Deep Arrays for Earthquake Response, San Francisco Bay Area

这一行动是为了支持与美国地质调查局（USGS）合作，并可能与加州矿业和地质部门（CDMG）合作，在旧金山湾区安装两个深层阵列。目的是测量预计将在旧金山湾区发生的大地震期间的地面运动和地下水压力高程。这些记录将为地震学、地震工程和减轻地震危险的研究提供宝贵的数据：目前还没有这些数据。1989年10月17日加利福尼亚洛马·普里塔地震的地面测量表明，在深粘土地区，峰值水平地面加速度的表观放大比预期的要高100%或更多；然而，在土壤剖面中没有测量数据显示基岩和地表之间的放大是如何进行的。其他地区也没有这种类型的强震数据。旧金山湾区很有可能（30年内67%）发生比洛马·普里塔地震强度更大的地震；因此，它是建立深度加速度计阵列以提高预测能力的绝佳地点。正在对该地区的地点进行调查，并确定了几个有希望的地点。由来自美国和加拿大主要大学以及美国地质勘探局和CDMG的减轻地震危险方面的著名研究人员和管理人员组成的咨询小组将就场地及其仪器的一般要求提供咨询意见。以及对仪器的位置，以最大限度地利用所恢复的数据。小组成员具有地球科学、岩土工程和实地数据测量方面的专业知识。Loma Prieta地震以及世界范围内以往的大地震造成的破坏表明，需要测量两种不同类型的数据，以改进地震减灾方法：在强震引起的地面震动期间测量深层粘土沉积物中地面运动的放大；以及强震时饱和砂土中的地面运动和地下水压力的增加。这些测量结果可以通过两个单独的现场阵列获得，或者在具有饱和砂和深层粘土沉积的适当组合的地点进行组合阵列。设立这些阵列是遵照1988年9月关于“美国岩土工程试验指定场址”讲习班和1990年11月关于“动态土壤特性和场址特征”讲习班的建议。这些地点将成为指定的岩土试验地点，向所有感兴趣的研究人员开放。这些地点可用于研究与地震无关的岩土工程现象，但预期所选地点一般更适合调查所讨论的地震引起的现象。

This action is to support the installation, in collaboration with the U.S. Geological Survey (USGS) - and possible collaboration with the California Division of Mines and Geology (CDMG) - of two deep arrays in the San Francisco Bay area, with the objective of measuring ground motions and the elevation of ground water pressure during the large earthquake that is expected to occur in the San Francisco Bay area. These recordings will provide valuable data for seismological, earthquake engineering and earthquake hazard mitigation studies: these data do not exist at present. Surface measurements from the October 17, 1989 Loma Prieta, California earthquake showed that the apparent amplification of the peak horizontal ground acceleration at deep clay sites was higher by 100% or more than would have been anticipated; yet no measurements in the soil profile showing how amplification progressed between bedrock and the ground surface are available. Nor are data of this type available at other locations for strong-motion earthquakes. There is a significant probability (67% in 30 years) that an earthquake producing greater intensity of motion than the Loma Prieta event will occur in the San Francisco Bay area; it is thus an excellent location to establish a deep accelerometer array to improve prediction capabilities. Sites are being surveyed in the area, and several promising locations have been identified. An advisory panel consisting of eminent researchers and administrators in earthquake hazard mitigation, from major universities in the United States and Canada, and from the USGS and CDMG, will provide advice on the general requirements for the sites and their instrumentation, as well as on the location of instruments to maximize the usefulness of the data recovered. The panel members have expertise in earth science, geotechnical engineering, and field data measurements. The damage caused by the Loma Prieta earthquake, as well as previous major earthquakes worldwide, point to the need to measure two different types of data so as to improve earthquake hazard mitigation methods: The measurement during strong earthquake-induced ground shaking of the amplification of ground motions in deep clay deposits; and the ground motions and the increase in ground water pressure in saturated sands during strong earthquakes. These measurements could be obtained through two separate field arrays, or a combined array at a site which has the appropriate combination of saturated sands and deep clay deposits. The establishment of these arrays follows the recommendations of the September 1988 workshop on "Designated Sites for Geotechnical Experimentation in the United States", and the November 1990 workshop on "Dynamic Soil Properties and Site Characterization". These sites will become designated geotechnical test sites, open to all interested researchers. The sites will be available for research into geotechnical phenomena not associated with earthquakes, but it is expected that the sites chosen will, in general, be more suitable for investigation of the earthquake-induced phenomena discussed.