Correlation Between Seismic Velocity and Anisotropy in the Western United States
Abstract
We compile a data set of new and previously published shear-wave splitting measurements in the western United States, for a total of 19,706 event-station pairs. Outside of cratonic regions, observations are generally consistent with an anisotropic layer at a depth of approximately 200 km with a laterally varying horizontal axis of symmetry, such as that produced by simple shear in the asthenosphere.
We find a remarkable degree of correspondence between the orientation of the symmetry axis and the seismic velocity structure of the upper mantle. Based on the assumption that anisotropy is due mostly to simple shear flow in the asthenosphere, we attempt to draw inferences about the physical characteristics associated with imaged seismic anomalies and density or strength variations controlling flow.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMDI21B0018N
- Keywords:
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- 3902 Creep and deformation;
- MINERAL PHYSICS;
- 7208 Mantle;
- SEISMOLOGY;
- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS