Upper mantle velocity structure of the Arabian Shield from body and surface wave

tomography

Andy Nyblade, Penn State University

Yongcheol Park, Korean Polar Research Inst.

Artie Rodgers, LLNL

Abdullah Al-Amri, King Saud University

Margins RCL workshop, April 30, 2009

• Limited station distribution in middle of the shield and large station spacing

• Limited resolution above 150 km depth and across middle of shield at all depths

• Favor single plume (Afar) or superplume model (African superplume)

Park et al. G-Cubed, 2007

• Limited station distribution in middle of the shield and large station spacing

• Limited resolution above 150 km depth and across middle of shield at all depths

• Favor single plume (Afar) or superplume model (African superplume)

Park et al. G-Cubed, 2007

Rayleigh wave tomographyPark et al. G-Cubed, 2008

1) Data: SANDSN; PASSCAL - S. Arabia, Ethiopia; GSN/FDSN

2) MFT (Dziewonski et al., 1969) used for interstation phasevelocities 3) Method of Lawrence et al., 2006 (modified from Menke & Levin, 2002) used to correct for wavefront distortion 4) 45 to 140 sec period

5) Method for inversion: LSQR (Paige and Saunders, 1982)

Inversion for structure

1) 1D models for each grid point using linearized iterative method of Julia et al (2003)

2) included group vel. 10-45 sec period from Pasyanos (2005)

3) Model parameterization: crust 4 or 5 layers (Crust 2.0), 10 km thick layers in mantle

4) Moho depth and Sn fixed to be consistent with previous results

5) Quasi-3D model obtained by combining 1D models (interpolating between them at 10 km depth intervals using min. curvature gridding algorithm)

Shield Platform

Shield Platform

Other relevant geophysical observations

1) Normal 410 and 660 km discontinuities (Kumar et al., 2002; Benoit et al., 2003)

2) Dynamic uplift (Daradich et al., 2003; Hansen et al., 2007)

3) Seismic anisotropy: N-S fabric (Hansen et al. 2007;Tkalcic et al., 2006)

4) Seismic models supportingAfrican superplume; lower-upper mantle connection(Benoit et al., 2006; Simmons etal., 2007; Ritsema et al., 1999)

Moho Depths

Crust 2.0 (Bassin et al., 2000)Al-Damegh et al., 2005; Kumar et

al., 2002; Mooney et al., 1985