Collaborative Research: 3-D Near-field Coseismic Deformation from Differential LiDAR with Application to the El Mayor-Cucapah Earthquake

断层带激光雷达扫描最强大的应用之一是作为断层前图像，与未来地表破裂地震后获得的调查结果进行比较。然后，每个位移特征都作为大地测量标记，由此可以构建地表位移场的超高分辨率地图。如此详细的位移场显示了断层及其包含的岩石体积如何在连续的地震中共同作用以适应变形和生长地质结构。这为地震破裂如何连接断层以产生更大、更具破坏性的事件提供了新的理解，并阐明了改善长期变形率和地震危险性估计所需的隐式分布变形成分。该项目由美国国家科学基金会EarthScope项目和美国国家科学基金会国际科学与工程办公室的美洲项目资助，支持开发全三维方法，通过连续的机载激光雷达扫描断层带来揭示变形。该项目的重点是2010年4月4日墨西哥下加利福尼亚州北部El Mayor-Cucapah （EMC）地震破裂前后的机载激光雷达扫描。该项目的目标是解决使用该数据集的三个挑战：(1)对震前数据进行再处理，以减少扫描伪影并提高精度；(2)从分辨率差异很大的点云数据（震后为9 ~ 18 pts/m2，震前为0.013 pts/m2）开发严格的高分辨率位移测量方法；(3)该事件断裂带变形的初步三维力学模拟。应对这些挑战将有助于我们进一步了解这次地震中断层带的变形情况，同时也有助于我们进一步利用差分激光雷达对下一次地震进行分析。差分激光雷达很可能沿着地球观测设备拍摄的众多活动断层中的某一条进行地震分析。同震地表破裂是一种重要的、可获得的地震滑动记录，也是史前地震活动的主要记录。差分激光雷达的近场变形测量可以改变我们对同震地表破裂是如何产生和分布在断裂带内的理解。要获得的新知识包括了解断层滑动与近场分布变形的机械耦合，量化断层滑动的分布成分，否则难以测量，并预测断层带周围可能破坏建筑物和关键基础设施的高应变的样式、程度和大小。为这个项目开发的技术也将被证明对其他应用有价值，如地貌学、土木工程和机器人技术。这项研究汇集了美国五个研究小组的专业知识，他们是差分机载激光雷达研究的领导者：加州大学戴维斯分校、亚利桑那州立大学、加州大学圣地亚哥分校、休斯顿大学和加州理工学院/美国地质勘探局。该项目还扩大了EMC地震后形成的国际合作，涉及来自下加利福尼亚州CICESE的研究人员和学生，共同开发和部署新的差分激光雷达算法和开源激光雷达可视化软件。

One of the most powerful applications of fault-zone LiDAR scans is to serve as the before image for comparison with a survey acquired after a future surface-rupturing earthquake. Then, every displaced feature acts as a geodetic marker from which an ultra-high resolution map of the surface displacement field may be constructed. Such a detailed displacement field shows how faults and their containing rock volume act together to accommodate deformation and grow geologic structures over successive earthquakes. This provides new understanding of how earthquake ruptures connect faults to generate larger, more destructive events, and illuminates cryptic, distributed components of deformation needed for improving estimates of long-term deformation rates and seismic hazard. This grant through the NSF EarthScope Program and the Americas Program of the NSF Office of International Science and Engineering supports the development of fully 3-dimensional approaches to unraveling deformation from successive airborne LiDAR scans of a fault zone. The focus of the project is the before and after airborne lidar scans of the April 4, 2010 El Mayor-Cucapah (EMC) earthquake rupture in northern Baja California, Mexco. The project objectives address three challenges in working with this data set: (1) reprocessing of the pre-earthquake data to reduce scanning artifacts and improve accuracy; (2) development of methods for rigorous, high-resolution displacement measures from point-cloud data of vastly different resolutions (9 to 18 pts/m2 post-earthquake compared with 0.013 pts/m2 pre-earthquake); (3) preliminary 3-D mechanical modeling of fault-zone deformation from this event. Meeting these challenges will advances knowledge of fault-zone deformation gained from this earthquake, as well as advance techniques for analysis of the next earthquake captured by differential LiDAR -- quite possibly along one of the numerous active faults imaged as part of the Earthscope facility.Coseismic surface rupture is an important, accessible record of earthquake slip, and the primary record of prehistoric seismicity. Near-field deformation measurements from differential LiDAR can transform our understanding of how coseismic surface ruptures are produced and distributed within fault zones. New knowledge to be gained includes understanding the mechanical coupling of fault slip to near-field distributed deformation, quantifying distributed components of fault slip otherwise difficult to measure, and predicting the style, extent, and magnitude of high strains around fault zones that could damage buildings and critical infrastructure. The techniques developed for this project will also prove valuable for other applications, such as in geomorphology, civil engineering, and robotics. This research brings together the expertise from five U.S.-based research groups that are leaders in the study of differential airborne LiDAR: UC Davis, Arizona State, UC San Diego, University of Houston, and Caltech / USGS. This project also broadens international collaborations formed following the EMC earthquake by involving researchers and students from CICESE, Baja California, in the development and deployment of new differential LiDAR algorithms and the open-source LiDAR-visualization software.