抄録
As a special case of a relaxation source, a theoretical study is made of the seismic wave radiation from the sudden formation of a spherical fluid region in an infinite elastic medium subjected to pre-existing shear stress. The results are discussed in comparison with those for a spherical void cavity model in the same initial stress field. Almost or exactly identical results be-tween the present liquefaction model and the cavity model are found for (1) the spectral density of zero frequency limit at a large distance, Which coincides also with the displacement amplitude expected for an equivalent double-couple point source, (2) the ratio of P wave to S wave corner fre-quency, which is approximately equal to the velocity ratio of P waves to S waves, and (3) the total wave energy. Differences between the two models appear in (1) the predominant period of the displacement spectrum, (2) waveform of P waves in particular, and (3) the energy ratio of S waves to P waves (6.8 for the liquefaction model and 4.7 for the cavity model).
