The impact of crustal structures on multiple frequency and waveform tomography of Antarctica

We present two preliminary tomography models of Antarctica using seismic data recorded globally since 1994. Through combined efforts, several seismic broadband arrays have been deployed in Antarctica in previous decades, enabling the generation of two types of tomography models in this study: a multiple-frequency body-wave tomography and a waveform tomography model. Altogether, more than 2000 global events are collected resolving this region in great detail.

Crustal correction is crucial in seismic tomography, as it can cause the crustal smearing or leakage of shallow heterogeneities into the deep mantle. In global multiple-frequency tomography, synthetic seismograms are calculated on a spherically symmetric earth model (e.g. PREM, IASP91) in which effects of the crust, ellipticity, and topography are neglected. At a later stage, corrections are applied to the measured traveltimes to account for the known deviations from spherically symmetric earth models.

In waveform tomography, the crust has a significant impact on the Rayleigh and Love wave speeds. We invert for the crustal structure and explicitly account for its highly non-linear effects on seismic waveforms. Here, we implement a flexible workflow where different 3D reference crustal models can be plugged in. We test this using the CRUST2.0 and CRUST1.0 models.

In this study, we quantify the effects of these crustal models on two types of inversion techniques with a focus on the mantle structure beneath Antarctica. We compare the mantle structures beneath Antarctica imaged by a multiple-frequency body-wave tomography technique (e.g., Hosseini et al, 2019) and a waveform tomography method (Lebedev et al. 2005; Lebedev and van der Hilst 2008) using CRUST1.0 and CRUST2.0.

References:
K. Hosseini, K. Sigloch, M. Tsekhmistrenko, A. Zaheri, T. Nissen-Meyer, H. Igel, Global mantle structure from multifrequency tomography using P, PPand P-diffracted waves, Geophysical Journal International, Volume 220, Issue 1, January 2020, Pages 96–141, https://doi.org/10.1093/gji/ggz394

S. Lebedev, R. D. Van Der Hilst, Global upper-mantle tomography with the automated multimode inversion of surface and S-wave forms. Geophysical Journal International, Volume 173, Issue 2, May 2008, Pages 505–518, https://doi.org/10.1111/j.1365-246X.2008.03721.x

A. J. Schaeffer, S. Lebedev, Global shear speed structure of the upper mantle and transition zone, Geophysical Journal International, Volume 194, Issue 1, 1 July 2013, Pages 417–449, https://doi.org/10.1093/gji/ggt095