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

卡斯卡迪亚俯冲带位于太平洋西北海岸外，是科学界和公众都感兴趣的地方，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，仪器网络可用于测量横跨卡斯卡迪亚俯冲带断层的应变积累。为了更好地了解俯冲带的动态，并对断层每几百年产生的地震和海啸进行更严格的限制，需要在近海进行类似的观察。该项目使用经过校准的海底压力传感器，对俄勒冈州中部海岸外的六个地点的海底高度进行精确测量。该项目将启动一项为期十年的研究，测量海底高度的变化，这些变化是由俯冲带断层的应变积累和潜在的释放造成的。这项研究将限制在下一次大的俯冲带地震中断裂的断层锁定部分的宽度。该项目将包括两名研究生，以及至少四名本科生参加每次研究考察。高质量的海上垂直大地测量数据将用于提供一个基线，适用于解决由Cascadia俯冲带锁定引起的长期应变，并用于检测慢滑事件。先前的一些研究表明，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）和斯克里普斯海洋学研究所（SIO）合作建立并成功测试了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）。这个仪器测量绝对压力的精度相当于~1厘米的水深。使用ASCPR在稳定的海底基准上重复测量，并配备连续记录的底部压力表，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在俄勒冈州中部部署了6个基准和底部压力记录仪的海沟垂直剖面。该项目支持在每个基准上进行为期两年的重复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。通过使用稳定、不受干扰的基准来进行精确的绝对压力测量，这项工作可以改变我们在海上进行长期大地测量的能力。正在利用互补的大地测量和物理海洋学模拟研究来进一步了解预期的大地测量信号，并发展分离压力的大地测量和海洋分量的改进方法。

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.