1978 Houston-Galveston and Texas Gulf Coast vertical-control surveys (open access)

1978 Houston-Galveston and Texas Gulf Coast vertical-control surveys

Comparisons between leveling surveys of different epochs are used to determine vertical displacement of permanent bench marks. Displacement of bench marks usually represents the movement of the surrounding area. In this report, the 1978 Houston-Galveston and Texas Gulf Coast releveling surveys are compared to the 1963, 1973, and 1976 releveling results. The changes in elevations of bench marks common to two or more epochs are tabulated and plotted in Appendix A. From these differences, contour maps were prepared for the 1963 to 1978 and 1973 to 1978 epochs in the 2/sup 0/ x 2/sup 0/ area of maximum subsidence. Annual subsidence rates computed for the 1973 to 1978 period are about 25% less in the maximum subsidence area than the rates computed for the 1963 to 1973 period.
Date: November 1, 1980
Creator: Balazs, E. I.
Object Type: Report
System: The UNT Digital Library
Borehole Seismic Monitoring of Injected CO2 at the Frio Site (open access)

Borehole Seismic Monitoring of Injected CO2 at the Frio Site

As part of a small scale sequestration test (about 1500 tonsof CO2) in a saline aquifer, time-lapse borehole seismic surveys wereconducted to aid in characterization of subsurface CO2 distribution andmaterial property changes induced by the injected CO2. A VSP surveydemonstrated a large increase (about 75 percent) in seismic reflectivitydue to CO2 injection and allowed estimation of the spatial extent of CO2induced changes. A crosswell survey imaged a large seismic velocitydecrease (up to 500 m/s) within the injection interval and provided ahigh resolution image of this velocity change which maps the subsurfacedistribution of CO2 between two wells. Numerical modeling of the seismicresponse uses the crosswell measurements to show that this small CO2volume causes a large response in the seismic reflectivity. This resultdemonstrates that seismic detection of small CO2 volumes in salineaquifers is feasible and realistic.
Date: April 21, 2006
Creator: Daley, Thomas M.; Myer, Larry R.; Hoversten, G.M.; Peterson, JohnE. & Korneev, Valeri A.
Object Type: Article
System: The UNT Digital Library
Observations of heavy energetic ions for upstream from comet Halley (open access)

Observations of heavy energetic ions for upstream from comet Halley

On March 25, 1986, the ICE spacecraft came within 28 x 10/sup 6/ km of the nucleus of comet Halley. For several days around this time, bursts of heavy ions were observed by the ICE energetic ion experiment. These bursts were observed only during periods when the solar wind velocity was considerably higher than its nominal value. We examine the characteristics of these ions, in particular their anisotropies. Using the well known formulae for transformation of distributions from the solar wind frame of reference to the spacecraft frame, we examine the angular distributions expected from either protons, or heavy ions from the water group, and show that the measurements are consistent with heavy ions, and not with protons. We discuss other sources of heavy ions and conclude that the most likely source of these ions is comet Halley. 9 refs., 5 figs.
Date: January 1, 1986
Creator: Sanderson, T. R.; Wenzel, K. P.; Daly, P. W.; Cowley, S. W. H.; Hynds, R. J.; Richardson, I. G. et al.
Object Type: Article
System: The UNT Digital Library