Severe Ground Motions

该项目的目标是提高工程师和科学家解决危及生命的最严重的地面运动的方法的准确性和有效性;这些运动被定义为可以引起高度非线性动力响应的运动，从而甚至破坏那些经过现代抗震设计的建筑物和结构。 目前的结构安全性测定方法受到无法预测地面震动达到这些破坏水平时的情况的限制。 基于一个有效的新的（结构相关的）标量测量地面运动的严重性，套件的真实的和现实的合成加速度记录的样本将被排名和最严重的深入研究，以了解为什么以及如何这些记录不同于更良性的识别。 定向感应脉冲可能是大断层附近某些结构的一种现象，这些结果将导致开发联合工程和地球科学工具的项目，用于评估剧烈运动的危害。 这些工具将包括一个新的概率地震危险性分析程序，该程序利用现代执业工程师对其特定结构的某些线性和非线性动态特性的知识，然后产生一个特定的威胁措施，更准确地预测结构受到这些罕见的，一个主要的项目产品是一个动态破裂模拟能力，它允许模拟大地震非常近场的地面运动。 由此，我们可以更好地了解控制震源各方面行为的因素，主要是上升时间，这些因素对控制严重地面运动的水平和特征非常重要。 我们的模型进行测试，相对于他们的能力，以产生样本的记录，准确地捕捉性能发现较早的结构产生严重的影响。 因此，该项目需要工程师和地球科学家之间不同寻常的互动。

The objectives of this project are to improve the accuracy and effectiveness of the way both engineers and scientists address the life-threatening, most severe ground motions; these are defined as those motions that can induce highly nonlinear dynamic response and hence damage even those building and structures that have undergone modern aseismic design. Current means of structural safety determination are limited by an inability to anticipate what the ground shaking will look like when it reaches these damaging levels. Based on an effective new (structure-dependent) scalar measure of ground motion severity, suites of real and samples of realistic synthetic accelerograms will be ranked and the most severe identified for study in depth to learn why and how these records differ from the more benign. Directivity-induced pulses can be one such phenomenon for certain structures at sites close to large faults.These results will lead to project development of joint engineering and earth science tools for the assessment of the hazard of severe motions. These tools will include a new probabilistic seismic hazard analysis procedure that takes advantage of the modern practicing engineer's knowledge of certain linear and nonlinear dynamic properties of his specific structure to then produce a particular measure of the threat that far more accurately predicts the demands on the structure when it is assaulted by these rare, severe ground motions.A major project product is a dynamic rupture modeling capability that allows simulations of ground motion in the very near field of large earthquakes. From this, we gain a better understanding of the factors that control behavior of aspects of the earthquake source, principally the rise time, that are important in controlling the level and character of severe ground motion. Our models are tested relative to their ability to produce samples of records that accurately capture the properties found earlier to produce severe effects in structures. Thus the project requires an unusual degree of interaction between engineering and earth scientists.