scholarly journals GEOPHYSICAL DATA ON THE CLIMAX STOCK, NEVADA TEST SITE, NYE COUNTY, NEVADA

Geophysics ◽  
1962 ◽  
Vol 27 (5) ◽  
pp. 599-610 ◽  
Author(s):  
John W. Allingham ◽  
Isidore Zietz
Keyword(s):  
Atomic Energy Commission ◽  
Three Dimensional ◽  
Test Site ◽  
Seismic Effect ◽  
Nevada Test Site ◽  
Aeromagnetic Survey ◽  
Surface Samples ◽  
Welded Tuff ◽  
Geophysical Surveys ◽  
Paleozoic Rocks

A granitic stock at Oak Spring, Nevada, was selected in 1960 by the Atomic Energy Commission as a possible site to study the seismic effect of a deep nuclear shot contained in a large volume of rock. Geophysical surveys were conducted to determine the general configuration of the stock, particularly the thickness. The stock intrudes a sequence of carbonate and siliceous sedimentary rocks of Paleozoic age, which are overlain by Tertiary pyroclastic rocks consisting of tuff, welded tuff, and breccia. A three‐dimensional analysis of a detailed aeromagnetic survey indicates that the stock has a shape similar to a truncated cone, the diameter of which increases from about one mile at the surface to at least 6 miles near sea level, 5,000 feet beneath the surface. The stock, therefore, is much larger than indicated by the area of [Formula: see text] square miles exposed at the surface. In addition, computations show that the intrusion has a thickness of at least 13,000 ft. Much of the ambiguity of interpretation was removed from the analysis because susceptibility measurements of cores from recent drilling and remanent magnetization data from surface samples were available. Interpretation of a gravity profile over the stock gives the probable thickness of the overlying alluvial fill and buried tuff, but does not delineate the intrusive from the Paleozoic rocks.

Application of three-dimensional kinematic imaging to analysis of seismic reflection data from the Nevada Test Site

1984 ◽  
Vol 74 (6) ◽  
pp. 2187-2199
Author(s):  
Jing Wen ◽  
George A. McMechan
Keyword(s):  
Grid Point ◽  
Three Dimensional ◽  
Real Data ◽  
Test Site ◽  
Three Dimensions ◽  
Seismic Survey ◽  
Nevada Test Site ◽  
Seismic Reflection Data ◽  
Reflector Surface ◽  
Best Fit

Abstract Three-dimensional kinematic migration produces a “best-fit” migrated surface, in three-dimensions, of any chosen reflector. The data are the travel times of all observed reflections and diffractions produced by the reflector. Source/receiver configurations are arbitrary, but should be arranged to provide good spatial sampling of the reflector. Each observation contributes an ellipsoid containing all possible reflection points. From this family of ellipsoids, the optimal reflector surface (the envelope of the family) is estimated by use of a statistical imaging condition. The “best-fit” position and shape of the reflector surface is obtained by defining a regular (x, y) grid over the region of interest and estimating the reflector depth beneath each grid point from the distribution of ellipsoids that are present there. The imaging criterion is implemented at each grid point by convolution of a Gaussian with the vector of ellipsoid depths. The width of the Gaussian is chosen to correspond to the scale of the features one wishes to resolve in the image. For each grid point, the migrated image is located at the depth at which the convolution is a maximum. The algorithm is applied to both synthetic and real data. The synthetic data are constructed by ray tracing in a known structure. The real data are from a seismic survey at the Nevada Test Site; here, a reflector is imaged and interpreted as the surface of a high velocity Paleozoic dolomite that is overlain by low-velocity tuffs.

Effect of a fault on explosion-generated ground shock spectra

1968 ◽  
Vol 58 (6) ◽  
pp. 2033-2041
Author(s):  
Frank W. Galbraith
Keyword(s):  
Fault Zone ◽  
High Frequency ◽  
Atomic Energy Commission ◽  
Ground Surface ◽  
Test Site ◽  
Underground Nuclear Explosion ◽  
Nevada Test Site ◽  
High Frequency Response ◽  
The North ◽  
Ground Shock

ABSTRACT Shock spectrum measurements were made for an underground nuclear explosion at the Nevada Test Site of the U. S. Atomic Energy Commission using 29 reed gages. The objective of the measurements was to determine the effect of a fault zone on shock spectra measured at the ground surface and generated by the explosion. The reed gages were located along two gage lines; one extended to the west and crossed the fault at right angles. The other gage line extended to the north and was generally parallel to the fault. The results showed that the fault zone had an effect on vertical spectra but not on horizontal radial spectra. The vertical gage directly on the fault showed significantly lower displacements for all frequencies above 3 cycles per second but showed no apparent effect on the 3 cps displacement. For gages beyond the fault the vertical spectra for frequencies higher than 3 cps were greater than for corresponding gages along the north gage line. It is believed that this was caused by the upthrust base rock on the side of the fault away from the explosion with a resultant decreased thickness of tuff and alluvium. This resulted in less attenuation of high frequency response than was expected.

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