Collaborative Research: Constraints on Interseismic Deformation Offshore Oregon from Calibrated Continuous Pressure Records

合作研究：校准连续压力记录对俄勒冈州近海震间形变的约束

• 批准号: 1558477
• 负责人: William Wilcock
• 金额: $ 22.99万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-05-15 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558477&HistoricalAwards=false
• 关键词: Collaborative; Research; Constraints; Interseismic; Deformation

The Cascadia Subduction zone lies off the coast of the Pacific Northwest and is of both scientific and public interest because it is the site of catastrophic earthquakes similar to those that have occurred over the last decade in Japan, Chile, and Sumatra. On land, networks of instruments are available to measure the build-up of strain across the Cascadia subduction zone fault. Similar observations are required offshore to understand the dynamics of the subduction zone better, and to place stronger constraints on the earthquakes and tsunamis the fault produces every few hundred years. This project uses calibrated seafloor pressure sensors to make accurate measurements of the elevation of the seafloor at six sites off the coast of central Oregon. The project will initiate a decadal study that will measure changes in seafloor elevation that result from the build-up, and potentially the release, of strain across the subduction zone fault. The study will constrain the width of the locked portion of the fault that will break in the next large subduction zone earthquake. The project will involve two graduate students, and include at least four undergraduates on each research expedition.High-quality offshore vertical geodetic measurements will be used to provide a baseline suitable for resolving secular strain caused by locking across the Cascadia subduction zone, and for detecting slow slip events. Several previous studies have shown that seafloor pressure measurements can detect slow-slip events, but the drift of seafloor pressure sensors has limited their application to measuring secular strain. The University of Washington (UW) and Scripps Institution of Oceanography (SIO) have collaborated to build and successfully test a campaign version of the SIO seafloor calibrated pressure recorder, the Absolute Seafloor Calibrated Pressure Recorder (ASCPR). This instrument measures absolute pressures to an accuracy equivalent to ~1 cm of water depth. Repeat measurements with the ASCPR on stable seafloor benchmarks equipped with a continuously recording bottom pressure gauge will be used to remove the drift from pressure time series and enable measurements of secular strain. The UW and SIO have deployed a trench-perpendicular profile of 6 benchmarks and bottom pressure recorders off central Oregon. This project supports repeat campaign-style absolute pressure measurements over two years on each benchmark to fully characterize the repeatability of ASCPR measurements and initiate a decadal study required to measure secular strain. By utilizing stable, undisturbed benchmarks to make accurate absolute pressure measurements, this effort could transform our capabilities for making long-term geodetic observations offshore. Complementary geodetic and physical oceanographic modeling studies are being used to further understand the expected geodetic signals and develop improved methods to separate geodetic and oceanographic components of pressure.

卡斯卡迪亚俯冲带位于太平洋西北海岸附近，具有科学和公共利益，因为它是类似于过去十年在日本、智利和苏门答腊岛发生的灾难性地震的地点。在陆地上，仪器网络可用于测量卡斯卡迪亚俯冲带断层上应变的积累。为了更好地了解俯冲带的动态，并对断层每隔几百年产生的地震和海啸施加更强的限制，需要在近海进行类似的观测。 该项目使用经过校准的海底压力传感器来精确测量俄勒冈州中部海岸附近六个地点的海底高度。 该项目将启动一项十年研究，测量由于俯冲带断层应变的积累和潜在释放而导致的海底海拔变化。 这项研究将限制在下一次俯冲带大地震中断裂的断层锁定部分的宽度。该项目将涉及两名研究生，每次研究探险至少包括四名本科生。高质量的海上垂直大地测量将用于提供适合解决卡斯卡迪亚俯冲带锁定引起的长期应变的基线，并用于检测慢滑事件。先前的几项研究表明，海底压力测量可以检测慢滑移事件，但海底压力传感器的漂移限制了它们在测量长期应变方面的应用。华盛顿大学 (UW) 和斯克里普斯海洋学研究所 (SIO) 合作构建并成功测试了 SIO 海底校准压力记录仪的活动版本，即绝对海底校准压力记录仪 (ASCPR)。 该仪器测量绝对压力的精度相当于约 1 厘米水深。 在配有连续记录底部压力计的稳定海底基准上使用 ASCPR 进行重复测量，将用于消除压力时间序列中的漂移并实现长期应变的测量。 UW 和 SIO 在俄勒冈州中部附近部署了 6 个基准线和底部压力记录仪的垂直于海沟的剖面。该项目支持在两年内对每个基准重复进行运动式绝对压力测量，以充分表征 ASCPR 测量的可重复性，并启动测量长期应变所需的十年研究。通过利用稳定、不受干扰的基准进行准确的绝对压力测量，这项工作可以改变我们在海上进行长期大地测量观测的能力。互补的大地测量和物理海洋学建模研究正在用于进一步了解预期的大地测量信号，并开发改进的方法来分离压力的大地测量和海洋学分量。