Site Characterization and Site Response Effects at CSMIP Stations: Tarzana and I-10 near La Cienega

9416424 Darragh这个项目的目的是增加对可能导致1994年加利福尼亚州北岭地震期间Tarzana的大震动和La Cienega附近的Santa Monica高速公路坍塌的场地影响的了解。Tarzana的预期结果将有助于类似地点的场地特征、地形放大和微区划分。I-10的预期结果将有助于场地描述以及类似场地的高速公路结构的设计和施工实践。结果将与桥梁设计师一起撕碎。这项研究的重点是加州强震仪器计划(CSMIP)两个站点的现场响应：Tarzana和Baldwin Hills(位于La Cienega的圣莫尼卡(I-10)高速公路坍塌附近)。这两个地点的目标是澄清：(1)通过采集和汇编地表和钻孔的地震、地质和岩土数据，不同地质情况对场地反应的影响；(2)场地利用特别关注的余震记录，在主震的强震记录中所作的贡献，是Tarzana记录到的持续和高幅度震动的原因，以及可能放大地震波并对La Cienega坍塌的I-10高速公路造成破坏的当地场地反应效应。采用了以下方法：1.通过标准的横波和纵波速度测量(地面和井下)和钻孔样品的岩土试验，从地表到基岩(或非常坚硬的材料)进行场地表征。2.对于距离和方位相近的台站，通过计算强震台和附近台址记录的余震的平滑几何平均傅立叶幅值谱的比值来估计场地反应，谱比法计算了来自震源和路径效应的场地反应。3.将一维线性模型、等效线性模型和二维非线性模型的场地响应预测与强震记录的实际响应进行比较，以识别场地效应，并将其与可能的震源和路径效应分开。***

9416424 Darragh The aim of this project is to increase the understanding of site effects that may have caused the large shaking at Tarzana and the Santa Monica Freeway collapse near La Cienega during the 1994 Northridge, CA earthquake. The anticipated results at Tarzana will be useful for site characterization, topographic amplification and microzonation at similar sites. The anticipated results at I-10 will be useful for site characterization as well as design and construction practices of freeway structures at similar sites. The results will be shred with bridge designers. The study focuses on the site response at two California Strong Motion Instrumentation Program (CSMIP) stations: Tarzana and Baldwin Hills (located near the Santa Monica (I-10)freeway collapse at La Cienega). The objectives at both sites are to clarify: (1) the effects of different geology on site response by the acquisition and compilation of seismic, geologic and geotechnical data at the surface and from drill holes; and (2) the contribution of the site in strong motion records of the mainshock by using aftershock recordings of particular interest are the causes of the sustained and high amplitude shaking of over 1 g that was recorded at Tarzana, and the local site response effects that may have amplified seismic waves and caused damage at the collapsed I-10 freeway at La Cienega. The following methods are employed: 1.Site characterization through standard shear-wave and compressional-wave velocity measurements (surface and downhole) and geotechnical testing of drillhole samples damping, density and modulus reduction) from surface to bedrock (or to very stiff material). 2.Site response is estimated by calculating the ratio of the smoothed geometric-mean Fourier amplitude spectra from aftershocks recorded at both the strong motion station and nearby sites For stations located at similar distances and azimuths from the earthquake, the spectral-ratio method is olates the site response from source and path effects. 3.Site response predictions from one-dimensional linear and equivalent-linear models and a two-dimensional nonlinear model are compared to actual response from strong motion recordings to identify site effects and separate them from possible source and path effects. ***