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The origins of tectonic structures in East Antarctica, such as the Gamburtsev Subglacial Mountains (GSMs), the Wilkes Subglacial Basin (WSB), the Aurora Subglacial Basin (ASB), and the Transantarctic Mountains (TAMs), are not clearly understood. Previous investigations have proposed multiple origin models to explain the formation of these structures; however, existing tomographic images lack resolution and consistency given the sparse seismic coverage in East Antarctica. We use full-waveform ambient noise tomography to model the shear-wave velocity structure beneath East Antarctica to further investigate these features. We extract Rayleigh-wave Empirical Green’s Func-tions (EGFs) between periods of 15 and 340 secs from ambient seismic noise using a frequency time normalization technique. Synthetic waveforms are simulated through a 3-D heterogenous Earth model with a lateral grid spacing of 0.025º (~2.25 km) using a finite-difference wave propagation method. The synthetic seismograms are cross-correlated with the EGFs to measure the phase delays. The fi-nite-frequency sensitivity kernels are calculated using the scattering-integral approach and the shear-wave velocity model is computed by inverting the phase delays using a sparse damped least-square inversion method. Preliminary results show fast seismic velocities beneath the WSB, which may be associated with thick and stable lithosphere, and slow velocities beneath the ASB, possiblymore »
Upper mantle structure beneath Antarctica from full-waveform inversion constrained by long-period ambient seismic noiseLateral heterogeneity in the upper mantle beneath Antarctica has important implications to understanding the response of the Earth to changes in ice mass loss and estimates of geothermal heat flow. As seismic coverage and employed methodologies improve, lateral variations have been found in regions that were once assumed to be relatively uniform. Here we present the results from a full-wave inversion constrained by long-period (40-340 s) empirical Green’s functions (EGFs) extracted by using a frequency-time normalization approach and cross-correlating several decades worth of ambient seismic noise. Using the computational resources at the Alabama Supercomputing Authority, we simulate waveforms within a spherical, finite-difference grid. Phase delays are then measured by cross-correlating the EGFs and synthetic waveforms, sensitivity kernels are constructed using the scattering integral method, and the model is iteratively inverted to obtain a refined upper mantle structure. Preliminary results from our continental-scale model not only emphasize lateral variations in West Antarctica that have been observed in some previous models but also highlight distinct mantle anomalies beneath East Antarctica, many of which were previously unresolved. We will present our final model for the whole of Antarctica, illustrating how mantle heterogeneities are associated with different tectonic terranes, providing further constraints for heatmore »
Characterizing Crustal and Upper Mantle Structure in East Antarctica with Full-Waveform Ambient Noise TomographyThe thick ice coverage and harsh climatic conditions in East Antarctica hinder detailed investigations of tectonic features, leading to debates regarding the origin and evolution of the Gamburtsev Subglacial Mountains (GSM), the Wilkes Subglacial Basin (WSB), the Aurora Subglacial Basin (ASB), and the Transantarctic Mountains (TAMs). Present tomographic models lack resolution and consistency given the minimal seismic coverage in East Antarctica. To further such investigations, we are using full-waveform ambient noise tomography to model shear-wave velocities and to constrain the crustal and upper mantle structure beneath East Antarctica. This approach utilizes Empirical Green’s functions (EGFs), which provides information about the Earth structure between recording stations and is an alternative approach compared to many traditional tomographic models. EGFs from ambient seismic noise between periods of 15-340 secs are extracted using a frequency-time normalization approach, and synthetic waveforms are simulated through a three-dimensional heterogeneous Earth model using a finite-difference wave propagation method with a grid spacing of 0.025º (~ 2.25 km). Phase delays are computed by cross correlating EGFs and the synthetics, and sensitivity kernels are constructed using a scattering integral approach. Preliminary results show slow velocities beneath both the WSB and ASB, possibly reflecting old rift systems or other inherited tectonicmore »
Shear-wave Velocity Structure of the Crust and Upper Mantle beneath East Antarctica from Full-Waveform Ambient Noise TomographyThe origin and tectonic evolution of various features in East Antarctica, such as the Wilkes Subglacial Basin (WSB), Aurora Subglacial Basin (ASB), Transantarctic Mountains (TAMs), and Gamburtsev Subglacial Mountains (GSM), are unconstrained due to thick ice coverage and a lack of direct geologic samples. We are modeling the crustal and upper mantle structure beneath these areas using a full-waveform tomography method to further our understanding the tectonic evolution of the continent as well as the behavior of the overlying ice sheet. A frequency-time normalization approach is employed to extract empirical Green’s functions (EGFs) from ambient seismic noise, between periods of 15-340 seconds. EGF ray path coverage is dense throughout East Antarctica, indicating that our study will provide new, high resolution imaging of this area. Synthetic waveforms are simulated through a three-dimensional heterogeneous Earth model using a finite-difference wave propagation method with a grid spacing of 0.025º, which accurately reproduces Rayleigh waves at 15+ seconds. Following this, phase delays are measured between the synthetics and the data, sensitivity kernels are constructed using the scattering integral approach, and we invert using a sparse, least-squares method. Preliminary results show that slow velocities are present beneath both the WSB and ASB, possibly indicating oldmore »