Airborne Laser Swath Mapping of the Southern San Andreas Fault

该项目使用机载激光条带测绘（ALSM）技术（也称为LIDAR）对圣安德烈亚斯断层（SAF）和加州南部的其他选定断层段进行极高分辨率地形测量。在这次调查中获得的航空摄影将覆盖在地形数据集上，以产生断层近场地球表面的高度详细的表征。 其目的是在下一次大地震（即“大地震”）发生之前对断层系统进行详细成像，以便在此事件发生时能够以前所未有的精度绘制近场位移和变形场。断层系统的事后调查将确定滑动和后滑的不均匀性，因此有助于解决震源物理学中几个长期存在的争论。它也将有可能表征近场变形与沿走向过渡从连续蠕动到完全锁定部分的SAF。该项目广泛利用了新的国家机载激光测绘中心设施以及联合国航空和宇宙航行委员会公司。设施（借用全球定位系统（GPS）接收器，以支持飞机定位）。NCALM设施将使用佛罗里达大学的飞机、激光雷达和数码相机获取调查数据。飞机将在低空（~600米）运行，以确保出色的水平分辨率和垂直精度。它将沿着大致以断层为中心的平行轨道沿着飞行，以获得重叠的条带：这种地面覆盖的冗余将能够进行系统的质量控制，并提供一种避免陡峭地形中阴影问题的方法。该飞机将使用惯性制导和GPS组合进行定位。飞机的动态GPS定位将利用沿飞行路径每30公里沿着建立的众多GPS基站。ALSM数据首先将由NCALM使用其标准数据处理技术进行分析。点云（X、Y、Z和强度）观测结果将提供给俄勒冈州立大学，后者将与地面实况数据进行比较，以提供外部验证。一旦验证的原始数据和最初的“裸地球”数字高程模型（DEM）将被释放到一般的科学界通过NCALM数据档案在加州大学伯克利分校。这可能需要大约6个月的时间。这些数据将在俄勒冈州立大学以更悠闲的速度重新分析，看看是否可以做出更多的改进。OSU团队成员还负责将ALSM调查期间获得的数字照片叠加到初步和最终DEM上。一旦注册过程完成，合并后的产品将与广泛的现有影像和地形数据集绑定，包括：1）通过美国航天局-美国地质调查局的合作努力获得的ASTER、MODIS和Landsat高光谱图像数据，2）美国航天局和喷气推进实验室提供的SRTM地形数据，3）美国地质调查局从国家高程数据集提供的地形数据，3）2002年底由EarthData International使用GeoSAR获得的NOAA海岸服务中心地形数据，4）航空照片，例如，为美国地质调查局飞行的低太阳角、高分辨率布景以及摄影测量公司飞行的库存照片，5）美国地质调查局绘制的显示断层带地貌和偏移的详细地图（例如，Brown，1970; Clark，1984; Wallace，1990）。

Airborne Laser Swath Mapping of the Southern San Andreas Fault This project is using Airborne Laser Swath Mapping (ALSM) technology, also known as LIDAR, to perform a very high resolution topographic survey of the San Andreas fault (SAF) and other selected fault segments in southern California. Aerial photography obtained during this survey will be draped over the topographic dataset to produce a highly detailed characterization of the earth's surface in the near field of the fault. The intent is to image the fault system in great detail prior to the next great earthquake, i.e. the 'Big One', so that when this event occurs it will be possible to map the near-field displacement and deformation field with unprecedented accuracy. Post-event resurveys of the fault system will determine slip and afterslip heterogeneity, and so help resolve several long-standing debates in earthquake source physics. It will also be possible to characterize near-field deformation associated with the along-strike transition from continuously-creeping to fully-locked sections of the SAF. The project makes extensive use of the new National Center for Airborne Laser Swath Mapping (NCALM) facility, as well as the UNAVCO Inc. facility (to borrow Global Positioning System (GPS) receivers to support aircraft positioning). The NCALM facility will acquire the survey data using the University of Florida's aircraft, LIDAR and digital camera. The aircraft will operate at low altitude (~600 m) to ensure excellent horizontal resolution and vertical accuracy. It will fly along sets of parallel tracks, roughly centered on the fault, so as to obtain sets of overlapping swaths: this redundancy in ground coverage will enable systematic quality control, and provide a means to avoid shadowing problems in steep terrain. The aircraft will be positioned using a combination of inertial guidance and GPS. Kinematic GPS positioning of the aircraft will make use of numerous GPS base stations established every 30 km along the flight path. The ALSM data will at first be analyzed by NCALM using their standard data processing techniques. The point cloud (X,Y, Z and intensity) observations will be provided to OSU, who will then compare them with ground truth data so as to provide external validation. Once validated the raw data and the initial 'bare earth' digital elevation model (DEM) will be released to the general scientific community via the NCALM data archive in UC Berkeley. Probably, this will take about 6 months. The data will be reanalyzed at a more leisurely pace at OSU to see if additional improvements can be made. The OSU team members are also be responsible for draping the digital photography obtained during the ALSM survey onto the preliminary and final DEMs. Once this registration process is complete, the combined product will be tied to a wide range of existing imagery and topographic datasets, including: 1) ASTER, MODIS and Landsat hyperspectral imagery data available through NASA-USGS cooperative efforts, 2) SRTM topographic data from NASA and JPL, 3) USGS topographic data from the National Elevation Dataset, 3) NOAA Coastal Services Center topographic data acquired in late 2002 by EarthData International using GeoSAR, 4) air photos, e.g., low sun-angle, high resolution sets that were flown for the USGS as well as stock photography flown by photogrammetry companies, 5) detailed maps by USGS showing fault zone geomorphology and offsets (e.g., Brown, 1970; Clark, 1984; Wallace, 1990).