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Advancing the Resolution of Mid-Mantle Structures: Full-Waveform Box Tomography of the Yellowstone Mantle Plume

Description: 

The Yellowstone mantle plume is a narrow, low shear-velocity feature in the lower mantle, exhibiting a horizontal deflection at approximately 1000 km depth, similar to other plumes and subducted slabs, suggesting a rheological change at that level (Nelson and Grand, 2018). To improve resolution at mid-mantle depths, we utilize full waveforms of body and surface waves.

Employing 'box tomography', we integrate a global 3D solver, SPECFEM3D_globe (Tromp et al., 2008), for wavefield calculation outside the region of interest, and RegSEM (Cupillard et al., 2012) for internal computations using the Spectral Element Method (SEM). The background global 3D model, SEMUCB_WM1 (French and Romanowicz, 2014), which faintly resolves a low-velocity plume beneath Yellowstone extending to the core-mantle boundary (French and Romanowicz, 2015), is used for initial wavefield computations, which are recorded at the box boundaries. This includes body waveforms from distant quakes for mid- to lower-mantle structure illumination.

To conduct box tomography, we initially compute the required global wavefields in the reference 3D model down to a 20 s period and record these fields on the box boundaries. Inversion iterations within the box reduce the cutoff period from 40 s to 20 s, with depth range expansion. The crustal structure is constrained using surface wave dispersion data down to a 16 s period. Our results, derived from multiple inversion iterations using a Gauss-Newton optimization and a physics-based Hessian computed with normal mode perturbation theory (NACT, Li and Romanowicz, 1995), will be presented.

Session: Earth’s Structure from the Crust to the Core [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Utpal

Student Presenter: No

Invited Presentation: 

Authors