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TitleCrustal structure offshore Vancouver Island from bayesian receiver function inversion of NEPTUNE seismic data
AuthorBrillon, C D; Cassidy, J F; Dosso, S E; Willcock, W; Hooft, E; Toomey, D; McGill, P
SourceCanadian Geophysical Union Annual Meeting, abstracts volume; 2011 p. 14-15
Alt SeriesEarth Sciences Sector, Contribution Series 20110118
MeetingCanadian Geophysical Union joint CSAFM Annual Meeting; Banff; CA; May 15-18, 2011
Mediaon-line; digital
File formatpdf
ProvinceWestern offshore region
Subjectsgeophysics; seismic interpretations; seismic risk; seismology; seismic surveys; seismicity; earthquake risk; Juan de Fuca Plate
ProgramTargeted Hazard Assessments in Western Canada, Public Safety Geoscience
AbstractThis paper inverts receiver functions based on passive seismic data recorded by NEPTUNE (North-east Pacific Time-series Undersea Networked Experiments) to obtain a crustal model of the Juan de Fuca plate. In previous receiver function studies in northern Cascadia, knowledge of offshore structure was limited due to an absence of seismic monitoring in oceanic areas. The introduction of NEPTUNE, a cabled real-time seabed observatory offshore Vancouver Island, British Columbia, has expanded the research possibilities of many disciplines including receiver function analysis. Data from three permanent NEPTUNE broadband seismographs, as well as two previously deployed KECK autonomous broadband ocean bottom seismometers are used here to determine the Moho depth, and therefore the crustal thickness of the Juan de Fuca plate. This work will ultimately lead to the first structural model of the Juan de Fuca Plate from the spreading ridge to the subduction deformation front.
We utilize three-component, broadband recordings of large (M6+), distant (30°-100°) earthquakes to compute receiver functions. These are characterized by locally generated P-to-S wave converted phases (Ps) and provide information on the shear wave velocity (vs) structure directly beneath the recording sites.
Bayesian inversion is applied to NEPTUNE teleseismic data to provide marginal probability profiles of shear wave velocity, including the most probable model of the oceanic crust. Using a preliminary dataset of teleseismic events, results show that on the axial segment of the Juan de Fuca ridge and abyssal plain (mid-plate), sediments are thin (<500 m) and underlain by 5-7 km of flat crust, while towards the east, sediments thicken and structure becomes more complex as the Juan de Fuca plate begins to subduct beneath the North American plate.