SPATIAL CHARACTERISTICS AND VISUAL EVALUATION OF STRONG GROUND MOTION ON 3-D SEDIMENTARY BASINS WITH THE AID OF PARALLEL COMPUTING

应用直接三维边界元方法计算了三维沉积盆地的地震响应，以估计1995年日本强震期间神户市重灾区地震动的放大特征。我们应用直接三维边界元方法计算了三维沉积盆地中的地震波，包括1)平面波、2)点震源和3)哈斯克尔型断层。我们将格林函数用于弹性半空间媒质。通过与其他方法计算结果的比较，验证了格林函数的准确性。首先，我们考虑了平面P波、SH波和SV波的入射。给出了这些速度结构的两层模型的面波基模的频散曲线。根据频域结果，我们使用FFT算法计算合成地震记录。这些反应清楚地表明…的传播沉积盆地边缘产生了更多的乐夫波。结果还表明，由于Love波和沉积盆地边缘产生的瑞利波向盆地中心传播，盆地中心被放大的幅度最大，虽然边缘附近的几个场地也有一定的放大，但放大的幅度仍比剩余场地小1.3倍左右。结果表明，体波即SH波首先到达场地，然后从盆地边缘产生的Love波沿纵向向前传播，从另一个盆地边缘反射向后传播。研究还发现，尽管体波随着震源-接收距离的增加而衰减，但乐夫波并没有衰减，因为假定盆地的材料性质是理想的弹性介质，介质界面倾角对地表响应的影响似乎很小。最后，我们计算了盆地对Haskell型断层源的地震运动。数值结果表明，盆地边缘某些限制区域的地震动放大程度最大，定性地验证了神户市重灾区地震动放大的特点。较少

A direct three-dimensional boundary element method is applied to evaluate seismic responses in three-dimensional sedimentary basin to estimate the amplification characteristics of the ground motions in the heavily damaged belt zone in Kobe City during the 1995 Hyogoken eathquake. We have applied a direct 3-D boundary element method to evaluate seismic waves in a 3-D sedimentary basin due to 1)plane waves, 2)point sources, and 3)Haskel type fault. We have utilized the Green's functions for an elastic half-space medium. The accuracy of the Green's functions was verified through comparison of the numerical results with those obtained by other methods.Firstly, we considered the incidence of plane waves of the P,SH,and SV waves. The dispersion curves of the fundamental modes of the surface waves for the two layred model of these velocity structures are, shown. From frequency domain results we computed synthetic seismograms using the FFT algorithm. Those responses clearly show propagation of … More Love waves generated from edge of the sedimentary basin. Thef also show that the center of the basin is most amplified since Love waves as well as Rayleigh waves generated from edge of the sedimentary basin propagate toward the center of the basin, and though several sites near the edge show some amplification, the magnitude of amplification remains to be less about 1.3 times than theremaining sites.Secondly, we calculated the seismic motion of the basin to a point source. It is seen that body waves, i.e., SH waves, first arrive at the sites and then Love waves generated from the basin edge propagate forward along the longitudinal direction and propagate backward reflected from the other basin edge. It is also seen that though the body waves decay with the increase of source-receiver distance, Love waves do not decay because the material property of the basin is assumed to be a perfect elastic medium.It seems that the effect of angle of inclination of medium interface on the surface responses is small.Finally, we calculated the seismic motion of the basin to a Haskell type fault source. Numerical results show that ground motions of some restricted area near basin edge are most amplified and that it is qualitatively verified that the amplification chariacterstics of the ground motions in the heavily damaged belt zone in Kobe city. Less