Seismic crustal structure beneath the BC convergent margin

俯冲的大洋板块和上覆的大陆板块之间的界面目前处于锁定状态，正在积累能量，这些能量将在未来类似1700年9级地震的大地震中释放出来。然而，我们不知道地震是否会使海底破裂，并促成海啸的产生。目前，甚至连温哥华岛外海域是否发生过小规模地震这样的基本信息都缺乏。这些信息对于向公众通报地震、海啸和海底滑坡危害提供科学依据至关重要，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厅(JAMSTEC)的地震学家合作，部署了33台海底地震仪(OBS)，为期3个月。此外，来自伍兹霍尔海洋研究所的10个宽带OBS(目前部署为期1年)加上2个近乎实时的海王星-加拿大宽带仪器构成了我们电网的一部分。该项目的第二阶段计划在2012年进行，将在更有针对性的研究中部署约35个日本OBSS。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。宽带仪器还将允许我们记录“极低频率地震”，这是一种通常与低幅度地震有关的慢滑事件。 陡坡上的水下滑坡可能与天然气水合物的存在有关，天然气水合物是海底以下约250米处上部的“冻结”甲烷。另一个因素可能是大约15,000年前最后一次冰川盛期之后发生的快速沉积。然而，滑坡的实际触发因素可能是当地的地震。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限制因素，来检查给定地震震动程度下陡峭山脊的稳定性。地震也可能是海底甲烷喷口流体流量增加的触发因素，因此我正在使用声学技术实时监测气泡流，仪器连接到海王星光纤电缆。

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.