Estimation of near‐surface elastic parameters using multicomponent seismic data

Geophysics ◽  
1993 ◽  
Vol 58 (7) ◽  
pp. 1017-1029 ◽  
Author(s):  
E. Z. Ata ◽  
D. Corrigan ◽  
G. A. McMechan ◽  
J. E. Gaiser
Keyword(s):  
Field Data ◽  
Signal To Noise Ratio ◽  
Surface Effects ◽  
Test Site ◽  
Compressional Wave ◽  
Elastic Parameters ◽  
Surface Source ◽  
Near Surface ◽  
Multicomponent Seismic ◽  
Single Fold

In multicomponent seismic reflection surveys, surface and near‐surface effects can severely deteriorate the quality of reflection data. Such effects are more pronounced on shear‐wave than on compressional‐wave profiles. Amplitude anomalies, statics, and strong coherent source‐generated noise (i.e., surface waves) are often associated with inhomogeneous, poorly compacted near‐surface sediments of the weathering layer. The magnitude of such effects increases when sources and receivers are deployed at or near the surface in proximity to such inhomogeneities. Near‐surface effects can be investigated with respect to their depth of occurrence by burying seismic sources and/or receivers at various depths below the inhomogeneous weathering layer. In this context, an experiment was conducted to collect multicomponent seismic field data on a borehole‐controlled test site in east Texas. Data were recorded on three‐component surface and buried receivers using a full‐vector wavefield surface source. Although the geology appears simple, results of modeling one or two components of the field data with synthetics yields nonunique estimates of elastic parameters. Effects of anisotropy and heterogeneities are better identified and estimated with full‐wavefield surface and buried receiver observations. Single fold data from buried receivers yield reflection events with higher signal‐to‐noise ratio than 30‐fold CDP surface data previously acquired in the same area.

Northwestern Williston Basin case histories with 3-D seismic data

Geophysics ◽  
1991 ◽  
Vol 56 (11) ◽  
pp. 1849-1874
Author(s):  
D. L. Connelly ◽  
B. J. Ferris ◽  
L. D. Trembly
Keyword(s):  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Cost Effective ◽  
Field Studies ◽  
Careful Analysis ◽  
Williston Basin ◽  
Event Correlation ◽  
Near Surface ◽  
Single Fold ◽  
Exploration Area

Two Northwestern Williston Basin field studies illustrate the cost‐effective geological and three‐dimensional seismic methods used to explore for structurally controlled oil reservoirs in the Tule Creek area of northeast Montana. These examples present the geologic and seismic characteristics of a Mississippian Charles C zone pool at Northwest Poplar field and a Devonian Nisku accumulation at Long Creek West field. A classic, upward‐shoaling, nearshore marine carbonate sequence characterizes the reservoir and associated strata in both fields. The Charles C zone pool of Northwest Poplar field is a subtle, tectonically‐controlled accumulation which remained undiscovered and downdip from the large, nearby, well‐known East Poplar field until 1983. Long Creek West field exhibits the subtle character of small closed structures produced by multistage evaporite solution. Three‐dimensional (3-D) seismic techniques best detect such fields of low vertical relief and small areal extent. The significant acquisition costs of multifold, 3-D seismic surveys led us to design, acquire, process, and interpret single‐fold 3-D surveys to disclose these subtle, small structures. Augmented conventional 48-channel vibroseis crews collected the 3-D data. Near‐surface glacial till deposits in the area created residual statics and normal‐moveout problems on the single‐fold data. These processing problems were handled by constraining the statics and normal‐moveout velocity solutions with plausible geologic conditions: the near‐flat attitude of the reflecting beds, and the inferred horizontal simplicity of the earth velocity field. Our geologically constrained processing methods included: single‐event correlation picking, single‐fold, surface‐consistent statics, and velocity interpolation on flattened events. In addition, spatially oriented six‐fold stacking increases the signal‐to‐noise ratio in areas where poor signal quality exists. In the case of Northwest Poplar field, geologic studies and subsequent interpretations involving isochron mapping techniques showed that the absence of Mississippian evaporites and paleostructural thinning produce disruption of evaporite events and interval thinning near the evaporites, respectively. Long Creek West field exhibited the interval thickening below, and the interval thinning above the trap formed by two‐stage evaporite solution. Careful analysis of geologic conditions coupled with single‐fold 3-D methods makes it possible to economically explore for small undiscovered structural traps in a mature exploration area.

scholarly journals Detecting clandestine tunnels by using near-surface seismic techniques

