A field test of an electrodeless arc discharge, borehole seismic source

Geophysics ◽  
1993 ◽  
Vol 58 (11) ◽  
pp. 1558-1564 ◽  
Author(s):  
Kenneth D. Mahrer ◽  
Brian J. Zook
Keyword(s):  
Field Test ◽  
Arc Discharge ◽  
Sensor Arrays ◽  
Seismic Source ◽  
Test Site ◽  
Near Surface ◽  
Single Firing ◽  
Borehole Seismic ◽  
High Degree ◽  
Repeatability Test

Waveforms generated by an impulsive, 1.2 kJ, seven‐conductor wireline electrodeless arc discharge borehole seismic source or sparker at Texaco’s Humble, TX field test site were recorded by three borehole sensor arrays: two free‐hanging hydrophone streamers in in‐line boreholes at 82 m and 170 m from the source well and a grouted, three‐component geophone string in a borehole 110 m from the source well. A repeatability test of the source, consisting of single firings of the source at a rate of 1 firing per 5 s, showed very clean, very strong, Ricker‐like wavelets. Despite a high‐degree of attenuation (exact value of Q is not known), the useful frequency passband of the wavelets was from 200 Hz to 1200 Hz for the data recorded by the 82-m offset hydrophones and 200 Hz to 500 Hz for the 170-m hydrophones. Using 62 single‐firing wavelets recorded in the 82-m offset well gave mean and median crosscorrelations greater than 0.96 with standard deviations less than 0.02. A stack test, consisting of 1, 2, 4, 8, 16, and 32-stacked waveforms, confirmed the shape, strong S/N ratio, and high correlation of the sparker output. The 32-stack, which took less than 3 minutes to generate, was recorded by the noisy, near-surface geophones at a raypath distance of nearly 300m.

scholarly journals Field comparison of shallow seismic sources near Chino, California

Geophysics ◽  
1992 ◽  
Vol 57 (5) ◽  
pp. 693-709 ◽  
Author(s):  
Richard D. Miller ◽  
Susan E. Pullan ◽  
Don W. Steeples ◽  
James A. Hunter
Keyword(s):  
Water Table ◽  
Seismic Source ◽  
Test Site ◽  
Single Site ◽  
Seismic Sources ◽  
Near Surface ◽  
Shallow Seismic ◽  
Site Characteristics ◽  
Weight Drop ◽  
Different Sources

Data from a shallow seismic‐source comparison test conducted in an area with a water‐table depth in excess of 30 m and near‐surface velocities less than 330 m/s were acquired from 13 different sources at a single site near Chino, California. The sources included sledgehammer, explosives, weight drop, projectile impacts, and various buffalo guns. A possible reflecting event can be interpreted at about 70 ms. At this particular test site, the lowly sledgehammer is among the best sources to provide data to see the possible reflection. Our previous work and that of our colleagues suggests that any source could dominate the comparison categories addressed here, given the appropriate set of site characteristics.

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.

scholarly journals Investigating the Performance of Bi-Static GPR Antennas for Near-Surface Object Detection

Sensors ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 170 ◽  
Author(s):  
Xianyang Gao ◽  
Frank J. W. Podd ◽  
Wouter Van Verre ◽  
David J. Daniels ◽  
Anthony J. Peyton
Keyword(s):  
Ground Penetrating Radar ◽  
Input Impedance ◽  
Test Site ◽  
Late Time ◽  
Near Surface ◽  
Object Depth ◽  
Ground Penetrating ◽  
Antenna Input ◽  
Surface Object ◽  
Bow Tie

Antennas are an important component in ground penetrating radar (GPR) systems. Although there has been much research reported on the design of individual antennas, there is less research reported on the design of the geometry of bi-static antennas. This paper considers the effects of key parameters in the setup of a GPR head consisting of a bi-static bow-tie pair to show the effect of these parameters on the GPR performance. The parameters investigated are the antenna separation, antenna height above the soil, and antenna input impedance. The investigation of the parameters was performed by simulation and measurements. It was found when the bi-static antennas were separated by 7 cm to 9 cm and were operated close to the soil (2 cm to 4 cm), the reflected signal from a near-surface object is relatively unaffected by height variation and object depth. An antenna input impedance of 250 Ω was chosen to feed the antennas to reduce the late-time ringing. Using these results, a new GPR system was designed and then evaluated at a test site near Benkovac, Croatia.

scholarly journals Large Volume of CO2 Injection at the Cranfield, Early Field Test of the SECARB Phase III: Near-Surface Monitoring

2012 ◽  
Author(s):  
Changbing Yang ◽  
Katherine D. Romanak ◽  
Robert M. Holt ◽  
Jeff Lindner ◽  
Laura Smith ◽  
...  
Keyword(s):  
Field Test ◽  
Large Volume ◽  
Phase Iii ◽  
Co2 Injection ◽  
Near Surface ◽  
Surface Monitoring

