An Appraisal of a New Generation of Surface Wave Techniques at a Test Site in Florida

IFCEE 2015 ◽  
2015 ◽  
Author(s):  
Pengxiang Jiang ◽  
Khiem T. Tran ◽  
Dennis R. Hiltunen ◽  
Nick Hudyma
Keyword(s):  
Surface Wave ◽  
Test Site ◽  
New Generation

Combining surface-wave phase-velocity dispersion curves and full microtremor horizontal-to-vertical spectral ratio for subsurface sedimentary site characterization

2016 ◽  
Vol 4 (4) ◽  
pp. SQ41-SQ49 ◽  
Author(s):  
Agostiny Marrios Lontsi ◽  
Matthias Ohrnberger ◽  
Frank Krüger ◽  
Francisco José Sánchez-Sesma
Keyword(s):  
Surface Wave ◽  
Phase Velocity ◽  
Velocity Dispersion ◽  
Spectral Ratio ◽  
Test Site ◽  
Dispersion Curves ◽  
Surface Velocity ◽  
Wave Phase ◽  
Phase Velocity Dispersion ◽  
Wave Phase Velocity

We compute seismic velocity profiles by a combined inversion of surface-wave phase-velocity dispersion curves together with the full spectrum of the microtremor horizontal-to-vertical (H/V) spectral ratio at two sediment-covered sites in Germany. The sediment deposits are approximately 100 m thick at the first test site and approximately 400 m thick at the second test site. We have used an extended physical model based on the diffuse wavefield assumption for the interpretation of the observed microtremor H/V spectral ratio. The extension includes the interpretation of the microtremor H/V spectral ratio observed at depth (in boreholes). This full-wavefield approach accounts for the energy contribution from the body and surface waves, and thus it allows for inverting the properties of the shallow subsurface. We have obtained the multimode phase velocity dispersion curves from an independent study, and a description of the extracted branches and their interpretation was developed. The inversion results indicate that the combined approach using seismic ambient noise and actively generated surface-wave data will improve the accuracy of the reconstructed near-surface velocity model, a key step in microzonation, geotechnical engineering, seismic statics corrections, and reservoir imaging.

A method for relocating seismic events using surface waves

1973 ◽  
Vol 63 (4) ◽  
pp. 1305-1313
Author(s):  
S. T. Crough ◽  
R. Van der Voo
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Group Velocity ◽  
Group Velocity Dispersion ◽  
Body Wave ◽  
Test Site ◽  
Seismic Events ◽  
Computer Technique ◽  
Nuclear Explosions ◽  
Reference Event

abstract Seismic events can be relocated relative to a reference event by using the group-velocity dispersion curves of surface waves. Since group velocity is a function of the travel path, surface waves from two events in the same locale should show identical group velocities when viewed at any one seismograph station. A computer technique has been developed for comparing the group-velocity curves of any event with the curves of a reference event and for determining the relocation which causes the curves to best coincide. The method is evaluated by relocating eight intermediate-size nuclear explosions of the Nevada Test Site series. With precise curve fitting, the surface-wave locations are slightly more accurate in southern Nevada than the standard body-wave determinations. The surface-wave origin times are considerably more accurate. In areas of sparse station coverage or of many small earthquakes, the surface-wave method can be expected to improve seismic locations significantly.

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.

scholarly journals Theoretical and observed distance corrections for Rayleigh-wave magnitude

1972 ◽  
Vol 62 (6) ◽  
pp. 1611-1619 ◽  
Author(s):  
R. W. Alewine
Keyword(s):  
Surface Wave ◽  
Energy Dissipation ◽  
Rayleigh Wave ◽  
Test Site ◽  
Nevada Test Site ◽  
Surface Wave Magnitude ◽  
Dissipation Coefficient ◽  
Distance Relation ◽  
Energy Dissipation Coefficient ◽  
Distance Correction

abstract Examination of the distance correction factor used in the widely accepted formula for surface-wave magnitude reveals that this empirically derived linear formula fails to give an accurate approximation to the theoretical nonlinear amplitude-distance relation for epicentral distances less than 15°. For epicentral distances greater than 15°, the empirical formula contains an implied oceanic-type energy-dissipation coefficient. When the original Gutenberg theoretical surface-wave magnitude formula with an appropriate continental energy-dissipation coefficient is applied to explosion data from the Nevada Test Site, a consistent surface-wave magnitude is obtained at all distances. A systematic method of normalizing Rayleigh-wave magnitudes obtained over different types of propagation paths is suggested. This normalization might provide a means for better separating natural events and explosions in the mb—Ms plots.

