Nondestructive Characterization of Liquefaction Features Using Ground Penetrating Radar

9412666里克斯1994年1月17日北岭地震（M=6.6）导致圣费尔南多谷，西米谷和雷东多海滩地区的地表塌陷。 特别令人感兴趣的是在下圣费尔南多大坝上游的废弃水库（“碎屑盆地”）中观察到的液化特征（砂沸和地裂缝）。 在大坝附近的加州强运动仪器计划（CSMIP）观测站，观测到自由场加速度高达0.90 g（水平）和0.60 g（垂直）。 虽然砂沸和裂缝提供了宝贵的液化地表证据，但它们几乎没有揭示液化的地下性质。 本项目使用探地雷达（GPR）试验对观测到的液化特征进行非破坏性成像。 探地雷达使用电磁波对地下进行成像，从而得到类似于地震反射截面的现场地层表示。 目的是沿沿着几条线进行GPR测试，以成像表面沿着的横向扩展发展，并沿沿着几个紧密间隔的线，以产生一个三维图像的砂沸。 预计这些液化特征的详细地下图像将有助于规划随后的现场调查。 该项目使用全球定位系统（GPS）接收器来测量探地雷达测量区域的地形。 这些全球定位系统的测量结果使雷达数据能够根据地形影响进行校正。 ***

9412666 Rix The January 17, 1994 Northridge Earthquake (M=6.6) caused liquefaction-induced ground failures in the San Fernando valley, Simi valley, and Redondo Beach areas. Of particular interest were the liquefaction features (sand boils and ground fissures) observed in the abandoned reservoir ("debris basin") upstream of the Lower San Fernando Dam. Free-field accelerations as large as 0.90 g (horizontal) and 0.60 g (vertical) were observed at California Strong Motion Instrumentation Program (CSMIP) stations in the vicinity of the dam. Although sand boils and fissures offer valuable surface evidence of liquefaction, they reveal little about the subsurface nature of the liquefaction. This project uses ground penetrating radar (GPR) tests to image the observed liquefaction features nondestructively. GPR uses electromagnetic waves to image the subsurface, resulting in a representation of the site stratigraphy that is similar to a seismic reflection cross section. The objective is to perform GPR tests along several lines to image the surface along which lateral spreads developed, and along several closely spaced lines to generate a three-dimensional image of a sand boil. It is anticipated that detailed subsurface images of these liquefaction features will be useful in planning subsequent site investigations. The project uses a global positioning system (GPS) receiver to measure the topography of the area of the ground penetrating radar measurements. These GPS measurements allow the radar data to be corrected for topographic effects. ***