Ground Motion Prediction Under Uncertainty

这个项目的目标是预测由海沃德断层和圣安德烈亚斯断层上的假定地震引起的旧金山湾金银岛的强烈地面运动。近年来，各种工程师和地震学家组织开展了地震预测工作，例如对加利福尼亚州的土耳其平地(1990年)，日本的阿什加拉山谷(1992年)，以及最近的日本神户/大阪地区(1998年)。基本思想是尝试对测量的地面反应进行建模和/或预测尚未进行记录的地点的响应，从而允许对不同的预测方法进行比较。这些练习突显了该项目试图避免的几个困难，方法是将重点放在一个记录非常充分的地点-加利福尼亚州金银岛的国家岩土工程试验场-并要求对海沃德和圣安德烈亚斯断层的运动进行预测。美国地质调查局的研究人员最近汇编了旧金山湾区的地质数据，再加上加州交通部为新海湾大桥跨度进行的密集地质研究，极大地减少了路径不确定性问题。该项目包括两部分预测工作。在第一部分(本项目)，预报员将开发金银岛下的基岩运动谱，以预测两个断层上的地震情景。将在第一个资格预审阶段之后选择预测者，在这一阶段中将选择一系列方法。一旦对这一有充分记录的环境做出预测，不同方法中隐含的不确定性将更容易在最终研讨会上量化。来自不同大学的至少五个学生团队也将被邀请提出预测，将在最后的研讨会上讨论，并包括在会议记录中。计划在这项工作完成后进行第二阶段，在这一阶段中，预报员将获得岛下一致的基岩运动，并预测90米深软土剖面中不同点以及岛上其他点的土壤响应。这一第二阶段将是一个后续项目，旨在通过最先进的方法研究震源-路径-地点预测所涉及的最终累积不确定度。

The objective of this project is to predict the strong ground motions at Treasure Island, in San Francisco Bay, resulting from postulated earthquakes on the Hayward and the San Andreas faults.Earthquake prediction exercises have been carried by various organizations of engineers and seismologists in recent years; for example for Turkey Flat, California (1990), the Ashigara Valley, Japan (1992) and most recently for the Kobe/Osaka region in Japan (1998). The basic idea was to attempt to model measured ground response and/or to predict response for sites at which recordings had not been made, permitting different methods of prediction to be compared. These exercises highlighted several difficulties that this project will attempt to avoid by focusing on one very well documented site - the National Geotechnical Experimentation Site at Treasure Island, California - and asking for predictions of motion on the Hayward and the San Andreas faults. A recent compilation of geologic data for the San Francisco Bay Area by researchers at the United State Geological Survey, combined with the intensive geologic studies by CALTRANS (California department of transportation) for the new Bay Bridge span have drastically reduced path uncertainty problems.The project involves a two-part prediction exercise. In the first part (this project), predictors will develop bedrock motion spectra under Treasure Island, for scenario earthquakes on the two faults. Predictors will be selected after a first pre-qualification phase, in which a selection of a range of approaches will be made. Once predictions for this well-documented setting are made, uncertainties implicit in the different methods will be easier to quantify at a final workshop. At least five student teams from different universities will be invited to present predictions as well, to be discussed at the final workshop, and included in the proceedings. A second phase is planned once this work is completed, in which predictors would then take the consensus bedrock motions under the island and predict soil response at various points in the 90-meter-deep soft soil profile, as well as at other points on the island. This second phase will be a follow-on project, intended to study the final cumulative uncertainties involved in source-path-site predictions by state-of-the art methods.