The attenuation of compressional (P) and shear (S) waves in dry, saturated, and frozen rocks is measured in the laboratory at ultrasonic frequencies. A pulse transmission technique and spectral ratios are used to determine attenuation coefficients and quality factor (Q) values relative to a reference sample with very low attenuation. In the frequency range of about 0.1–1.0 MHz, the attenuation coefficient is linearly proportional to frequency (constant Q) both for P‐ and S‐waves. In dry rocks, [Formula: see text] of compressional waves is slightly smaller than [Formula: see text] of shear waves. In brine and water‐saturated rocks, [Formula: see text] is larger than [Formula: see text]. Attenuation decreases substantially (Q values increase) with increasing differential pressure for both P‐ and S‐waves.

Theoretical models based on several hypothesized attenuation mechanisms are discussed in relation to published data on the effects of pressure and fluid saturation on attenuation. These mechanisms include friction, fluid flow, viscous relaxation, and scattering. The application of these models to the ultrasonic data of ToksGz et al (1979, this issue) indicates that friction on thin cracks and grain boundaries is the dominant attenuation mechanism for consolidated rocks under most conditions in the earth' s upper crust. Increasing pressure decreases the number of cracks contributing to attenuation by friction, thus decreasing the attenuation. Water wetting of cracks and pores reduces the friction coefficient, facilitating sliding and thus increasing the attenuation. In saturated rocks, fluid flow plays a secondary role relative to friction. At ultrasonic frequencies in porous and permeable rocks, however, Biot-type flow may be important at moderately high pressures. "Squirting" type flow of pore fluids from cracks and thin pores to larger pores may be a viable mechanism for some rocks at lower frequencies. The extrapolation of ultrasonic data to seismic or sonic frequencies by theoretical models involves some assumptions, verification of which requires data at lower frequencies.

The province of Ontario (Canada) reported more laboratory confirmed rabid animals than any other state or province in Canada or the USA from 1958-91, with the exception of 1960-62. More than 95% of those cases occurred in the southern 10% of Ontario (approximately 100,000 km2), the region with the highest human population density and greatest agricultural activity. Rabies posed an expensive threat to human health and significant costs to the agricultural economy. The rabies variant originated in arctic foxes: the main vector in southern Ontario was the red fox (Vulpes vulpes), with lesser involvement of the striped skunk (Mephitis mephitis). The Ontario Ministry of Natural Resources began a 5 yr experiment in 1989 to eliminate terrestrial rabies from a approximately 30,000 km2 study area in the eastern end of southern Ontario. Baits containing oral rabies vaccine were dropped annually in the study area at a density of 20 baits/km2 from 1989-95. That continued 2 yr beyond the original 5 yr plan. The experiment was successful in eliminating the arctic fox variant of rabies from the whole area. In the 1980's, an average of 235 rabid foxes per year were reported in the study area. None have been reported since 1993. Cases of fox rabies in other species also disappeared. In 1995, the last bovine and companion animal cases were reported and in 1996 the last rabid skunk occurred. Only bat variants of rabies were present until 1999, when the raccoon variant entered from New York (USA). The success of this experiment led to an expansion of the program to all of southern Ontario in 1994. Persistence of terrestrial rabies, and ease of elimination, appeared to vary geographically, and probably over time. Ecological factors which enhance or reduce the long term survival of rabies in wild foxes are poorly understood.

Data indicated that oral rabies vaccination resulted in protective immunity in a sufficient percentage of the target wildlife population to preclude propagation of the disease and provided an effective means of controlling rabies in these species.

