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22nd EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
- Conference date: 29 Mar 2009 - 02 Apr 2009
- Location: Forth Worth, Texas, USA
- Published: 29 March 2009
61 - 80 of 124 results
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Seismic Recordings of an Anthropogenic Sinkhole Collapse
More LessOn July 16, 2008, a sinkhole several tens of meters in diameter formed abruptly at the site of a brine well in Eddy Co., NM. The well operator had been injecting fresh water into salt beds of the Permian Salado Formation and pumping out the resulting brine for use as oil field drilling fluid. Borehole problems had prevented the operator from conducting required downhole sonar surveys to assess the dimensions of the resulting subsurface void and the collapse was unanticipated.
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Soil Magnetism Research: State of the Art and Future Directions - Keynote Session
Authors J. Hannam, R. Van Dam and R. HarmonMagnetic properties of soils have been highlighted as a primary detrimental environmental effect
on the performance of geophysical systems for detection of unexploded ordnance (UXO) and mine
targets. A recent workshop at Cranfield University, U.K., aimed to identify knowledge gaps related to
soil magnetism. Eight invited speakers from multidisciplinary areas provided briefings on state-of-theart
research linked to soil magnetism and geophysical sensing.
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Audio frequency magnetic induction in soils
By G. WestSoils often possess a measurable magnetic susceptibility, due to the presence of ferromagnetic minerals such as magnetite and maghemite. Sometimes, this susceptibility is appreciably dispersive (frequency and delay time-dependent) because the grains are small enough to approach the thermal agitation limit of superparamagnetism. Dispersion can be important in applied geophysics and related fields like archeology and demining.
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Determination of the Magnetic Viscosity for Cold-Rolled Carbon-Steel 55-Gallon Drums in Earth's Magnetic Field
Authors C. Freed, E. Doheny and T. BechtelContainers that are used to transport hazardous waste are usually drums constructed of cold-rolled carbon steel with a volume of 55 gallons. During the drum manufacturing process, the annealing, extruding, and cold rolling of the steel into sheets exerts stresses on the steel’s microstructure which destroy pinning sites between magnetic domains, allowing these domains to rotate and elongate with less required energy, resulting in magnetically softer steel.
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Characteristics of Lightning-induced Magnetic Anomalies in Low-altitude Aeromagnetic Data
Authors L. Beard, J. Norton and J. SheehanA low altitude helicopter magnetic survey for unexploded ordnance in New Mexico
revealed several magnetic anomalies that were likely induced by lightning strikes. Lightningstrike
magnetic anomalies are not necessarily rare, but are often widely spaced. Detailed
examples are not often reported because ground geophysical surveys may not cover enough area
to detect one, and traditional airborne surveys, which do cover large areas, are carried out at an
altitude and line spacing which does not appropriately outline the shape of the lightning strike
anomaly.
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Application of Magnetic Susceptibility for Wetlands Delineation
More LessWetlands are a natural resource that are protected under federal regulations, therefore the
delineation of wetlands is necessary to ensure their protection. A study using magnetic susceptibility
was undertaken in central Mississippi to identify the transitional zone between non-hydric (uplands) and
hydric (wetlands) soils. The soils were clayey with a minor percentage of sand. A survey line that
traversed an upland, transitional zone, and wetland on each end of a transect was revisited four times
during a single year.
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Shot Gathers We Have Known
Authors R. Miller, J. Xia, J. Ivanov and S. WaltersUnequivocal identification of reflections on shot gathers is not only necessary, it is mandatory for meaningful interpretations of shallow, CMP stacked seismic sections. With shallow seismic shot gathers from hundreds of sites, we have tackled the entire range of near-surface settings and associated obstacles to high quality reflection sections. Imaging objectives have ranged from hydrogeologic charac-terization to fault mapping to stratigraphic variations.
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Shallow Shear-Wave Seismic Characterization of a Pleistocene Gravel Deposit, Yazoo County, Mississippi
Authors J. Harris, D. Smolkin, D. Butler and S. GalickiThe combined production of sand and gravel is the most economically important industrial
mineral resource in Mississippi. In central Mississippi, including the Jackson metropolitan area, most
gravel used in construction projects comes from pre-loess (Pleistocene) terrace deposits of the ancestral
Mississippi River.
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Mapping Buried Valley Aquifers in SW Manitoba using a Vibrating Source/Landstreamer Seismic Reflection System
More LessIn southwest Manitoba, Canada, sand and gravel aquifers within buried valleys of Pleistocene and/or Tertiary age eroded into underlying Cretaceous bedrock have been developed for municipal, pipeline and farm water supplies. These valleys have little or no surface expression and the sedimentary architecture is poorly known; the extent of the valleys and their aquifers has been only partially delineated by boreholes.