2021 ◽  
Author(s):  
Steven Sloan ◽  
Shelby Peterie ◽  
Richard Miller ◽  
Julian Ivanov ◽  
J. Schwenk ◽  
...  
Keyword(s):  
Surface Wave ◽  
Wave Diffraction ◽  
Seismic Data ◽  
Body Wave ◽  
Test Site ◽  
Compressional Wave ◽  
Complex Problem ◽  
Unconsolidated Sediments ◽  
Near Surface ◽  
Reliable Solution

Geophysical detection of clandestine tunnels is a complex problem that has been met with limited success. Multiple methods have been applied spanning several decades, but a reliable solution has yet to be found. This report presents shallow seismic data collected at a tunnel test site representative of geologic settings found along the southwestern U.S. border. Results demonstrate the capability of using compressional wave diffraction and surface-wave backscatter techniques to detect a purpose-built subterranean tunnel. Near-surface seismic data were also collected at multiple sites in Afghanistan to detect and locate subsurface anomalies (e.g., data collected over an escape tunnel discovered in 2011 at the Sarposa Prison in Kandahar, Afghanistan, which allowed more than 480 prisoners to escape, and data from another shallow tunnel recently discovered at an undisclosed location). The final example from Afghanistan is the first time surface-based seismic methods have detected a tunnel whose presence and location were not previously known. Seismic results directly led to the discovery of the tunnel. Interpreted tunnel locations for all examples were less than 2 m of the actual location. Seismic surface wave backscatter and body-wave diffraction methods show promise for efficient data acquisition and processing for locating purposefully hidden tunnels within unconsolidated sediments.

Imaging with deep‐water multiples

Geophysics ◽  
1991 ◽  
Vol 56 (7) ◽  
pp. 1081-1086 ◽  
Author(s):  
Edmund C. Reiter ◽  
M. Nafi Toksöz ◽  
Timothy H. Keho ◽  
G. M. Purdy
Keyword(s):  
Water Column ◽  
Deep Water ◽  
Signal To Noise Ratio ◽  
Synthetic Data ◽  
Ocean Bottom ◽  
Surface Source ◽  
Near Surface ◽  
True Path ◽  
Air Gun ◽  
Useful Signal

Acquisition of on‐bottom hydrophone data recording of a near‐surface source provides an opportunity to treat water column multiples as useful signal. A ray‐equation based Kirchhoff depth migration is used to image primary reflections and deep‐water multiples recorded on an Ocean Bottom Hydrophone (OBH). The image of the subbottom sediments is shown to be improved by inclusion of the deep‐water multiple in the imaging process. Field data, jointly acquired by Woods Hole Oceanographic Institute and University of Texas Institute for Geophysics at Austin and consisting of an OBH (2300 m depth) recording a 10 800 cubic inch air gun array, are used to illustrate the feasibility of the technique. Images are obtained from both the primary reflections and from energy that has undergone an additional passage through the water column. Comparison of these images reveals an excellent correlation of reflectors with the predicted polarity reversal observed in the multiple’s image. Synthetic data are used to examine the difficulties in identifying the true path of the water column multiple. For flat‐layered media there are two different multiple paths — one that reflects beneath the source and one that reflects over the receiver — which have identical traveltimes. They do not, however, have the same amplitude, and it can be shown that their amplitudes differ sufficiently to allow a reliable image to be extracted from the energy that reflects over the receiver. As a final step, the image obtained from the multiple is corrected for the π phase shift from the free surface and added to the image from the primary reflection. This approach is limited to areas where water depths allow reliable separation of primary reflections from water column multiples. Application of this technique allows the utilization of coherent deep water multiples and results in both extended lateral coverage and an increased signal‐to‐noise ratio in the final image.

Computer Application in Geosciences: Imaging of the Subsurface by Structural Coupled Inversion of Potential Field Data

2014 ◽  
Vol 644-650 ◽  
pp. 2670-2673
Author(s):  
Jun Wang ◽  
Xiao Hong Meng ◽  
Fang Li ◽  
Jun Jie Zhou
Keyword(s):  
Potential Field ◽  
Field Data ◽  
Gravity Data ◽  
Computer Application ◽  
Magnetic Data ◽  
Imaging Method ◽  
Inversion Algorithm ◽  
Constant Property ◽  
Near Surface ◽  
Potential Field Data

With the continuing growth in influence of near surface geophysics, the research of the subsurface structure is of great significance. Geophysical imaging is one of the efficient computer tools that can be applied. This paper utilize the inversion of potential field data to do the subsurface imaging. Here, gravity data and magnetic data are inverted together with structural coupled inversion algorithm. The subspace (model space) is divided into a set of rectangular cells by an orthogonal 2D mesh and assume a constant property (density and magnetic susceptibility) value within each cell. The inversion matrix equation is solved as an unconstrained optimization problem with conjugate gradient method (CG). This imaging method is applied to synthetic data for typical models of gravity and magnetic anomalies and is tested on field data.