Animal rabies control has been frustrated by the existence of multiple wildlife reservoirs and the lack of efficacious oral vaccines. In this investigation, raccoons fed a vaccinia-rabies glycoprotein recombinant virus in a sponge bait developed rabies virus-neutralizing antibody (0.6-54.0 units) and resisted street rabies virus infection 28 and 205 days after feeding. Additional raccoons immunized by oral infusion with attenuated antigenic variants of rabies virus strains CVS-11 and ERA failed to develop rabies virus-neutralizing antibody. This work demonstrates the feasibility of a recombinant virus vaccine containing the rabies glycoprotein gene for immunization of raccoons, and possibly other wildlife, to obtain longterm protection against rabies.Annually, 25,000-30,000 humans in the U.S. are treated for possible rabies virus infection after exposure to known or suspected rabid animals. Infected wildlife constitute a significant reservoir of rabies virus for humans and domestic animals alike (1); therefore, a major aim toward control of sylvatic rabies has been to develop an efficacious, safe, and economical oral rabies vaccine suitable for effective field distribution. Initially, the red fox (Vulpes vulpes) was the predominant target for oral immunization (2-5), with protection demonstrated both in the laboratory and in European field trials. While these studies provided encouraging results, other species (e.g., the striped skunk Mephitis mephitis and the raccoon Procyon lotor), which are major rabies virus vectors within North America (6), have been refractory to efficient oral immunization against rabies (7). Due to a major rabies epizootic among raccoons in the mid-Atlantic region of the U.S. (8) (vol/vol) fetal calf serum] by oral infusion. Twenty raccoons were given 1.0 ml of undiluted V-RG virus in a 3-cm polyurethane sponge cube coated with paraffin and containing 100-200 mg of tetracycline HCl as a calciphilic biomarker (17); this sponge is under consideration as a vaccine field deployment bait (18). Thirteen control animals received a comparable volume of cell culture medium in a bait (sham immunization). A bait was placed in each cage, and after 48 hr untouched bait was removed. Any animal not eating a bait within this period was given 1.0 ml of either 108 or 106 pfu of V-RG virus by oral infusion, as described above. Blood was collected from all animals at the time of immunization and 16-28 days later. Rabies virus-neutralizing antibody levels were determined in vitro by a modification of the standard rapid fluorescent focus inhibition test (19, 20). Titers were expressed in units/ml using the National Institutes of Health reference serum (lot R-3) as standard.Virus Challenge and Post-Mortem Evaluation. V-RG virustreated and sham-immunized animals were challenged 28 or 205 days after immunization with 0.3 ml of rabies virus MD 5951 in the right dorsolateral aspect of the cervical musculature approximately 3.0 cm from the occipital junction. Animals were observed daily and were euthanat...

Static and dynamic bulk moduli (Ks and Kd) are measured as continuous functions of pressure from zero to 2‐3 kilobars for two sandstones, a tuff, limestone, granite, and oil shale. Results for the sandstones and granite are in good agreement with previously reported data with Ks/Kd varying from about 0.5 at atmospheric pressure to close to unity at pressures 2 kilobars and above. For rocks behaving elastically under static loading, the Ks/Kd ratio is inversely related to the microcrack density. For the limestone, time dependent deformation associated with pore collapse results in Ks/Kd ratios approaching 0.1 at high pressure. Upon unloading, while initially high ( ∼ 1.0) at high pressures, Ks/Kd becomes lower than values obtained during loading at low pressures ( < 1 kilobar) due to opening of microcracks generated during pore collapse. For the oil shale, in which few microcracks exist, Ks/Kd remains relatively constant with pressure at a value of about 0.7.

Ultrasonic P and S wave Q values as functions of hydrostatic pressure are presented for the Berea and Navajo sandstones, Bedford limestone, and Colorado oil shale. In most cases the attenuation was obtained for both dry and water‐saturated samples. Q is determined by measuring the attenuation of the rock sample relative to a high Q standard of identical geometry using Fourier spectral ratios. The data show that Q increases with pressure, the rate of increase being dependent on rock type and crack density and distribution. Qs is about equal to or larger than Qp for dry rocks and less than Qp for saturated rocks. In all cases, Q for saturated rocks are lower than for dry samples. The attenuation in the oil shale shows extreme anisotropy.

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