The Capital Digital Seismic Network,covering Beijing,Tianjin and central Hebei province,has recorded 1186 new earthquakes with M≥1.0 during May 2002 to Dec.2003,in which the arrival time differences between longitudinal wave and transverse wave are 2~25 s.
The result shows that before the M_S5.4 and M_S5.1 of Xiuyan earthquakes,the corner frequency ratio f_(cp)/f_(cs) of longitudinal wave and transverse wave all have obvious dropping anomaly before the 2 fairly large earthquakes. This anomaly will be the reference of future earthquake forecast and the basis of foreshock judgment.
He also predicted theoretically the pat-terns for producing three kinds of body waves in porous medium:fast longitudinal wave, slow longitudinal wave and transversal wave.
His wave equations may be changed into those in loose porous medium,where only fast longitudinal wave can be produced without slow longitudinal wave and transversal wave,thus leading to the same wave equation forms in compact medium and wet-grained loose medium.
The two cut-off points of these three stages are the preconsolidation stress and the structural yielding stress of the original clay, which could be determined by shear wave velocity measurement.
It is shown that in the presence of inhomogeneity the dispersion relation for the Tollmien-Schlichting waves is split into two branches periodic in the transverse wave number, which correspond to symmetric and antisymmetric modes.
Based on Boit's theory and the theory of elementary acoustic sources, the wave amplitude and radiation power are calculated for two kinds of longitudinal waves and the transverse wave.
It is obvious that in a plasma there can be no such bands, since bound states of a particle with a transverse wave whose phase velocity vph is higher than c are impossible in this case.
Analysis of our solutions and models indicates that the presence of a longitudinal acoustic wave leads not only to a change in the amplitude and phase of the transverse wave but also to a qualitatively new dynamics of sound in such a medium.
A new technique for testing long-range order in high-absorption anisotropic crystals has been developed using conversion of an incident p-(s-)wave to an s-(p-)wave due to optical anisotropy.
Secondly, on condition that transversal wave vector kx equaled ky, dispersion relations between longitudinal and transversal wave vectors were analyzed in detail.
The waveform trains gotten by laboratory simulation on acoustic logging with phased array transmitter was studied by the amplitude and frequency of the waveforms.The influential factors of delay time exerted on neighboring elements and element number were analyzed.The experimental results show that by increasing delay time exerted on neighboring elements,steered radiation angle of the phased array becomes larger and larger,and generation conditions of the refracted compressional wave and the refracted shear...