NEESR-CR: Topographic Effects in Strong Ground Motion - From Physical and Numerical Modeling to Design

该奖项是NSF 09-524项目招标“小乔治·e·布朗地震工程模拟（NEES）研究网络（NEESR）”竞赛的结果，包括华盛顿州立大学（牵头机构）、德雷塞尔大学（子奖项）、佐治亚理工学院（子奖项）、阿肯色大学（子奖项）和波多黎各大学（子奖项）。该项目将利用加州大学戴维斯分校和德克萨斯大学奥斯汀分校的NEES设备站点。地形效应是指在山腰、山脊、峡谷等地形特征附近对地震地面运动的改变和放大。这种有据可查的现象还没有在设计规范中得到解决。由于构造和地形密切相关，世界上大多数地震活跃地区都以显著的地形起伏为标志。近几十年来，人口增长和未开发大都市土地的稀缺改变了城市土地利用模式，并将越来越多的人口和基础设施资产置于地震期间易受地形影响的地区。虽然人们普遍认为地形放大会增加地震风险，但目前在如何可靠地量化其影响方面尚无共识。由于缺乏共识，无法就如何在实践中解释这一现象制定可接受的指导方针，因此在常规设计中没有考虑到造成地震危险的一个重要因素。到目前为止，理解和实际模拟地形效应的一个主要障碍是缺乏具有地形特征的密集仪器地点的统计显著数量的地震记录。此外，虽然现有的理论模型一般能够定性地预测不规则地形特征对地震地面运动的影响，但在预测和观测之间仍然存在显著的定量差异。本研究通过研究地表运动的地形放大来解决这个问题，该研究将包括一个综合的实验模拟、现场测量、经验数据分析和数值模拟程序。这些研究方法，在NEES的框架下一起应用，将迅速而实质性地推进对地形效应的理解。这种新的认识反过来又将允许开发数据和分析驱动的指导方针，以考虑工程设计、建筑规范规定、地震风险和微区划研究中的这些影响。知识价值：本研究整合了地形效应方面的知识，这些知识来自：(i)对地形特征进行离心模型测试（使用加州大学戴维斯分校的NEES岩土离心机）；（ii）用临时的、局部密集的仪器阵列获取现场数据（使用德克萨斯大学的NEES移动设备）；Austin和来自地震学联合研究机构（IRIS）大陆岩石圈阵列地震研究项目（PASSCAL）的宽带传感器记录了犹他州山区频繁和可预测的应力诱发采矿地震活动，（iii）严格的数值模拟研究，（iv）下一代衰减强地震动数据库的统计分析。预计这项工作将导致：(i)地形放大的高质量数据量的数量级增加，（ii）对这一现象的更深入的基本理解，（iii）地形对地面运动的影响的量化，（iv）改善了考虑地形放大的衰减关系，以及(v)在实践中广泛采用的指导方针和规定来解释这种地震危险。最终，这项研究的结果将使地震风险在地面运动量化和现场反应预测方面得到更有效的管理。更广泛的影响：该项目实施了一个新的通往博士学位的桥梁项目（BDP），旨在教育地震工程领域代表性不足的学生。BDP还可以作为增加大型科学、工程和技术合作研究项目多样性的模式。虽然这项研究的重点是与地震反应有关的问题，但基础知识将与其他危害相关，如自然地形中的山体滑坡和水坝、堤坝和堤防的稳定性。该项目的数据将存档，并通过NEES数据储存库向公众提供。

This award is an outcome of the NSF 09-524 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)" competition and includes Washington State University (lead institution), Drexel University (subaward), Georgia Institute of Technology (subaward), University of Arkansas (subaward), and University of Puerto Rico, Mayaguez (subaward). This project will utilize the NEES equipment sites at the University of California, Davis and the University at Texas, Austin. Topographic effects refer to the modification and amplification of seismic ground motion in the vicinity of topographic features such as hillsides, ridges, and canyons. This well-documented phenomenon has yet to be addressed in design codes. Because tectonics and topography are closely related, most seismically active regions of the world are marked by significant topographic relief. In recent decades, population growth and scarcity of undeveloped metropolitan land have changed urban land use patterns and placed an increasing number of people and infrastructure assets in areas susceptible to topographic effects during earthquakes. Although it is widely recognized that topographic amplification can elevate seismic risk, there is currently no consensus on how to reliably quantify its effects. Lack of consensus has precluded development of acceptable guidelines on how to account for this phenomenon in practice, thus leaving an important factor contributing to seismic hazard unaccounted for in routine design. Until now, a major impediment towards understanding and realistically modeling topographic effects has been the lack of a statistically significant number of seismic recordings from densely instrumented sites with topographic features. Moreover, while existing theoretical models are generally capable of qualitatively predicting the effects of irregular topographic features on seismic ground motion, there is still significant quantitative disagreement between predictions and observations. This research addresses this problem with a study of topographic amplification of ground motion that will include a comprehensive and integrated program of experimental simulations, field measurements, empirical data analysis, and numerical modeling. These research methods, applied together in a framework now made possible by NEES, will quickly and substantially advance the understanding of topographic effects. This new understanding will in turn permit the development of data- and analysis-driven guidelines to account for these effects in engineering design, building code provisions, and seismic risk and microzonation studies. Intellectual Merit: This research integrates knowledge about topographic effects gained from: (i) centrifuge model testing (using the NEES geotechnical centrifuge at the University of California, Davis) of topographic features, (ii) field data acquired with temporary, locally-dense instrumentation arrays (using the NEES mobile equipment at the University of Texas, Austin and broadband sensors from the Incorporated Research Institutions for Seismology (IRIS) Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL)) recording frequent and predictable stress-induced mining seismicity in a mountainous region of Utah, (iii) rigorous numerical modeling studies, and (iv) statistical analyses of the Next Generation Attenuation strong ground motion data base. It is envisioned that this work will result in: (i) an order-of-magnitude increase in the amount of high quality data on topographic amplification, (ii) greater fundamental understanding of this phenomenon, (iii) quantification of topographic effects on ground motions, (iv) improved attenuation relationships that account for topographic amplification, and (v) widely adopted guidelines and provisions to account for this seismic hazard in practice. Ultimately, the outcomes of this research will allow seismic risk to be more effectively managed in terms of ground motion quantification and site response prediction.Broader Impacts: This project implements a new Bridge to Doctorate Program (BDP) geared towards educating underrepresented students in the field of earthquake engineering. The BDP can also serve as a model for increasing diversity in large collaborative science, engineering and technology research projects. While this research focuses on issues related to seismic response, the fundamental knowledge will have relevance to other hazards, such as landslides in natural terrain and the stability of dams, levees, and embankments. Data from this project will be archived and made available to the public through the NEES data repository.