Structure of the Cascadia Margin Offshore Northern Oregon (44.5-46deg N) From Casie21-OBS Wide-Angle Seismic Profiles
Description:
The 2021 Cascadia Seismic Imaging Experiment ocean bottom seismometer deployment (CASIE21-OBS) is an NSF- and USGS-supported controlled-source marine seismic survey conducted offshore Cascadia in May-July 2021 (Carbotte et al., in review; Canales et al., 2023, doi:10.1785/0220230010). The main goal of CASIE21-OBS was to collect a modern, open-access wide-angle seismic reflection/refraction dataset that would enable scientists to develop P- and S-wave velocity models of the structure of the accretionary prism and down-going plate along most of the Cascadia margin between northern Vancouver Island and southern Oregon. In this presentation we report 2-D Vp models obtained from traveltime tomography of sedimentary (incoming and accreted), crustal and mantle arrivals recorded along three of the CASIE21-OBS profiles (PD10, PD12, and PD13). These profiles cross the Cascadia margin offshore northern Oregon between latitudes ~44.5°-46°N in a region that includes the offshore northern edge of the Franciscan terrane and variable offshore extension of the Siletz terrane —both of which are thought to play a role in the deformation characteristics of the accretionary prism and the geometry and deformation of the subducting Juan de Fuca plate (JdF)— as well as a transition from seaward to landward vergence near ~45°N. Profile to profile, our models document important along-strike variability in continental platform seismic velocities arising from the presence/absence of the accreted volcanic terranes. Profile PD13 in the seaward-vergent section of the margin shows more complex and heterogeneous seismic structure in both crustal and accreted sediments when compared to landward-vergent profiles PD10 and PD12. We tentatively attribute this difference to prevalence of fluid drainage fracture networks traversing the down-going JdF crust and slope sediments in seaward-vergent regions compared to stratigraphic-dominated fluid migration patterns in landward-vergent regions (e.g., Johnson et al., 2006, doi:10.2973/odp.proc.sr.204.125.2006).
Session: Seismology in the Oceans: Pacific Hemisphere and Beyond - I
Type: Oral
Date: 5/2/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Juan Pablo
Student Presenter: No
Invited Presentation:
Authors
Juan Pablo Canales Presenting Author Corresponding Author jpcanales@whoi.edu Woods Hole Oceanographic Institution |
Hanchao Jian hjian@whoi.edu Woods Hole Oceanographic Institution |
Michael Mann michael.mann@whoi.edu Brown University |
Nathan Miller ncmiller@usgs.gov U.S. Geological Survey |
Suzanne Carbotte carbotte@ldeo.columbia.edu Columbia University |
Shuoshuo Han han@ig.utexas.edu University of Texas at Austin |
Brian Boston boston@auburn.edu Auburn University |
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Structure of the Cascadia Margin Offshore Northern Oregon (44.5-46deg N) From Casie21-OBS Wide-Angle Seismic Profiles
Category
Seismology in the Oceans: Pacific Hemisphere and Beyond