The Influence of Critical Reflections on Ground Motions Recorded in San Francisco and Oakland During the 1989 Loma Prieta Earthquake

该项目是NSF/USGS的一部分。 国家地震局的倡议 减少危害计划（NEHRP）， 调查洛马普列塔的影响 1989年10月17日地震。 在旧金山记录到的强烈的地面运动 洛马普列塔期间的弗朗西斯科湾区 地震超过了预测的水平， 标准经验衰减关系。 一 对这些记录的初步分析 表明这可能是 地震波临界反射 从地壳底部开始 本提案的目的是执行 进一步的分析和模拟使用一个 包括记录的扩展数据库 地震序列中的其他事件 为了严格测试这个和其他 对大地震的解释 观察 评估观察到的原因 偏离预计地面高度 这一运动对以下方面具有重要影响： 从未来大规模地震中估算地面运动 圣安德烈亚斯和海沃德地震 断层 它也对其他 美国的一些地区，如 西雅图-波特兰地区 震源深度较深的地震可能 类似地， 在遥远的地方， 西雅图、洛杉矶、湖城 流域响应影响的其他区域 预计将是重要的。

This project is part of the NSF/USGS initiative within the National Earthquake Hazard Reduction Program (NEHRP) to investigate the effects of the Loma Prieta earthquake of 17 October 1989. The strong ground motions recorded in the San Francisco Bay Area during the Loma Prieta earthquake exceeded the levels predicted by standard empirical attenuation relations. A preliminary analysis of these records suggests that this may have been a result of critical reflections of the seismic waves from the base of the crust. The objective of this proposal is to perform further analyses and simulations using an expanded data base that includes recordings of other events of the earthquake sequence in order to rigorously test this and other explanations for the large ground motions observed. Evaluating the cause of this observed departure from predicted levels of ground motion has important implications for estimating ground motions from future large earthquakes on the San Andreas and Hayward faults. It also has implications for other regions in the United States such as the Seattle-Portland region where crustal earthquakes having deep focal depths may similarly elevate ground motions to damaging levels at distant locations; and in the Seattle, Los Angeles, Salt Lake City and other regions where basin response effects are expected to be significant.