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.
