recordings of ambient noise or microtremors are increasingly used to find valuable information on soil in one dimension at a given site. ambient vibrations, which are assumed to be mainly composed of surface waves, can be used to determine the surface wave dispersion curve in order to retrieve shear wave velocity profile. in this regard, microtremors are usually recorded simultaneously in an ar...

doppler ultrasound can provide important information about vascular problems through the analysis of blood flow wave-form. the purpose of this study was obtaining the normal images of color doppler and estimation of blood flow velocity parameters of femoral artery in rabbits. left and right femoral arteries of 8 healthy adult new zealand rabbits were evaluated. color and spectral doppler images...

One way of developing a wave-equation approach to seismic imaging is based on the concept of downward continuation of the surface reflection data. Seismic imaging is typically based on the single scattering approximation, and assumes the knowledge of a, smooth, background model in which the mentioned downward continuation is carried out. The downward continued data are subjected, at each depth,...

Estimating an accurate velocity model is crucial for seismic imaging to obtain a good understanding of the subsurface structure. The objective of this thesis is to investigate methods of velocity analysis by optimizing seismic images. A conventional seismic image is obtained by zero-lag crosscorrelation of wavefields extrapolated from a source wavelet and recorded data on the surface using a ve...

Estimating an accurate velocity model is crucial for seismic imaging to obtain a good understanding of the subsurface structure. The objective of this thesis is to investigate methods of velocity analysis by optimizing seismic images. A conventional seismic image is obtained by zero-lag crosscorrelation of wavefields extrapolated from a source wavelet and recorded data on the surface using a ve...

To establish a versatile means for screening and management of nonalcoholic steatohepatitis (NASH), shear wave velocity was measured in 20 normal controls and 138 consecutive nonalcoholic fatty liver disease (NAFLD) cases. Referencing biochemical properties in 679 healthy volunteers, a formula to distinguish NASH suspects was established and validated in another cohort of 138 histologically pro...

S U M M A R Y To simulate seismic wave propagation in the spherical Earth, the Earth’s curvature has to be taken into account. This can be done by solving the seismic wave equation in spherical coordinates by numerical methods. In this paper, we use an optimized, collocated-grid finitedifference scheme to solve the anisotropic velocity–stress equation in spherical coordinates. To increase the e...

S U M M A R Y We demonstrate that the distribution of seismic noise sources affects the accuracy of Green’s function estimates and therefore isotropic and anisotropic tomographic inversions for both velocity and attenuation. We compare three methods for estimating seismic noise source distributions and quantify the potential error in phase velocity, azimuthal anisotropy and attenuation estimate...

Teleseismic tomography across the Chinese Tien Shan shows that seismic wave speeds in the lithosphere beneath central Tien Shan are high and therefore the lithosphere is not weaker than that beneath the adjacent undeformed Tarim and Junggar basins. There is evidence for significant velocity contrasts within the lithosphere that are presumably inherited from the Palaeozoic collision history. The...