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Angle-dependent Tomostatics
Authors L. Mayer, R. Miller, J. Ivanov, T. Weis and B. AndersonStatics are a dynamic problem that affects most seismic surveys. The key to addressing the statics problem is an accurate estimation of near-surface velocity variability. Reflection velocity analysis is critical to meaningful CMP stacks, however a reliable velocity function depends on reflections with the trace-to-trace static variability associated with an irregular near-surface velocity. Using conventional correlation approaches the problem then becomes cyclic because the relationship between statics estimations and corrections are intertwined with reflection velocity analysis.
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Estimation of Absorbing Boundary Parameters for Near Surface Seismic Modeling
More LessArtificial boundaries are necessary in seismic numerical modeling to constrain the computational limits. Special treatment is necessary to reduce spurious reflections from these artificial boundaries. For near-surface seismic modeling, boundary processing is particularly important due to the presence of surface waves. The Perfectly Matched Layer (PML) method is an efficient way of attenuating boundary reflections of body waves and surface waves.
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Vehicle Traffic as a Source for Near-Surface Passive Seismic Imaging
Authors H.A. Kuzma, J.L. Fernández Martínez, Z. Yang, D. Clark, Z. Mingyue, M.-D. Mangriotis and J.W. RectorIn this paper, we present preliminary results from a field experiment in which we explored the
use of cars and traffic as a source for passive seismic imaging. We set out a line of geophones at a 45
degree angle between two intersecting roads at the University of California, Richmond Field Station.
We collected data sets including background noise, an idling car at the intersection of the roads, one car
driving on one road and two cars driving on both roads.
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Effect of Array Shape on the Spatial Auto-correlation Analysis of Microtremor Array Measurements
By K. HayashiWe have applied the micro-tremor array measurements (MAM) to shallow S-wave velocity
investigations and evaluated the applicability of the method. Unlike the active surface wave methods,
the MAM does not need any sources and needs two-dimensional arrays, such as triangles, circles or
crosses. Because the sources of the microtremor are distributed randomly in space, the microtremor does
not have any specific propagation directions.
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Roadside MASW Surveys Using a Portable Road Bump : A Case-Study in Managua, Nicaragua
Authors E. Obando, C. Park, N. Ryden and P. UlriksenThe Passive Roadside MASW has become a feasible alternative for constructing relatively deep
shear wave velocity profiles. We present a case study that uses a portable rubber cable protector as a
source, producing very low-frequency impulses as it is struck by vehicles. A linear receiver array was
laid out perpendicular to the road with the first geophone 100 meters away from the road.
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Automatic Localization of Acoustic Sensors
Authors G. Bernasconi and D. RovettaMany geophysical applications require the acquisition of multichannel data with sensor networks
(e.g. seismic geophones) and/or the sequential acquisition in stations along a defined trajectory (e.g.
GPR profile). In all these situations the accuracy of the processed data is linked to the proper spatial
sampling and to the knowledge of the location of the individual station points.
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Fiber Optic Seismic Excitation Modeling
Authors S. McComas, M. McKenna, J. McKenna and K. KoppenhoeferAn experimental fiber optic seismic sensor and conventional point seismic sensors were
deployed to monitor human generated signals in the US Southwest. Data from the two techniques were
compared and the frequency domain results correlated well. Finite element modeling was performed to
verify the results of the data collection. A high-performance computing code, PSTOP3D, was compared
to desktop modeling performed using COMSOL Multiphysics using real-world parameters collected
during the experiment
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Bridge Deck Assessment Using Ground Penetrating Radar (GPR)
Authors A. Wamweya, E. Torgashov and N. AndersonGPR data were acquired across two bridge decks: one with a hot bituminous wearing surface and a second with a bare concrete slab. The acquired GPR data were interpreted, and two plan view maps were generated: one depicts the magnitude of the reflections from the uppermost mat of rebar; the second depicts the arrival time of these reflections.
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Infrasound Assessment of a Railroad Bridge
Authors M. McKenna, S. McComas, A. Lester and P. MlakarInfrasound is acoustic energy whose frequency is below that of human perception. Large
infrastructure, such as bridges, emits such signals at their natural or driven frequencies of vibration.
These frequencies can provide an indication of the structural condition.
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A Challenging GPR Investigation to Assess the State of Damage of a Water Tunnel
More LessThe GPR method was used to assess the conditions of a water tunnel built to force a river to
underpass the road running along the Valganna valley, 60km north of Milan (Italy). The tunnel is
concrete lined and has a semicircular section with a diameter that varies between 3 and 4m. The most
damaged section of the tunnel runs parallel to the valley for about 300m before intersecting the road
where the valley makes a pronounced left turn.
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Practical Applications using CSL and GDL in Combination for Drilled Shaft Testing
Authors M. Rucker, M. Manthey, S. Surlaker and J. PhillipsCrosshole Sonic Logging (CSL) and Gamma Density Logging (GDL) provide complementary
capabilities and limitations when used for non-destructive integrity testing of drilled shafts used as
foundation elements in bridges, buildings and other structures.
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