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: 1558468
• 负责人: Mark Zumberge
• 金额: $ 36.09万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 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 2018-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558468&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部海岸外，具有科学和公共利益，因为它是灾难性地震的发生地，类似于过去十年在日本、智利和苏门答腊岛发生的地震。在陆地上，可以使用仪器网络来测量卡斯卡迪亚俯冲带断层上的应变积累。为了更好地了解俯冲带的动力学，并对断层每几百年产生一次的地震和海啸施加更强的约束，需要在近海进行类似的观测。该项目使用校准的海底压力传感器对俄勒冈州中部海岸外六个地点的海底高度进行准确测量。该项目将启动一项十年研究，以测量海底高度的变化，这些变化是由于俯冲带断层上应变的积累和潜在的释放造成的。这项研究将限制断层锁定部分的宽度，该部分将在下一次大俯冲带地震中破裂。该项目将涉及两名研究生，每一次研究探险至少包括四名本科生。将使用高质量的近海垂直大地测量来提供适合于解决卡斯卡迪亚俯冲带锁定造成的长期应变的基线，并用于探测慢滑事件。先前的几项研究表明，海底压力测量可以检测到慢滑事件，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)和斯克里普斯海洋研究所(SIO)合作建造并成功测试了SIO海底校准压力记录仪的运动版，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厘米的水深。将使用ASCPR对配备了连续记录海底压力计的稳定海底基准进行重复测量，以消除压力时间序列中的漂移，并能够测量长期应变。UW和SIO在俄勒冈州中部附近部署了6个基准和底部压力记录器的垂直沟槽剖面。该项目支持在两年内对每个基准进行重复运动式绝对压力测量，以充分表征ASCPR测量的重复性，并启动测量长期应变所需的十年研究。通过利用稳定的、不受干扰的基准来进行准确的绝对压力测量，这一努力可能会改变我们进行海上长期大地测量观测的能力。正在利用互补的大地测量和物理海洋模拟研究，以进一步了解预期的大地测量信号，并改进分离压力的大地测量分量和海洋分量的方法。