Heteroepitaxial Growth Of ZnO Films BY PLD

1997 ◽  
Vol 474 ◽  
Author(s):  
R. D. Vispute ◽  
V. Talyansky ◽  
Z. Trajanovic ◽  
S. Choopun ◽  
M. Downes ◽  
...  
Keyword(s):  
Oxygen Pressure ◽  
Surface Region ◽  
Optical Quality ◽  
Degree Of Crystallinity ◽  
Zno Films ◽  
Heteroepitaxial Growth ◽  
Near Surface ◽  
Ion Channeling ◽  
Deposition Parameters ◽  
High Degree

ABSTRACTHere we present our recent work on the fabrication of high crystalline and optical quality ZnO films on sapphire (001) by pulsed laser deposition. The influence of deposition parameters such as the substrate temperature, oxygen pressure, laser fluence, and pulse repetition rate on the crystalline quality of ZnO layers has been studied. The Ω-rocking curve FWHM of the (002) peak for the films grown at 750°, oxygen pressure 10−5 Torr was 0.17°. The XRD-Ф scans studies revealed that the films were epitaxial with a 30° rotation of the unit cell with respect to the sapphire to achieve a low energy configuration for epitaxial growth. The high degree of crystallinity was confirmed by ion channeling technique providing a minimum Rutherford backscattering yield of 2–3% in the near surface region (-2000Å). The atomic force microscopy revealed smooth hexagonal faceting of the films. The optical absorption edge measured by UV-Visible spectroscopy was sharp at 383 nm. Excellent crystalline properties of these epi-ZnO/sapphire heterostractures are thus promising for III-V nitride heteroepitaxy.

scholarly journals Estimation of near-surface attenuation in the tectonically complex contact area of the Northwestern External Dinarides and the Adriatic foreland

2019 ◽  
Author(s):  
Snježana Markušić ◽  
Davor Stanko ◽  
Tvrtko Korbar ◽  
Ivica Sović
Keyword(s):  
Amplitude Spectrum ◽  
Seismic Source ◽  
Propagation Path ◽  
Site Conditions ◽  
Coda Q ◽  
Near Surface ◽  
Contour Lines ◽  
Geological Features ◽  
A Site ◽  
External Dinarides

Abstract. Seismic-induced ground motion at a site is generally influenced by seismic source, propagation path and local site conditions. Over the last several decades, researchers have consistently asserted that for near site attenuation, the spectral parameter kappa is subject primarily to site conditions. In this research we estimated parameter kappa based on the acceleration amplitude spectrum of shear waves, from the selected recordings of local earthquakes from seismological stations situated in the western part of Croatia from the slope of the high-frequency part. The spatial distribution of individual kappa values is compared with the azimuthal distribution of earthquake epicentres, with Vs30 values and the published coda-Q values for each station, as well as with isoseismal maps for several stronger events in the investigated area, along with the geological features. The dextral shift of crustal segments and frontal thrust of the External Dinarides along the Kvarner fault zone has probably had an impact on the geometry of the kappa parameter contour lines. These results are important for gaining further insight into the attenuation of near-surface crust layers in the Northwestern External Dinarides and the associated Adriatic foreland, as well as in similar geotectonic settings.

Crosswell seismic imaging in a contaminated basalt aquifer

Geophysics ◽  
2004 ◽  
Vol 69 (1) ◽  
pp. 16-24 ◽  
Author(s):  
Thomas M. Daley ◽  
Ernest L. Majer ◽  
John E. Peterson
Keyword(s):  
Seismic Source ◽  
P Wave ◽  
Low Velocity ◽  
S Waves ◽  
High Attenuation ◽  
Well Spacing ◽  
Simultaneous Acquisition ◽  
Environmental Laboratory ◽  
New Type ◽  
Borehole Seismic

Multiple seismic crosswell surveys have been acquired and analyzed in a fractured basalt aquifer at Idaho National Engineering and Environmental Laboratory. Most of these surveys used a high‐frequency (1000–10,000 Hz) piezoelectric seismic source to obtain P‐wave velocity tomograms. The P‐wave velocities range from less than 3200 m/s to more than 5000 m/s. Additionally, a new type of borehole seismic source was deployed as part of the subsurface characterization program at this contaminated groundwater site. This source, known as an orbital vibrator, allows simultaneous acquisition of P‐ and S‐waves at frequencies of 100 to 400 Hz, and acquisition over larger distances. The velocity tomograms show a relationship to contaminant transport in the groundwater; zones of high contaminant concentration are coincident with zones of low velocity and high attenuation and are interpreted to be fracture zones at the boundaries between basalt flows. The orbital vibrator data show high Vp/Vs values, from 1.8 to 2.8. In spite of the lower resolution of orbital vibrator data, these data were sufficient for constraining hydrologic models at this site while achieving imaging over large interwell distances. The combination of piezoelectric data for closer well spacing and orbital vibrator data for larger well spacings has provided optimal imaging capability and has been instrumental in our understanding of the site aquifer's hydrologic properties and its scale of heterogeneity.

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