Ground Response and Damage Intensity Correlations in Damage Zones on Basin Fringes

9416378罗林斯1994年北岭地震后，对圣费尔南多和洛杉矶盆地的破坏分布进行了初步审查，结果表明，破坏集中在盆地边缘的低层结构中，那里的土壤剖面相对较硬且较浅。 位于山谷边缘冲积层上的重力仪也表现出异常高的加速度，特别是在圣费尔南多附近。 与1985年墨西哥地震相比，由于靠近震源，传入的岩石运动似乎富含短周期能量，导致位于盆地边缘的较硬浅层沉积物（自然振动周期较短）显着放大。 预计短周期能量的放大将导致对位于这些沉积物上的短周期结构（如单层结构）的集中破坏。 也有可能是二维或三维盆地形状效应在这些位置的放大中发挥了作用。 该项目的目标是： (1)评估广泛使用的计算机代码（如SHAKE和DESRA）与记录的运动相匹配的能力，特别是在破坏强度相对较高的区域。 这些地面响应技术已被证明是有用的，在深软土网站，如在墨西哥城和旧金山弗朗西斯科，但还没有得到验证，对现场数据的硬浅网站。 其他地震活跃地区，如作为盐湖山谷，邻近山前有坚硬的浅层土壤，因此，校准这些场地条件的方法非常重要。 (2)标定Seed和Sun（1989）定义的损伤潜势指数（DPI）与结构损伤观测值之间的相关性。 在1967年委内瑞拉加拉加斯地震和1985年墨西哥地震后，观察到DPI和破坏强度之间的有用相关性。 然而，北岭地震提供了一个最好的机会，可以根据美国的情况来校准相关性。

9416378 Rollins A preliminary review of damage distribution in the San Fernando and Los Angeles basins following the 1994 Northridge earthquake indicates that damage was concentrated in low-rise structures at the fringes of the basins where soil profiles are relatively stiff and shallow. Accelerograms located on alluvium at the fringes of the valleys also exhibited unusually high accelerations, particularly in the vicinity of San Fernando. In contrast to the 1985 Mexico Earthquake, it appears that incoming rock motions were rich in short period energy due to the proximity to the source, causing significant amplification in the stiffer shallow deposits (with shorter natural periods of vibration) located at the fringes of the basins. Amplification of short period energy would be expected to result in a concentration of damage to short period structures (such as single story structures) located on these deposits. It is also possible that 2- or 3-D basin- shape effects played a role in the amplification at these locations. The objectives of this project are: (1) To evaluate the ability of widely used computer codes such as SHAKE and DESRA to match recorded motions, particularly in areas where damage intensity was relatively high. These ground response techniques have proven useful at deep soft soil sites such as those in Mexico City and San Francisco, but have not been verified against field data for stiff shallow sites. Other siesmically active areas, such as Salt Lake valley, have stiff shallow soils adjacent to mountain fronts and it is important to calibrate the methods for these site conditions. (2) To calibrate correlations between the damage potential index (DPI) defined by Seed and Sun (1989),and observed damage to structures. Useful correlations between DPI and damage intensity were observed following the 1967 Caracas, Venezuela earthquake and the 1985 Mexico Earthquake. However, the Northridge earthquake provides the best opportunity to d ate to calibrate the correlation for conditions in the U.S. ***