Improved Liquefaction Hazard Mapping Procedures for Urban Areas

在美国和日本的许多大地震中，液化对城市地区造成了广泛的破坏和破坏。 这种破坏引起了公众对州和地方政府、公用事业以及其他负责机构和公司的需求，以减轻各自管辖范围内的液化危害。 减轻灾害的第一步是通过液化危害图确定脆弱地区和潜在有害影响。 大多数美国液化危害图是基于地质单位的广义标准，导致定性危害等级高，中，低等用户，包括城市规划师，建筑官员，工程师，公用事业公司，和损失估计，需要更多的细节和准确性比那些基于广义地质标准的地图。 本研究的目的是开发出更好的液化危险性绘图技术，以满足这一需求。 编制这种地图需要根据详细的地下地层和土壤特性进行评价。 为了开发和测试改进的技术，需要一个测试区，在那里已经汇编了大量的钻孔或CPT日志和附带的土壤特性数据，并且已经记录了过去地震的液化和随之而来的有害影响。 日本科比大学Yasuo Tanaka教授及其同事为日本大都市区科比编制了大量岩土工程数据，这是开发和测试制图技术的一个独特机会。 该数据集包括分布在科比和两个邻近社区的5，000多个钻孔日志，日志集中在1995年兵库县南部（科比）地震严重受损的地区。 同样，包括东京早稻田大学的Masanori Hamada教授及其同事在内的日本研究人员也对所观察到的液化效应（包括横向扩展位移）进行了广泛汇编。 该项目的目标是与田中教授及其同事共同开发改进的敏感性和地面故障危险绘图程序。 这些技术将通过分析科比地区的地下沉积物地层、土壤特性、当地地形和过去的液化效应来开发。 根据这些分析，将制定和评价几种可能的程序，以绘制可液化层和随之产生的危险。 最可行的技术或技术，然后将用于准备示范液化危险地图的选定部分的科比大都市区和城市地区在美国。 一个可能的城市地区为美国示范地图是奥克兰，加州，市区博士托马斯L。美国地质勘探局的霍尔泽公司正在安装大量的CPT测深和SPT钻孔，并从这些钻孔收集数据。 霍尔泽博士的工作专门针对液化危害的评估。

Liquefaction has generated widespread damage and disruption to urban areas during many large US and Japanese earthquakes. This destruction has created public demand for state and local governments, public utilities, and other responsible agencies and corporations to mitigate liquefaction hazard in their respective jurisdictions. An initial step in hazard mitigation is definition of vulnerable areas and potential deleterious effects through liquefaction hazard maps. Most US liquefaction hazard maps are based on geologic units with generalized criteria leading to qualitative hazard ratings of high, moderate, low, etc. Users, including city planners, building officials, engineers, utility companies, and loss estimators, need maps with more detail and accuracy than those based on generalized geologic criteria. The purpose of this study is to develop improved mapping techniques for delineation of liquefaction hazard to meet this need. The compilation of such maps will require evaluations based on detailed subsurface stratigraphy and soil properties. To develop and test improved techniques, a test area is needed where an extensive array of borehole or CPT logs and accompanying soil property data has been compiled and where liquefaction and consequent deleterious effects from a past earthquake have been documented. A unique opportunity to develop and test mapping techniques has occurred with the compilation of a large set of geotechnical data for the Kobe, Japan metropolitan area by Prof. Yasuo Tanaka and his colleagues at Kobe, Japan, University. This data set consists of over 5,000 borehole logs scattered over Kobe and two adjacent communities, with concentrations of logs in areas heavily damaged by the 1995 Hyogoken-Nanbu (Kobe) earthquake. Similarly, an extensive compilation of observed liquefaction effects, including lateral spread displacements, has been assembled by Japanese investigators, including Prof. Masanori Hamada and his colleagues at Waseda University, Tokyo. The objective of this project is to work jointly with Prof. Tanaka and his colleagues to develop improved susceptibility and ground failure hazard mapping procedures. These techniques will be developed by analyzing subsurface sediment stratigraphy, soil properties, local topography, and past liquefaction effects in the Kobe area. From these analyses, several possible procedures will be developed and evaluated for mapping liquefiable layers and consequent hazards. The most viable technique or techniques will then be used to prepare demonstration liquefaction hazard maps for selected parts of the Kobe metropolitan area and an urban area in the US. A likely urban area for the US demonstration map is Oakland, California, urban area where Dr. Thomas L. Holzer, USGS, is in the process of installing and collecting data from a large array of CPT soundings and SPT boreholes. The work of Dr. Holzer specifically directed toward evaluation of liquefaction hazard.