D. Miller - One of the best experts on this subject based on the ideXlab platform.
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Seismic Reflection: Upstream, Downstream, And On Earthen Dams And Dikes
20th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems, 2012Co-Authors: Richard D. Miller, Richard D. Markiewicz, Lisa Block, Steve Hartung, William E. Hancock, Julian IvanovAbstract:High-resolution Seismic Reflection has been used successfully to characterize material and investigate a variety of problems associated with earthen dams and abutments. Limitations and challenges of Seismic Reflection when interrogating these structures and lithologies are nontrivial and require very critical thinking. Seismic Reflection has proved an effective tool for mapping confining units for integration into the cutoff wall at the Keechelus Dam in Cle Elum, Washington; mapping lithologies and bedrock structures for earthquake retrofitting at Bend, Oregon; delineating karst in bedrock beneath the dam core responsible for subsidence on the upstream side of a major flood control structure at Clearwater Dam, Missouri; and detecting high permeability zones within a glacial outwash embankment of a water retention dam near Enumclaw, Washington. Extreme geometries and material variability associated with any man-made structure are the most formidable challenge to Seismically imaging. Inconsistent source wavelets, out-of-the-plane energy, extreme statics (topography and velocity based), and source noise (disproportionately high percentage of surface waves) are all problems that are not unique to earthen dams, dikes, and levees, but they are certainly more prevalent with those types of structures. Success of the technique in these settings is source characteristics and spatial oversampling.
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Pitfalls In Shallow Seismic Reflection
7th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems, 2012Co-Authors: Don W. Steeples, Richard D. MillerAbstract:Substantial progress has occurred during the past 15 years in development of shallow CDP Seismic-Reflection techniques, but there are occasional interpretation problems with the resulting data. We discuss examples of the pitfalls of the method, along with some procedures to help avoid them. Problems that often occur include spatial aliasing of ground roll, interpreting processed ground-coupled air waves as true Seismic waves, misinterpreting refractions as Reflections on stacked CDP sections, and not recognizing processing artifacts. Aliasing occurs when data are not sampled often enough in time and/or space. Decreasing the geophone interval by a substantial amount (such as a factor of two) will improve coherency of a true reflector, but will destroy coherency of spatially aliased ground roll. It is often difficult to separate shallow Reflections from shallow refractions during processing. Reflected energy from shallow depths tends to have frequency content close to that of the direct wave and/or early refracted arrivals on field seismograms. Refractions on a stacked section tend to be a bit lower in frequency because the NM0 correction in a CDP stack assumes hyperbolic moveout, while refractions arrive as a linear time-distance function. Hence, they don’t stack as coherently as Reflections, which decreases their frequency. Processing artifacts from inadequate velocity analysis and inaccurate static corrections are at least as troublesome on shallow Reflection sections as they are on classical Reflection surveys from petroleum exploration. It has been our experience that occasional field records will display unusually good Reflections. These field seismograms can be used to correlate to the processed Seismic sections. Unequivocally separating shallow Reflections from shallow refractions is clearly one of the major limitations of the shallow-Seismic Reflection method at present.
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Shallow Seismic Reflection does not always work
Seg Technical Program Expanded Abstracts, 2012Co-Authors: Richard D. Miller, Don W. SteeplesAbstract:Summary Shallow Seismic Reflection has seen widespread use in a variety of environmental, groundwater, and engineering applications over the last 15 years. Seismic Reflection, like any other geophysical technique, has reasonably well defined limitations. Besides the well-published resolution limitation, the effectiveness of the technique is strongly dependent, and in many cases controlled, by near-surface conditions. Moisture content, sorting, grain size, organic matter, and consolidation are just a few of the key properties of the near-surface that can dramatically affect the quality of Seismic Reflection data. In some difficult data areas thoughtful parameter design, high-quality equipment (large dynamic range and small electronic noise), and careful processing can overcome adverse near-surface c onditions. Tendencies to suggest that data processing is the key to bringing out Reflections on CMP stacks that are not identifiable on shot or CMP gathers leads to overselling the technique and inevitable skepticism by clients and potential clients as to the reliability of shallow Seismic Reflection. As difficult as it may be for shallow Seismic Reflection practitioners to admit, shallow Seismic Reflection simply will not work in some settings and for some targets.