Investigation of surface and near-surface effects on hydrogen desorption kinetics of MgH2

2014 ◽  
Vol 39 (2) ◽  
pp. 862-867 ◽  
Author(s):  
Sandra Kurko ◽  
Igor Milanović ◽  
Jasmina Grbović Novaković ◽  
Nenad Ivanović ◽  
Nikola Novaković
Keyword(s):  
Surface Effects ◽  
Hydrogen Desorption ◽  
Desorption Kinetics ◽  
Near Surface ◽  
Kinetics Of

Preliminary field data of selected deep-rooted vegetation effects on the slope-vegetation-atmosphere interaction: results from an in-situ test 

2021 ◽  
Author(s):  
Vito Tagarelli ◽  
Federica Cotecchia ◽  
Osvaldo Bottiglieri
Keyword(s):  
Soil Water ◽  
Pore Water ◽  
Field Data ◽  
Test Site ◽  
Grass Species ◽  
In Situ Test ◽  
South Eastern ◽  
Atmosphere Interaction ◽  
The Stability

<p>The soil-vegetation-atmosphere interaction is becoming more and more the subject of intense scientific research, motivated by the wish of using smart vegetation implants as sustainable mitigation measure for erosive phenomena and slope instability processes. <br>The use of novel naturalistic interventions making use of vegetation has been already proven to be successful in the reduction of erosion along sloping grounds, or in increasing the stability of the shallow covers of slopes, whereas the success of vegetation as slope stabilization measure still needs to be scientifically proven for slopes location of deep landslides, whose current activity is climate-induced, as frequent in the south-eastern Apennines. Recently, though, peculiar natural perennial grass species, which develop deep root systems, have been found to grow in the semi-arid climate characterizing the south-eastern Apennines and to determine a strong transpirative flow. Therefore, their peculiar leaf architecture, their crop density, combined with their perennial status and transpiration capacity, make such grass species suitable for the reduction of the net infiltration rates, equal to the difference between the rainfall rate and the sum of the runoff plus the evapotranspiration rate. As such, the grass species here of reference have been selected as vegetation measure intended to determine a reduction of the piezometric levels in the slope down to large depths, in order to increase the stability of deep landslide bodies. <br>At this stage, only preliminary field data representing the interaction of clayey soils with the above cited vegetation species are available. These have been logged within a full scale in-situ test site, where the deep-rooted crop spices have been seeded and farmed. The test site (approximatively 2000 m<sup>2</sup>) has been set up in the toe area of the climate-induced Pisciolo landslide, in the eastern sector of the Southern Apennines.<br>The impact of the vegetation on the hydro-mechanical state of the soil is examined in terms of the spatial and temporal variation of the soil water content, suction an pore water pressure from ground level down to depth, both within the vegetated test site and outside it, where only spare wild vegetation occur, in order to assess the effects of the implant of the selected vegetation. The soil water contents, suctions and pore water pressures have been also analyzed taking into account of the climatic actions, monitored by means of a meteorological station. </p>

Aftershocks of the Benham nuclear explosion

1969 ◽  
Vol 59 (6) ◽  
pp. 2271-2281
Author(s):  
R. M. Hamilton ◽  
J. H. Healy
Keyword(s):  
Fault Plane ◽  
Nuclear Explosion ◽  
Test Site ◽  
Strike Slip ◽  
Nevada Test Site ◽  
Ground Zero ◽  
Fault Plane Solutions ◽  
Fault Movement ◽  
Near Surface ◽  
Earthquake Distribution

abstract The Benham nuclear explosion, a 1.1 megaton test 1.4 km beneath Pahute Mesa at the Nevada Test Site, initiated a sequence of earthquakes lasting several months. The epicenters of these shocks were located within 13 km of ground zero in several linear zones that parallel the regional fault trends. Focal depths range from near surface to 6 km. The earthquakes are not located in the zone of the major ground breakage. The earthquake distribution and fault plane solutions together indicate that both right-lateral strike-slip fault movement and dip-slip fault movement occurred. The explosion apparently caused the release of natural tectonic strain.

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