Seismic crustal structure beneath the BC convergent margin

BC汇聚边缘下方的地震地壳结构

• 批准号: 156159-2011
• 负责人: Spence, George
• 金额: $ 2.4万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=569503
• 关键词: Seismic; crustal; structure; beneath; BC

The interface between the underthrust oceanic plate and over-riding continental plate is currently locked and accumulating energy which will be released in a future great earthquake similar to the magnitude 9 event in 1700. However, we do not know whether the earthquake will rupture the seafloor and contribute to tsunami generation. At present, there is a lack of information as basic as whether there are even any small earthquakes in the region offshore Vancouver Island. Such information is critical to provide the scientific basis for informing the public of earthquake, tsunami and seafloor-landslide hazards, and may help prevent the potential loss of life. In collaboration with researchers at the Geological Survey of Canada and seismologists at the Japan Agency for Marine-Earth Science & Technology (JAMSTEC), I deployed 33 ocean bottom seismometers (OBSs) from JAMSTEC for a 3-month period in summer 2010. As well, 10 broadband OBSs from Woods Hole Oceanographic Institution (currently deployed for 1-year period) plus 2 near-real-time NEPTUNE-Canada broadband instruments form part of our grid. Phase 2 of the project is planned in 2012, with ~35 Japanese OBSs to be deployed in a more focused study. We anticipate that these deployments will allow us to detect earthquakes at an unprecedented sensitivity. The broadband instruments will also allow us to record "Very Low Frequency Earthquakes", slow-slip events often associated with low-amplitude seismic tremor. Underwater landslides on steep slopes may be linked to the presence of gas hydrate, "frozen" methane in the upper ~250 m below the seafloor. Another factor may be rapid sedimentation that occurred after the last glacial maximum ~15,000 years ago. However, the actual trigger for the slide may be a local earthquake. My study will examine the stability of steep ridges for a given degree of earthquake shaking, by incorporating constraints such as the thickness of gas hydrate and the nature of the shallow sediments. Earthquakes may also act as triggers for increased fluid flow at seafloor methane vents, and so I am using acoustic techniques to monitor bubble streams in real-time, with an instrument connected to the NEPTUNE fibre-optic cable.

俯冲的海洋板块和上覆的大陆板块之间的界面目前被锁定并积累能量，这些能量将在未来类似于1700年9级地震的大地震中释放。然而，我们不知道地震是否会使海底破裂并导致海啸的产生。目前，在温哥华岛近海地区是否有任何小地震这样的基本信息还缺乏。这些信息对于向公众提供地震、海啸和海底滑坡危险的科学依据至关重要，并可能有助于防止潜在的生命损失。2010年夏天，我与加拿大地质调查局的研究人员和日本海洋地球科学技术机构（JAMSTEC）的地震学家合作，部署了33台JAMSTEC海底地震仪（OBS），为期3个月。此外，伍兹霍尔海洋研究所的10个宽带海洋观测系统（目前部署了1年）加上2个近实时海王星-加拿大宽带仪器构成了我们网格的一部分。该项目的第二阶段计划于2012年进行，将在一项重点更突出的研究中部署约35个日本OBS。我们预计，这些部署将使我们能够以前所未有的灵敏度探测地震。宽带仪器还将使我们能够记录“甚低频地震”，即通常与低振幅地震震颤相关的慢滑动事件。 陡坡上的水下滑坡可能与海底以下约250米处的天然气水合物（“冻结”甲烷）的存在有关。另一个因素可能是15，000年前末次盛冰期后发生的快速沉积。然而，滑坡的实际触发因素可能是当地地震。我的研究将通过考虑天然气水合物的厚度和浅层沉积物的性质等约束条件，来研究陡峭山脊在给定地震震动程度下的稳定性。地震也可能是海底甲烷喷口流体流动增加的触发器，因此我正在使用声学技术来实时监测气泡流，并将仪器连接到海王星光纤电缆。