浅、深冲积盆地的地震场地效应：深部运动与聚焦效应
Seismic Site Effects for Shallow and Deep Alluvial Basins: In-Depth Motion and Focusing Effect
摘要：
本文的主要目的是分析各种冲积盆地的地震场地效应。考虑数值方法（边界元法）进行分析。两个主要的情况被认为是：在尼斯（法国）[1]和加拉加斯（委内瑞拉）[2]深不规则盆地中心的浅沉积。本文从水平、发生频率和位置三个方面分析了地震动放大作用。对于这两个网站，放大因子被发现达到最大值20（弱运动）。然而，场地效应在频率依赖性和最大放大率的位置方面具有非常不同的特征。对于Nice的浅层沉积物，低频放大因子非常小，并且在1.0 Hz以上快速增加。不规则的加拉加斯盆地给出了不同的频率依赖性，在不同的频率有许多不同的峰。加拉加斯深冲积盆地的模型还包括当地地形的一部分，如最近的山脉。人们可以估计地震现场的影响，由于速度对比（盆地和基岩之间）和当地地形的网站。此外，最大的放大位于尼斯的表面上，而一些强放大区也出现在加拉加斯的情况下，盆地本身。一个调查的影响，这种聚焦效果的运动与深度的依赖性。这对地下结构的地震反应分析具有重要意义。冲积层的形式和深度，然后发现有很大的影响，在表面上的最大放大的位置，但也在深不规则盆地的存款。这对于地表和地下结构的地震反应分析是必不可少的。
英文摘要：
The main purpose of the paper is the analysis of seismic site effects in various alluvial basins. The analysis is performed considering a numerical approach (Boundary Element Method). Two main cases are considered : a shallow deposit in the centre of Nice (France) [1] and a deep irregular basin in Caracas (Venezuela) [2]. The amplification of seismic motion is analysed in terms of level, occuring frequency and location. For both sites, the amplification factor is found to reach maximum values of 20 (weak motion). Site effects nevertheless have very different features concerning the frequency dependence and the location of maximum amplification. For the shallow deposit in Nice, the amplification factor is very small for low frequencies and fastly increases above 1.0 Hz. The irregular Caracas basin gives a much different frequency dependence with many different peaks at various frequencies. The model for Caracas deep alluvial basin also includes a part of the local topography such as the nearest mountain. One can estimate seismic site effects due to both velocity contrast (between the basin and the bedrock) and local topography of the site. Furthermore, the maximum amplification is located on the surface for Nice, whereas some strong amplification areas also appear inside the basin itself in the case of Caracas. One investigates the influence of this focusing effect on the motion vs depth dependence. This is of great interest for the analysis of seismic response of underground structures. The form and the depth of alluvial deposits are then found to have a great influence on the location of maximum amplification on the surface but also inside the deposit for deep irregular basins. It is essential for the analysis of the seismic response of both surface and underground structures.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
