SKS SPLITTING: Using Seismic Waves to Understand Mantle Structure

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Presentation transcript:

SKS SPLITTING: Using Seismic Waves to Understand Mantle Structure Tiegan Hobbs – 260309530 Geodynamics and Geomagnetism October 5th, 2011

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

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

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

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

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.

RESULTS