EGU2020-12438
https://doi.org/10.5194/egusphere-egu2020-12438
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Northwest U.S. crustal seismic anisotropy suggests crustal flow driven by vertical loads in the underlying mantle

Eugene Humphreys1, Jorge Castellanos2, Robert Clayton2, Jonathan Perry-Houts1, YoungHee Kim3, Bart Niday1, and Christian Stanciu1
Eugene Humphreys et al.
  • 1Department of Earth Science, University of Oregon, Earth Science, Eugene, USA (genehumphreys@gmail.com)
  • 2Seismological Laboratory, Department of Earth and Planetary Sciences, Caltech, Pasadena, California 91125, USA
  • 3School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, Republic of Korea

Azimuthal anisotropy in the NW U.S. crust is derived using 3-17 s Rayleigh waves derived using ambient noise from about 300 broadband stations. Velocity is resolved between all station pairs in close proximity, and velocity as a function of azimuth is determined for each station. Azimuthal anisotropy orientations point strongly toward tomographically-imaged high-velocity structures in the underlying mantle, but show no relation to the underlying mantle anisotropy field. We suggest that the crustal anisotropy is decoupled from lateral tectonic forces and is created by upper mantle vertical loading, which in turn generates lateral pressure gradients that drive channelized flow in the ductile mid and lower crust. This idea is tested with geodynamic modeling. Using reasonable values for crustal viscosity and mantle buoyancy structure, we find that the local buoyancy sources within the upper mantle will drive the viscous crustal flow in a manner that reproduces well the imaged crustal anisotropy. We conclude that mantle vertical loading, acting independently from mantle flow, can actively control crustal deformation on a scale of several hundred kilometers.

How to cite: Humphreys, E., Castellanos, J., Clayton, R., Perry-Houts, J., Kim, Y., Niday, B., and Stanciu, C.: Northwest U.S. crustal seismic anisotropy suggests crustal flow driven by vertical loads in the underlying mantle, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12438, https://doi.org/10.5194/egusphere-egu2020-12438, 2020

This abstract will not be presented.

Displays

Display file