Radial Anisotropy of Antarctica From Surface Wave Ambient Noise Tomography

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

Antarctica is the most southern continent on Earth, where permanent ice covers more than 95% of the surface. The harsh climate and remoteness hinder data collection and require that we obtain optimal results from sparse seismic networks. Whereas most seismic studies invert only Rayleigh wave data, Love wave phase and group velocities provide better resolution of shallow crustal structure as well as allow for evaluation of radial anisotropy. In this study, we derive crustal and uppermost mantle shear wave velocity model for the West Antarctica and part of East Antarctica using both interstation Love and Rayleigh wave Greens functions estimated from cross-correlation of ambient noise records. We use all available broadband data collected in Antarctica over the past 18 years, including that from recent temporary arrays such as TAMSEIS, AGAP, TAMNNET, RIS and POLENET/ANET. We use a time-frequency phase-weighted stacking method, that expands the reliable period range of Love wave group and phase velocity measurements from 6 – 30 s to 6 – 40 s and, compared with linear stacking, permits many more station pairs to be analyzed. Group and phase velocity maps of both Rayleigh and Love waves are obtained and are then inverted for a shear wave velocity structure using a Monte Carlo inversion method. Most of the major features of the V_SH structure are consistent with the V_SV structure derived by Heeszel et al.(2016) and Shen et al.(2018) that inverted Rayleigh waves alone inversion.Major geological features in Antarctica,such as the thick sediments in the Ross Embayment and the crustal root beneath the Gamburtsev Subglacial Mountains are evident in the V_SH structure.However, some shallow structural details are visible in the V_SH structure that were not seen in V_SV structure,such as the Polar Subglacial Basin and the Byrd Subglacial Basin.Joint inversion of Love and Rayleigh wave data allows us to determine the radial anisotropic structure of the crust and uppermost mantle,and the uppermost mantle of West Antarctica shows strong positive (V_SH > V_SV) radial anisotropy.

Presenting Author: Zhengyang Zhou

Authors