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A High-Resolution Phase Velocity Inversion for the Crustal Structure of the Southeastern Us Using a Double-Sided Hankel Transform

Description: 

Understanding the Alleghenian orogeny and its influence on the tectonic evolution of Laurentia depends on understanding the structural relationship between the Suwannee and its adjacent terranes. Our study focuses on creating high-resolution phase velocity estimates of the entire southeastern US region with less non-uniqueness than that of current models and with more accurate locations and orientations of terranes to constrain passive margin formation.

Vertical component seismograms are used to model Empirical Green’s functions (EGF) to measure Rayleigh waves via cross-coherence computation for all possible station pairs from approximately 300 broadband seismic stations deployed during the EarthScope project. Because the noise source distribution is not uniform from all directions, the EGF is corrected for all noise sources along the Great Circle Path (GCP) between the virtual source and receiver pair. This has been done with the help of Double Optimized Multiple Signal Comparison (DOPMUSIC), where the significant number of noise sources for all possible frequency bands along the GCP is used to estimate the appropriate EGF.

DOPMUSIC produces Rayleigh waves with significantly higher SNR for all frequency bands than the classical Double Beamforming (DBF) approach. The estimated EGF is used to calculate phase velocity dispersion curves with the help of spatially-variable Hankel transform functions. Classical phase velocity estimation approaches lack uniqueness because of cycle-skipping while matching the phase. The classical Frequency-Bessel transform often contaminates the phase velocity estimates by spatial aliasing and bi-directional velocity scans. And in effect, several crossed dispersion curves were observed in the spectrogram. We use the Hankel function instead of the Bessel function on the causal and acausal part of the EGF separately, which addresses this problem. Phase velocity maps are then used to estimate 1-D shear wave velocity profiles for the entire region.

[PJ1]Need to insert a comment here about what is missing from, or wrong about, current models or ideas about the passive margin formation.

Session: Earth’s Structure From the Crust to the Core

Type: Oral

Date: 4/18/2023

Presentation Time: 08:45 AM (local time)

Presenting Author: Debajeet Barman

Student Presenter: Yes

Invited Presentation: 

Authors