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

应用三维边界元直接法计算三维沉积盆地中的地震反应，研究了1995年兵库县大地震时科比市严重破坏带的地震动放大特性。本文应用直接三维边界元法计算了平面波、点源和Haskel型断层引起的三维沉积盆地中的地震波。本文利用弹性半空间介质的绿色函数。通过与其它方法计算结果的比较，验证了绿色函数的准确性。首先，我们考虑了P波、SH波和SV波的平面波入射。文中给出了这些速度结构的两层模型的面波基模频散曲线。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， ...更多信息 勒夫波产生于沉积盆地边缘。由于Love波和Rayleigh波从沉积盆地边缘向盆地中心传播，盆地中心放大最大，虽然在盆地边缘附近的几个地点有放大现象，但放大幅度仍小于其它地点的1.3倍左右。可以看出，体波，即，SH波首先到达场地，然后从盆地边缘产生的Love波沿纵向沿着向前传播，并从另一盆地边缘反射后向传播。同时还发现，虽然体波随震源-接收器距离的增加而衰减，但由于盆地的物质性质被假定为理想弹性介质，Love波不衰减，介质界面倾角对地表响应的影响似乎很小.最后，计算了Haskell型断层震源作用下盆地的地震运动.数值结果表明，在盆地边缘附近的某些限制区，地震动放大作用最大，定性地验证了科比市重灾带地震动放大特性。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