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

9416378罗林斯对1994年北岭地震后圣费尔南多和洛杉矶盆地的破坏分布进行的初步审查表明，破坏集中在盆地边缘的低层结构，那里的土壤剖面相对坚硬和浅。位于山谷边缘冲积层上的加速图也显示出异常高的加速度，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，新来的岩石运动似乎具有丰富的短期能量，导致位于盆地边缘的较硬的浅层沉积(具有较短的自然振动周期)显著放大。短周期能量的放大预计将导致位于这些矿床上的短周期结构(如单层结构)的损害集中。也有可能是2-D或3-D盆地形状效应在这些位置的放大中起了作用。这个项目的目标是：(1)评估广泛使用的计算机代码，如SHAKE和DESRA，匹配记录的运动的能力，特别是在破坏强度相对较高的地区。这些地面响应技术在墨西哥城和旧金山等深厚软土场地被证明是有用的，但尚未与硬浅层场地的现场数据进行验证。其他地震活跃地区，如盐湖谷，山前附近有坚硬的浅层土壤，因此针对这些场地条件校准方法是很重要的。(2)标定Seed和Sun(1989)定义的损伤潜力指数(DPI)与结构损伤观测值之间的相关性。1967年委内瑞拉加拉加斯地震和1985年墨西哥地震后，DPI与破坏强度之间存在有用的相关性。然而，北岭地震提供了最好的机会来校准与美国条件的相关性。*

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. ***