Graduation date: 1992

Knowledge of fracture orientation and density is significant for reservoir and aquifer characterization. In this study, field experiments are designed to estimate fracture parameters in situ from seismic and GPR (radar) data. The seismic experiment estimates parameters of orientation, density, and filling material. The GPR experiment estimates channel flow geometry and aperture. In the seismic study, lines of 2D data are acquired in a vertically fractured limestone at three different azimuths to look for differences in seismic velocities. A sledgehammer, vertical source and a multicomponent, Vibroseis source are used with multicomponent receivers. Acquisition parameters of frequency, receiver spacing and source-to-receiver offset are varied. The entire suite of seismic body waves and Rayleigh waves is analyzed to characterize the subsurface. Alford rotations are used to determine fracture orientation and demonstrate good results when geophone orientation is taken into account. Results indicate that seismic anisotropy is caused by regional faulting. Average fracture density of less than 5% and water table depth estimates are consistent with field observations. Groundwater flow direction has been observed by others to cross the fault trend and is subparallel to a secondary fracture set. In this study, seismic anisotropy appears unrelated to this secondary fracture set. Vp/Vs and Poisson's ratio values indicate a dolomite lithology. Sledgehammer and Vibroseis data provide consistent results. In the GPR experiment, reflection profiles are acquired through common-offset profiling perpendicular to the dominant flow direction. High frequency waves are used to delineate fluid flow paths through a subhorizontal fracture and observe tracer channeling. Channeling of flow is expected to control solute transport. Changes in radar signal are quantitatively associated with changes in fracture filling material from an innovative method using correlation coefficients. Mapping these changes throughout the survey area reveals the geometry of the flow path of each injected liquid. The tracer is found to be concentrated in the center of the survey area where fracture apertures are large. This demonstrates that spatial variations in concentration are controlled by fluid channel geometry.

The Picacho earth fissure transects subsiding alluvial sediments near the eastern periphery of the Picacho basin in southcentral Arizona. The basin has undergone land subsidence of as much as 3.8 m since the 1930's due to compaction of the aquifer system in response to ground-water-level declines that have exceeded 100 m. The fissure extends generally north-south for 15 km and exhibits horizontal tensile failure as well as up to 0.6 m of normal dip-slip movement at the land surface, with the west side of the fissure downthrown. The fissure was observed as early as 1927, following an earthquake, and is the longest earth fissure in Arizona. Vertical and horizontal displacements have been monitored along a line normal to the fissure. The survey line extends from a bedrock outcrop in the Picacho Mountains on the east, past an observation well near the fissure, to a point 1422 in to the west. From May 1980 to May 1984, the western, downthrown side of the fissure subsided 167 ±1.8 mm and moved 18 ±1.5 mm westward into the basin. Concurrently, the eastern, relatively upthrown side subsided 147 ±1.8 mm and moved 14 ±1.5 mm westward. Dislocation modeling of deformation along the survey line near the fissure suggests that dip-slip movement has occurred along a vertical fault surface that extends from the land surface to a depth of about 300 m. Slip was 9 mm from May to December 1980 and 9 mm from March to November 1981. Continuous measurements were made of horizontal movement across the fissure using a buried invar-wire horizontal extensometer, while water-level fluctuations were continuously monitored in four piezometers nested in two observation wells. The range of horizontal movement was 4.620 mm, and the range of water-level fluctuation in the nearest piezometer in the deeper alluvium was 9.05 m. The maximum annual opening of the fissure during the study period was 3.740 mm from March to October 1981, while the water-level declined 7.59 m. The fissure closed 1.033 mm from October 1981 to March 1982 while the water level recovered 6.94 m. Opening and closing of the fissure were smooth and were correlated with water-level decline and recovery, respectively, in the nearby piezometers. Pearson correlation coefficients between the water-level fluctuations in the deeper piezometers and horizontal movement ranged from 0.913 to 0.925. The correlogram of water-level decline as ordinate, versus horizontal strain as abscissa, exhibits hysteresis loops for annual cycles of water-level fluctuation as well as near-vertical excursions for shorter cycles of pumping and recovery.

Fault scarps cutting alluvial deposits define the present-day eastern boundary of Basin and Range faulting in Trans-Pecos Texas. These faults are found in the Salt Basin graben north of Van Horn, Texas, and its southerly extensions along Lobo Valley and Michigan Draw. Discontinuous and en echelon Quaternary fault scarps quickly die out to the south on the eastern side of the graben but become more continuous and develop larger displacements (up to 6 meters) along the west side of Salt Basin at the base of Sierra Diablo. The orientation of the more than one hundred Quaternary down-to-the-basin fault scarps and photolineaments appears to be controlled by pre-existing structural zones of weakness. The preferential alignment of Quaternary (Holocene?) fault scarps along the western side of the graben, the westward shifting of playa lakes and the preferred orientation of giant desiccation polygons show that the graben floor is subsiding more rapidly along the western margin. These faults also separate fresh from saline ground water. Four transverse structural lineaments crossing the northern portion of Salt Basin graben were mapped by P.B. King (1948, 1965) and M. Wiley (1970). A fifth zone, trending east-west between the Babb flexure and Bitterwell Mountain is proposed in this thesis. A tectonic origin is suggested by the orientation of the scarps and the proximity of the Mayfield fault scarps to the estimated epicenters of the 1931 Valentine earthquake. The frequency of small earth tremors felt by the residents of the basin and recorded by temporary seismograph stations indicate tectonic adjustments are presently occurring. / text

published_or_final_version / abstract / Earth Sciences / Master / Master of Philosophy

Thèse (D.R.Min.) -- Université du Québec à Chicoutimi, 1992. / Document électronique également accessible en format PDF. CaQCU

Thèse (D.R.Min.) -- Université du Québec à Chicoutimi, 1992. / These présentée en collaboration de l'Université du Québec à Chicoutimi et Institute of geochemistry, Academia Sinica. CaQCU Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Sc.T.)-- Université du Québec à Chicoutimi, 1993. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Sc.T.)-- Université du Québec à Chicoutimi, 1993. / Document électronique également accessible en format PDF. CaQCU

Thèse (M.Sc.T.) -- Université du Québec à Chicoutimi, 2002. / Bibliogr.: f. 126-136. Document électronique également accessible en format PDF. CaQCU