Collaborative Research:  Assessing the State of Locking on the Frontal Thrust of the Cascadia Subduction Zone With Seafloor Geodesy

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项目编号	1657961
	Collaborative Research: Assessing the State of Locking on the Frontal Thrust of the Cascadia Subduction Zone With Seafloor Geodesy
	C. David Chadwell
主持机构	University of California-San Diego Scripps Inst of Oceanography
项目开始年	2017
	2017-09-01
项目结束日期	2020-08-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	420636(USD)
国家	美国
语种	英语
英文摘要	The Cascadia Subduction Zone lies along the coast of Northern California, Oregon and Washington and is a significant geohazard that can generate great earthquakes and tsunamis. The Cascadia subduction zone is formed by the oceanic Juan de Fuca tectonic plate moving downward and beneath the overriding continental North American tectonic plate. The interface surface along which the two plates interact or rub is called the megathrust fault. As the Juan de Fuca plate moves downward, friction on the megathrust bends and contracts the overriding North American plate. The rate of buildup of strain is at the level of a centimeter or so per year, but eventually this stored energy is released causing a large earthquake and tsunami. The last great event occurred in 1700 and was powerful enough that the tsunami waves were recorded in Japan. Since that time the US Coast has become heavily populated posing a large hazard to society. Land-based GPS measurements can measure the slow accumulation of strain buildup, but the coastal sites are too far from the submerged shelf of the North American plate to provide reliable estimates far offshore. It is this offshore region where the tsunami generation may be greatest. This project uses GPS measured at the sea surface on a small robotic platform, combined with acoustic ranging from the platform to sensors on the seafloor. This technique is called GPS-Acoustic and can measure the centimeter-level motion of the seafloor. The project goal is to better document how much the seafloor is displacing and aid assessment of the potential size of the future tsunamis. This project will look for locking along the outer toe of the deformation front on the Cascadia Subduction Zone. Two new seafloor GPS-Acoustic sites at 43.0N and 45.3N will be added to the array of two recently established sites at 44.4N and 46.7N, and will allow for a determination of their motion relative to the North American plate. All of these sites are located several km inboard of the trench, and their motions will constrain the kinematics of the shallowest section of the frontal thrust. The project will use new lower cost methods that include GPS-Acoustic data that are collected from a Wave Glider rather than from an expensive ship. Permanent seafloor benchmarks will also be installed to extend the position time series indefinitely, and utilize commercial transponders that are reusable. Specifically, the re-purposing of seafloor transponders will be demonstrated by recovering and re-deploying an existing set of transponders. At the end of the three-year project, the six transponders at the two new sites will be recovered for reuse in future proposed projects of community interest. The benchmarks at these two new sites remain and can be re-occupied in the future (years to decades) to update the measurement time series. To interpret the motions inferred from the GPS-A observations, these offshore data will be integrated with existing onshore GPS and leveling observations, which will allow for a range of locking models to be explored. The project will also compare the four along-strike observations to each other, and correlate with along-strike variations in geologic and structural patterns.
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文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/71888
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	C. David Chadwell.Collaborative Research: Assessing the State of Locking on the Frontal Thrust of the Cascadia Subduction Zone With Seafloor Geodesy.2017.