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Migration of shallow Seismic Reflection data
Geophysics, 2012Co-Authors: Ross A. Black, Don W. Steeples, Richard D. MillerAbstract:We present an analysis of migration effects on Seismic Reflection images of very shallow targets such as those that are common objectives of engineering, groundwater, and environmental investigations. We use an example of Seismic Reflection data from depths of 5 to 15 m that show negligible effect from migration, despite the apparent steep dip on the Seismic section. Our analysis of the question of when to migrate shallow Reflection data indicates it is critical to take into account the highly variable near‐surface velocities and the vertical exaggeration on the Seismic section. A simple set of calculations is developed as well as a flow chart based on the “migrator’s equation” that can predict whether migration of an arbitrary shallow Seismic section is advisable. Because shallow Reflection data are often processed on personal computers, unnecessary migration of a large data set can be prohibitively time‐consuming and wasteful.
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High-resolution Seismic Reflection to image hydrogeologic sequences
Seg Technical Program Expanded Abstracts, 2012Co-Authors: Richard D. MillerAbstract:Introduction High-resolution Seismic Reflection has been successfully used to delineate preferential pathways within groundwater systems that represent corridors for contaminant movement in a wide variety of challenging hydrologic settings, many in settings where other methods and/or monitor wells have not been enlightening. For more than four decades, Seismic Reflection has found utility addressing near-surface groundwater problems where lateral variability of confining layers have inhibited even the most sophisticated flow models developed from monitor wells (Shepers, 1975). Optimizing acquisition and processing parameters while limiting interprettations to only what can be validated on shot records and consistent with wave propagation and Reflection theory is essential for making meaningful and reliable contributions to a groundwater flow model and associated monitoring and remediation programs (Steeples and Miller, 1990). Years of application of the method in a wide range of settings and with a diverse set of imaging objectives has resulted in an excellent collection of case studies that provides guidance for current and future applications and developments as well as evaluations of method feasibility. The Seismic Reflection method has been used to establish lateral continuity in confining units with thick dry sandy overburdens as well as fine-grained unconsolidated and saturated near-surface settings. Mapping bedrock is an important application where percolation rates in the vadose zone are high and bedrock units are impermeable. Seismic Reflection is a viable tool for studying sitewide variability in unconsolidated alluvial sediments where complex vertical migration paths can allow contaminants to easily move between local “confining” layers, leaving zones directly beneath a source contaminant free, while deeper layers, seemingly protected by several aquicludes, are rich in contaminant. The complexity of many depositional settings results in rapid vertical changes in material properties and therefore a need for high-resolution imaging that does not require a priori information or assumptions about the sequential nature of the vertical property changes. Even with Seismic Reflection’s many positive and sometimes amazing attributes and capabilities, it is imperative that an awareness of the method’s limitations and true potential in real-world settings be maintained. Near-surface Seismic methods do not lend themselves to distinguishing different types of liquids within a groundwater system. For example, distinguishing DNAPLs or LNAPLs from within a saturated interval is beyond the resolution of the Seismic tool in real-world settings. However, interrogation of the subsurface in search of lithologies or structures that might represent traps for contaminants has proven very effective. In fact, based on the properties of liquids in the subsurface, it is many times possible to infer traps and likely areas of high concentrations based on mapped reflector structures in conjunction with well control.
Andre J M Pugin - One of the best experts on this subject based on the ideXlab platform.
