No description available.

No description available.

No description available.

The goal of Ground Penetrating Radar (GPR) research at the University of Arizona is to improve our understanding use of GPR in a variety of settings. Observations from local surveys will form the basis for developing continuous profiling systems for future terrestrial and extraterrestrial applications. Determining electrical properties of in-situ soils and rock helps predict GPR behavior. A test site was constructed to measure the electrical properties of representative Southern Arizona Basin soils and to quantify the GPR response to these properties. In general, 100 and 300 MHz antennas are useful for surveys designed to locate large anomalies. The higher resolution of the 500 MHz antenna is valuable in most investigations and has been successful in mapping archaeological sites in the region. Signal processing of digitized GPR data clarifies the profile for interpretation and conditions the data for remote interpretation of the GPR profile through neural network pattern recognition of anomalies.

Three electrical and electromagnetic geophysical methods were used to examine the moisture and permeability distribution and identify fractures in a partially saturated, fractured ash-flow tuff near Superior, Arizona. Experiments using ground penetrating radar (GPR) to locate targets with known orientations in the tuff were used to assess the angular limits of fracture detection from radar profiles. Identification of fractures from radar records appears to be limited to those with dips of less than 45°. The application of a single well electrical tracer (SWET) technique proved effective in identifying relative permeability in a borehole drilled in the tuff when compared to air permeability logs of the same borehole. Laboratory resistivity measurements of electrical resistivity were conducted to determine electrical resistivity/moisture saturation relationships. Twenty-seven tuff cores were measured at equilibrated suctions of 0 to 500 kPa. Resistivity values ranged from 50 to 1600 ohm-m.

Gravity and magnetic surveys were performed in the northeast portion of the Santa Rita Experimental Range, in southeastern Arizona, to identify faults and gain a better understanding of the subsurface geology. A total of 234 gravity stations were established, and numerous magnetic data were collected with portable and truck-mounted proton precession magnetometers. In addition, one line of very low frequency electromagnetic data was collected together with magnetic data. Gravity anomalies are used to identify two normal faults that project northward toward a previously identified fault. The gravity data also confirm the location of a second previously interpreted normal fault. Interpretation of magnetic anomaly data indicates the presence of a higher-susceptibility sedimentary unit located beneath lower-susceptibility surficial sediments. Magnetic anomaly data identify a 1-km-wide negative anomaly east of these faults caused by an unknown source and reveal the high variability of susceptibility in the Tertiary intrusive rocks in the area.

No description available.

No description available.

Fluid flows involving transport of a liquid phase in close proximity with its solid phase involve continuous transfer of mass and heat, which can influence the nature of the drainage that occurs. We consider mathematical models for two such situations; magma flow in the mantle and water flow beneath glaciers. In part I, we derive a model for porous flow within a partially molten column of mantle undergoing decompression melting. By ignoring composition effects, and by scaling the equations appropriately, approximate analytical solutions can be found for one-dimensional upwelling, which allow the region and extent of melting to be determined. We study the dynamics of open channels of melt flow in the same situation, and find that such channels would have low pressure compared to the surrounding porous flow, and therefore draw in melt from a region of the size of a compaction length. We suggest that such channels could form through the unstable effects of melting caused by heat transfer by the upwelling melt. We emphasise the similarity with channels of meltwater that are known to exist beneath ice. In part II we pose a generalised model for subglacial water flow, which is described as an effective porous medium, the pore space being determined from an evolution equation. This is used to investigate the flow into a channel, which is found to be drawn from a surrounding region whose size, we suggest, determines the spacing between major drainage channels beneath ice sheets. These are compared to the observed spacing of eskers. A critical condition on the discharge necessary to sustain a channel is found, which may provide a criteria to decide where and when channelised drainage occurs. Lastly, a simple drainage model is used to explain seasonal variations in the velocity of a valley glacier.

<p> The seismic attribute High-Frequency Absorption (HFA) is a method of evaluating the absorptive properties of rocks as nonstationary wavelets pass through the substrate. This technique is used today as a direct hydrocarbon indicator, where it should be used as a diagnostic tool in conjunction with several other geophysical and geological processes for the delineation of hydrocarbon reservoirs. Understanding the absorptive properties of target reservoirs and correlating their geophysical aspects to geologic properties, courtesy of well logs, may allow us to interpret patterns between hydrocarbon saturation and HFA on local reservoir scales. The ability to estimate hydrocarbon saturation can significantly affect the risk evaluations of potential prospects and further increase our rate of success when wildcatting or developing fields. Analysis shows that in this particular project, proper data, such as neutron-density logs, are seldom run in the wells of this area, thus making estimation of water/hydrocarbons very difficult and very inaccurate. Other complications include the resolution of seismic data compared to well log data. Due to these obstacles, high-resolution correlations of HFA to hydrocarbon saturation proved to be unsuccessful. However, association of proven vs. false prospects showed very high correlations to HFA signatures.</p>