An in situ experimental study of variations of compressional wave speed and attenuation with depth in natural coral sands has been made offshore of Oahu, Hawaii. In situ data were collected at a center frequency of 7.5 kHz. Compressional wave speed averages around 1620 m/s and attenuation ~expressed as Qp , the reciprocal of the quality factor! decreases from 0.04 at the seafloor to 0.01 at 2 m...

I present a frequency-independent 3D seismic attenuation model (indicated by Q−1 P ) for the crust of the Salton trough and the adjacent regions in southeastern southern California. The simul2000 tomographic algorithm was used to invert the frequency-independent attenuation operator t values measured from amplitude spectra of 23,378 P-wave arrivals of 1203 events through a recently developed 3D...

earthquakes travel times inversion for determination of velocity structure of crust is one of the most important objectives in seismology. in the simultaneous inversion method, the parameters of earthquakes and velocity model are determined initially and are improved during inversion steps. in this study, we have used more than 22000 calculated travel times for first arrivals of 6000 earthquake...

accurate measurements of physical characteristics of bone are essential for diagnosis, assessment of change following treatment, and therefore, indirectly, for evaluation of new forms of therapy. this is particularly true of osteoporosis and aging skeleton, in which fractures occur easily. methods: in this study an ultrasonic system was set-up and calibrated on plexiglas tubes of variable thick...

The monitoring of both linear and nonlinear elastic properties of a high performance concrete during curing is presented by application of compressional and shear waves. To follow the linear elastic behavior, both compressional and shear waves are used in wide band pulse echo mode. Through the value of the complex reflection coefficient between the cell material (Lucite) and the concrete within...

A method for measuring in situ compressional wave attenuation exploiting the spectral decay of reflection coefficient Bragg resonances is applied to fine-grained sediments New England Mud Patch. Measurements layer-averaged a 10.3 m mud layer yield 0.04 {0.03, 0.055} dB/m/kHz (braces indicate outer bounds); twice as large at site with 3.2 thickness. It shown that both results are heavily influen...

Geophysical down-hole surveys can be used to measure the small strain dynamic properties of soils by the effects these properties have on wave propagation. The relevant effects include amplitude decay (corrected for beam divergence) and velocity dispersion. In this paper, down-hole data collected during the GeoInstitute's Denver 2000 field day are presented and analyzed as a Kelvin-Voigt solid....

Previous work from our laboratory showed that the widely reported decrease in phase velocity with frequency (negative dispersion) for ultrasonic waves propagating through trabecular bone can arise from the interference of two compressional waves, each of which exhibits a positive dispersion. Previous simulations suggest that Bayesian probability theory can be employed to recover the material pr...