Canadian detection and discrimination thresholds for earthquakes and underground explosions in Asia

1969 ◽  
Vol 6 (6) ◽  
pp. 1455-1458 ◽  
Author(s):  
P. W. Basham
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Central Asia ◽  
Body Wave ◽  
Test Site ◽  
Discrimination Threshold ◽  
Nevada Test Site ◽  
Novaya Zemlya ◽  
Seismograph Network

A suite of 33 Asian earthquakes and 36 Central Asia and Novaya Zemlya underground explosions are used to define the minimum detection levels in terms of surface-wave and body-wave magnitudes and the discrimination thresholds of the M versus m discriminant for the Canadian seismograph network. Under low microseismic noise conditions surface-waves can be observed for earthquakes down to m 4.9 and explosions down to m 5.9 for the region near the central Asia test sites. For events above these magnitudes, the M versus m relationships provide reliable discrimination between earthquakes and explosions. Comparison with an intracontinental study leads to the conclusion that the discrimination threshold is limited by path effects and greater distances to events about m 1.0 larger near the Asian test sites than near the Nevada test site.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

Total etch dentin bonding systems: scanning electron microscopy of the resin-dentin hybrid layer

1992 ◽  
Vol 50 (2) ◽  
pp. 1092-1093
Author(s):  
Jorge Perdigao
Keyword(s):  
Composite Resin ◽  
Mechanical Interlocking ◽  
Hybrid Layer ◽  
Agent Based ◽  
Dentin Bonding ◽  
Acid Agent ◽  
Bond Strengths ◽  
Main Component ◽  
Bonding Systems ◽  
New Generation

In 1955, Buonocore introduced the etching of enamel with phosphoric acid. Bonding to enamel was created by mechanical interlocking of resin tags with enamel prisms. Enamel is an inert tissue whose main component is hydroxyapatite (98% by weight). Conversely, dentin is a wet living tissue crossed by tubules containing cellular extensions of the dental pulp. Dentin consists of 18% of organic material, primarily collagen. Several generations of dentin bonding systems (DBS) have been studied in the last 20 years. The dentin bond strengths associated with these DBS have been constantly lower than the enamel bond strengths. Recently, a new generation of DBS has been described. They are applied in three steps: an acid agent on enamel and dentin (total etch technique), two mixed primers and a bonding agent based on a methacrylate resin. They are supposed to bond composite resin to wet dentin through dentin organic component, forming a peculiar blended structure that is part tooth and part resin: the hybrid layer.

Low-voltage, high-resolution scanning electron microscopy of polymers

1987 ◽  
Vol 45 ◽  
pp. 466-467 ◽  
Author(s):  
S. J. Krause ◽  
W.W. Adams ◽  
S. Kumar ◽  
T. Reilly ◽  
T. Suziki
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Resolution Limit ◽  
Crossover Point ◽  
New Generation ◽  
Beam Damage ◽  
Scanning Electron

Scanning electron microscopy (SEM) of polymers at routine operating voltages of 15 to 25 keV can lead to beam damage and sample image distortion due to charging. Imaging polymer samples with low accelerating voltages (0.1 to 2.0 keV), at or near the “crossover point”, can reduce beam damage, eliminate charging, and improve contrast of surface detail. However, at low voltage, beam brightness is reduced and image resolution is degraded due to chromatic aberration. A new generation of instruments has improved brightness at low voltages, but a typical SEM with a tungsten hairpin filament will have a resolution limit of about 100nm at 1keV. Recently, a new field emission gun (FEG) SEM, the Hitachi S900, was introduced with a reported resolution of 0.8nm at 30keV and 5nm at 1keV. In this research we are reporting the results of imaging coated and uncoated polymer samples at accelerating voltages between 1keV and 30keV in a tungsten hairpin SEM and in the Hitachi S900 FEG SEM.

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