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near surface s wave Seismic Reflection profiling new approaches and insights
First Break, 2013Co-Authors: Andre J M Pugin, S E Pullan, K D Brewer, T Cartwright, D Perret, Heather Crow, J A HunterAbstract:Multi-component high resolution Seismic Reflection profiling has been extensively tested over a wide variety of ground surfaces across the southern provinces of Canada, showing new potential for applications of the method in groundwater and natural hazards research. The near-surface shear-wave Reflection method using vibratory sources and short spacing land streamers equipped with three-component receivers is an excellent tool for accurately characterizing shear-wave velocities and recording optimal, non-aliased shear-wave data in the most polarized direction. A small portable multi-component vibrator developed at the Geological Survey of Canada (GSC) named ‘Microvibe’ provides higher frequency S-wave and P-wave signals than can be acquired with a Minivib I. In this paper we show that the shear-wave polarization can vary with depth and it may be necessary to combine multiple components together to achieve an optimized stacked section. Significant velocity anisotropies of up to 15% have been observed between the horizontal and vertical directions when using this multicomponent Microvibe source. We make key recommendations based on time and space sampling recording windows for successful near surface PP-wave, PS-wave and SS-wave Seismic Reflection surveys. Using field examples and velocity measurements, we show the complexity of velocities in non-homogeneous media in the near surface.
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multicomponent high resolution Seismic Reflection profiling
Geophysics, 2009Co-Authors: Andre J M Pugin, S E Pullan, James A HunterAbstract:Multicomponent Seismic Reflection methods are a new tool for oil and gas exploration and reservoir monitoring (Miles 1988), but such technologies have not yet been extensively exploited for near-surface exploration related to hydrogeological and/or geotechnical investigations. With the advantage of relatively inexpensive recording systems for near-surface applications, we show that the use of multicomponent high-resolution Seismic Reflection methods has great potential as a new means of observing and characterizing the physical parameters of the shallow subsurface, and in particular of groundwater reservoirs.
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hydrogeological prospecting using p and s wave landstreamer Seismic Reflection methods
Near Surface Geophysics, 2009Co-Authors: Andre J M Pugin, S E Pullan, James A Hunter, Greg A OldenborgerAbstract:We present two case histories from different areas and geological settings in Canada where we have used a vibrating Seismic source coupled to a landstreamer receiver array in hydrogeological investigations related to aquifers in glacial sediments. In Manitoba, our P-wave Seismic Reflection profiles are used to provide an assessment of the subsurface architecture of buried valleys, estimate the thickness and properties of both the channel fill and the overlying sediments to depths of ~100 m and locate optimum sites for groundwater well placements. In eastern Ontario, we collected P- and S-wave Seismic Reflection as well as electrical resistivity data to investigate buried esker aquifers. The geophysical data provide detailed high-resolution information (to ~30 m depth) on the structure of the esker core and its overlying sand cover and on the thickness and variability of the overlying fine-grained aquitard. The data presented in this paper demonstrate that shallow Seismic Reflection methods are very effective tools to explore, assess and evaluate groundwater reservoirs and resources. The recent advent of landstreamer receiver arrays, especially when coupled to a vibratory Seismic source, makes these methods significantly more cost-effective and efficient. We now routinely collect ~1000 records/day, or 1.5-6 line-km/day, using our Minivib/landstreamer data acquisition system. With this type of efficient data collection, it is anticipated that the use of shallow Seismic Reflection methods in hydrogeological prospecting will increase as groundwater and its protection become more valued by society.
S E Pullan - One of the best experts on this subject based on the ideXlab platform.
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near surface s wave Seismic Reflection profiling new approaches and insights
First Break, 2013Co-Authors: Andre J M Pugin, S E Pullan, K D Brewer, T Cartwright, D Perret, Heather Crow, J A HunterAbstract:Multi-component high resolution Seismic Reflection profiling has been extensively tested over a wide variety of ground surfaces across the southern provinces of Canada, showing new potential for applications of the method in groundwater and natural hazards research. The near-surface shear-wave Reflection method using vibratory sources and short spacing land streamers equipped with three-component receivers is an excellent tool for accurately characterizing shear-wave velocities and recording optimal, non-aliased shear-wave data in the most polarized direction. A small portable multi-component vibrator developed at the Geological Survey of Canada (GSC) named ‘Microvibe’ provides higher frequency S-wave and P-wave signals than can be acquired with a Minivib I. In this paper we show that the shear-wave polarization can vary with depth and it may be necessary to combine multiple components together to achieve an optimized stacked section. Significant velocity anisotropies of up to 15% have been observed between the horizontal and vertical directions when using this multicomponent Microvibe source. We make key recommendations based on time and space sampling recording windows for successful near surface PP-wave, PS-wave and SS-wave Seismic Reflection surveys. Using field examples and velocity measurements, we show the complexity of velocities in non-homogeneous media in the near surface.
