1. SKS SPLITTING: Using Seismic Waves to Understand Mantle Structure
Tiegan Hobbs –
Geodynamics and Geomagnetism
October 5th, 2011

2. BASIC IDEA
Measure anisotropy below seismic stations. Correlate it to deformation events, past and present. Infer structures from these deformations.

3. ANISOTROPY: “occurs when elastic waves vibrating or travelling in one direction travel faster than another” (Savage, 1999)
CAUSES:
Fabrics of otherwise isotropic material
Fluid-filled structures
Aligned anisotropic minerals
Notes from F.A. Darbyshire

4. Measure φ (direction) and δt (time delay)
After Savage et al. 1999

5. Olivine ‘A’ axes are usually aligned with extension or flow direction
Olivine ‘A’ axes are usually aligned with extension or flow direction. (Savage et al. 1999, p. 68, 79)
Sources of Deformation: (1) Fluid-filled Cracks (2) Lithospheric Deformation (3) Asthenospheric Flow

6. PROBLEMS: (1) Vertical Profile Transition Zone, D”, Lehmann Discontinuity (2) Back-Azimuthal Variation Lateral Variations, Dipping Layers, Multiple Layers? (3)Correlation to Surface & Tectonics Many possible orientations.

7. RESULTS