Engineering geologic and geotechnical analysis of paleoseismic shaking using liquefaction effects: field examples
Engineering geologic and geotechnical analysis of paleoseismic shaking using liquefaction effects: field examples
复制标题
利用液化效应对古地震震动进行工程地质和岩土分析：现场实例
DOI：
10.1016/j.enggeo.2004.07.026
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发表时间：
2005
影响因子：
7.4
通讯作者：
S. Olson
中科院分区：
文献类型：
--
作者：
R. Green;S. F. Obermeier;S. Olson
从古液化研究中反算的地面运动特征被广泛接受的最大障碍通常源于三个不确定性：（1）液化后沉积物的岩土性质变化的重要性（例如，（2）从各个古液化场地选择合适的岩土工程土壤指标;（3）将各个古液化场地的震动强度反算结果整合到古地震震动强度区域评估中的方法。本文介绍了两个案例研究，说明了奥尔森等人概述的方法。[工程地质学，这个问题]，以解决这些不确定性。第一个案例研究是对田纳西州孟菲斯附近的一个场地进行的，其中使用了来自并排位置（一个液化位置和另一个无液化位置）的静力锥贯入试验数据，以便很容易地辨别液化后“老化”和密度变化对现场测量的土壤指数的影响是最小的。在第二个案例研究中，12个地点是在分散的位置在瓦巴什山谷和表现出古液化功能进行了分析。这些特征首先暂时归因于万森纳地震，发生在6100年BP左右，并用于说明我们提出的方法，选择有代表性的液化沉积物的土壤指数。这些指数用于反算各个地点的震动强度，然后将反算结果纳入万森纳地震矩震级M的区域评估。区域评估验证了临时假设，即分散地点的古液化特征主要是由万森纳地震引起的，该地震被确定为M = 7.5。详细讨论了评估中使用的不确定性和假设。
The greatest impediments to the widespread acceptance of back-calculated ground motion characteristics from paleoliquefaction studies typically stem from three uncertainties: (1) the significance of changes in the geotechnical properties of post-liquefied sediments (e.g., “aging” and density changes), (2) the selection of appropriate geotechnical soil indices from individual paleoliquefaction sites, and (3) the methodology for integration of back-calculated results of strength of shaking from individual paleoliquefaction sites into a regional assessment of paleoseismic strength of shaking. Presented herein are two case studies that illustrate the methods outlined by Olson et al. [Engineering Geology, this issue] for addressing these uncertainties. The first case study is for a site near Memphis, Tennessee, wherein cone penetration test data from side-by-side locations, one of liquefaction and the other of no liquefaction, are used to readily discern that the influence of post-liquefaction “aging” and density changes on the measured in situ soil indices is minimal. In the second case study, 12 sites that are at scattered locations in the Wabash Valley and that exhibit paleoliquefaction features are analyzed. The features are first provisionally attributed to the Vincennes Earthquake, which occurred around 6100 years BP, and are used to illustrate our proposed approach for selecting representative soil indices of the liquefied sediments. These indices are used in back-calculating the strength of shaking at the individual sites, the results from which are then incorporated into a regional assessment of the moment magnitude, M, of the Vincennes Earthquake. The regional assessment validated the provisional assumption that the paleoliquefaction features at the scattered sites were induced by the Vincennes Earthquake, in the main, which was determined to have M∼7.5. The uncertainties and assumptions used in the assessment are discussed in detail.