Anisotropic S-Wave Tomography at the Eastern North American Margin: Constraints on Mantle Structure and Dynamics
Session: Amphibious Seismic Studies of Plate Boundary Structure and Processes [Poster]
Type: Poster
Date: 4/20/2021
Presentation Time: 04:15 PM Pacific
Description:
The eastern North American passive margin (ENAM) is the ultimate result of the rifting of North America from Africa and Europe during the breakup of Pangea. As part of the ENAM Community Seismic Experiment designed to target this GeoPRISMS focus site, a 2014-2015 deployment of ocean-bottom seismometers (OBS) off the coast of North Carolina extends broadband seismic coverage from the EarthScope Transportable Array across the ocean-continent transition of the rifted passive margin. Shear wave splitting results in the area, which indicate seismic anisotropy and –by proxy– mantle dynamics, show several unexplained patterns. For instance, neither margin-parallel offshore fast azimuths nor null splitting on the continental coast obviously accord with margin-perpendicular continental extension or the current motion of the North American plate. Shear wave splitting, however, offers no depth constraint on anisotropy, and mantle structures have not been imaged in detail below the ocean-continent transition using the ENAM-CSE OBSs.
Using teleseismic travel times and shear wave splitting delay times measured at OBS, Transportable Array, and regional network stations, we conduct joint isotropic/anisotropic S- and S(K)KS-wave velocity tomography. Our velocity model, which accounts for the trade-off between azimuthal anisotropy and velocity, shows several anomalies which may be associated with edge-driven convection, delamination, or the edge of the subducted Farallon slab. We find multiple layers of anisotropy which suggest depth varying mantle flow. The combined constraints on velocity and anisotropy provide new evidence for the structure and dynamics of the mantle across the ocean-continent transition of ENAM.
Presenting Author: Brennan R. Brunsvik
Student Presenter: Yes
Authors
Brennan Brunsvik Presenting Author Corresponding Author brennanbrunsvik@ucsb.edu University of California, Santa Barbara |
Zachary Eilon eilon@ucsb.edu University of California, Santa Barbara |
Colton Lynner clynner@udel.edu University of Delaware |
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Anisotropic S-Wave Tomography at the Eastern North American Margin: Constraints on Mantle Structure and Dynamics
Category
Amphibious Seismic Studies of Plate Boundary Structure and Processes