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multicomponent high resolution Seismic Reflection profiling
Geophysics, 2009Co-Authors: Andre J M Pugin, S E Pullan, James A HunterAbstract:Multicomponent Seismic Reflection methods are a new tool for oil and gas exploration and reservoir monitoring (Miles 1988), but such technologies have not yet been extensively exploited for near-surface exploration related to hydrogeological and/or geotechnical investigations. With the advantage of relatively inexpensive recording systems for near-surface applications, we show that the use of multicomponent high-resolution Seismic Reflection methods has great potential as a new means of observing and characterizing the physical parameters of the shallow subsurface, and in particular of groundwater reservoirs.
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hydrogeological prospecting using p and s wave landstreamer Seismic Reflection methods
Near Surface Geophysics, 2009Co-Authors: Andre J M Pugin, S E Pullan, James A Hunter, Greg A OldenborgerAbstract:We present two case histories from different areas and geological settings in Canada where we have used a vibrating Seismic source coupled to a landstreamer receiver array in hydrogeological investigations related to aquifers in glacial sediments. In Manitoba, our P-wave Seismic Reflection profiles are used to provide an assessment of the subsurface architecture of buried valleys, estimate the thickness and properties of both the channel fill and the overlying sediments to depths of ~100 m and locate optimum sites for groundwater well placements. In eastern Ontario, we collected P- and S-wave Seismic Reflection as well as electrical resistivity data to investigate buried esker aquifers. The geophysical data provide detailed high-resolution information (to ~30 m depth) on the structure of the esker core and its overlying sand cover and on the thickness and variability of the overlying fine-grained aquitard. The data presented in this paper demonstrate that shallow Seismic Reflection methods are very effective tools to explore, assess and evaluate groundwater reservoirs and resources. The recent advent of landstreamer receiver arrays, especially when coupled to a vibratory Seismic source, makes these methods significantly more cost-effective and efficient. We now routinely collect ~1000 records/day, or 1.5-6 line-km/day, using our Minivib/landstreamer data acquisition system. With this type of efficient data collection, it is anticipated that the use of shallow Seismic Reflection methods in hydrogeological prospecting will increase as groundwater and its protection become more valued by society.
J A Hunter - One of the best experts on this subject based on the ideXlab platform.
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near surface s wave Seismic Reflection profiling new approaches and insights
First Break, 2013Co-Authors: Andre J M Pugin, S E Pullan, K D Brewer, T Cartwright, D Perret, Heather Crow, J A HunterAbstract:Multi-component high resolution Seismic Reflection profiling has been extensively tested over a wide variety of ground surfaces across the southern provinces of Canada, showing new potential for applications of the method in groundwater and natural hazards research. The near-surface shear-wave Reflection method using vibratory sources and short spacing land streamers equipped with three-component receivers is an excellent tool for accurately characterizing shear-wave velocities and recording optimal, non-aliased shear-wave data in the most polarized direction. A small portable multi-component vibrator developed at the Geological Survey of Canada (GSC) named ‘Microvibe’ provides higher frequency S-wave and P-wave signals than can be acquired with a Minivib I. In this paper we show that the shear-wave polarization can vary with depth and it may be necessary to combine multiple components together to achieve an optimized stacked section. Significant velocity anisotropies of up to 15% have been observed between the horizontal and vertical directions when using this multicomponent Microvibe source. We make key recommendations based on time and space sampling recording windows for successful near surface PP-wave, PS-wave and SS-wave Seismic Reflection surveys. Using field examples and velocity measurements, we show the complexity of velocities in non-homogeneous media in the near surface.
