Collaborative Research: Seismic Imaging of Aseismic Transients

合作研究：地震瞬变的地震成像

• 批准号: 0409024
• 负责人: Fenglin Niu
• 金额: --
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-15 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409024&HistoricalAwards=false
• 关键词: Collaborative; Research; Seismic; Imaging; Aseismic

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).

南圣安德烈亚斯断层机载激光测绘带测绘 该项目使用机载激光测绘带测绘 (ALSM) 技术（也称为 LIDAR）对圣安德烈亚斯断层 (SAF) 和南加州其他选定的断层段进行超高分辨率地形测量。此次勘测期间获得的航空摄影将覆盖在地形数据集上，以生成断层近场地球表面的高度详细特征。 目的是在下一次大地震（即“大地震”）之前对断层系统进行详细成像，以便在该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图。断层系统的事后重新调查将确定滑动和后滑动的非均质性，从而有助于解决震源物理学中几个长期存在的争论。还可以表征与 SAF 从连续蠕动部分到完全锁定部分的沿走向过渡相关的近场变形。该项目广泛利用了新的国家机载激光测绘中心 (NCALM) 设施以及 UNAVCO Inc. 设施（借用全球定位系统 (GPS) 接收器来支持飞机定位）。 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。该飞机将在低空（~600 m）运行，以确保出色的水平分辨率和垂直精度。它将沿多组平行轨道飞行，大致以断层为中心，以获得多组重叠的条带：地面覆盖的这种冗余将实现系统的质量控制，并提供一种避免陡峭地形中阴影问题的方法。飞机将结合惯性制导和 GPS 进行定位。飞机的运动GPS定位将利用沿着飞行路径每30公里建立的众多GPS基站。 ALSM 数据首先由 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 OSU，OSU 然后将它们与地面真实数据进行比较，以提供外部验证。一旦验证了原始数据和初始“裸地”数字高程模型 (DEM)，将通过加州大学伯克利分校的 NCALM 数据档案向广大科学界发布。大概，这需要大约 6 个月的时间。俄勒冈州立大学将以更悠闲的速度重新分析数据，看看是否可以做出额外的改进。 OSU 团队成员还负责将 ALSM 调查期间获得的数码照片覆盖到初步和最终的 DEM 上。注册过程完成后，组合产品将与各种现有图像和地形数据集绑定，包括：1) 通过 NASA-USGS 合作获得的 ASTER、MODIS 和 Landsat 高光谱图像数据，2) 来自 NASA 和 JPL 的 SRTM 地形数据，3) 来自国家高程数据集的 USGS 地形数据，3) NOAA 海岸服务中心于 2002 年末获取的地形数据 EarthData International 使用 GeoSAR 提供的数据；4) 航空照片，例如为 USGS 飞行的低太阳角、高分辨率照片以及摄影测量公司飞行的图库摄影；5) USGS 提供的显示断层带地貌和偏移的详细地图（例如，Brown，1970 年；Clark，1984 年；Wallace，1990 年）。