Identifying Moho depths and velocity anomalies in the uppermost mantle of the Mississippi Embayment from Pn tomography and anisotropy studies
Abstract
Lateral depth variations of the Mohorovicic discontinuity, Pn velocities, and anisotropy features at uppermost mantle depths below the central U.S. are determined using Pn tomography. Excellent raypath coverage throughout the northern Mississippi Embayment (ME) is obtained using the NELE (Northern Embayment Lithosphere Experiment) and US TA (Transportable Array) datasets. High Pn velocities are present below the northern portion of the Reelfoot Rift and the New Madrid seismic zone. Prominent regions of low velocity are present to the east and north of the ME, in agreement with recent teleseismic tomography studies indicating the presence of low P- and S-wave velocities in the uppermost mantle. A prominent region of low velocity coincides with the southwestern portion of the Illinois Basin. Higher velocities are located west of the Illinois Basin and west of the Ozark Plateau. Crustal thicknesses obtained from the Pn station delays indicate thinner crust in the southern Coastal Plain and ME and thicker crust north of the ME. Strong Pn anisotropy and rotation of the fast directions are associated with the northern ME. Fast directions differ from present absolute plate motion directions and from fast directions determined from SKS splitting, suggesting the presence of multiple anisotropic layers. Parameter errors estimated using the bootstrap method are all less than 0.1 km/s for velocity and magnitude of the anisotropy.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.T23E0655B
- Keywords:
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- 8109 Continental tectonics: extensional;
- TECTONOPHYSICS;
- 8158 Plate motions: present and recent;
- TECTONOPHYSICS;
- 8159 Rheology: crust and lithosphere;
- TECTONOPHYSICS;
- 8170 Subduction zone processes;
- TECTONOPHYSICS