S U M M A R Y The differential attenuation for upper-mantle paths beneath northern Australia has been estimated using spectral ratio methods, both in a narrow frequency band near 0.6 Hz to obtain stable estimates for subsequent inversion and also over a broad frequency band up to 3–6 Hz to look at the frequency dependence of attenuation. The frequency dependence of the differential attenuation ...

stress waves contain useful information about the properties of porous materials; they can be recovered through different non-destructive testing methods such as crosswell, vertical seismic profile, borehole logging as well as sonic tests. in all these methods, it is crucial to assess the effects of frequency on wave attributes including velocity and intrinsic attenuation. the dependency of per...

introduction: photon attenuation in tissues is the primary physical degrading factor limiting both visual qualitative interpretation and quantitative analysis capabilities of reconstructed single photon emission computed tomography (spect) images. the aim of present study was to investigate the effect of attenuation correction on the detection of activation foci following statistical analysis w...

objective(s): in spect, the sinogram contains scatter and lack of attenuated counts that degrade the reconstructed image quality and quantity. many techniques for attenuation and scatter correction have been proposed. an acceptable method of correction is to incorporate effects into an iterative statistical reconstruction. here, we propose new maximum likelihood expectation maximization (mlem) ...

the strong ground motions recorded during the 2002 avaj earthquake have been used to estimates wave attenuation, qβ, and spectral decay parameter, κ, for the avaj region. qβ for shear wave is estimatedas a function of frequency in the range of 0.6- 18 hz. the results show that qβ increases with frequency in theform of qβ=62.7 f 0.9. our estimates are within the estimated range for different par...

a considerable amount of energy is released in the form of shock wave from explosive charge detonation. shock wave energy is responsible for the creation of crushing and fracture zone around the blast hole. the rest of the shock wave energy is transferred to rock mass as ground vibration. ground vibration is conveyed to the adjacent structures by body and surface waves. geological structures li...