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Toward High-Frequency Three-Dimensional Green's Function Databases

Description: 

An effort is underway at national laboratories and universities to compute new 3D Green's functions. To inform choices for production Green’s function simulations, we present ~1 Hz comparisons between elastic solvers and preliminary 3D moment tensor inversions for 6 historical underground explosions.

Among the results of the comparisons, we show that, even with extremely conservative meshing, differences of practical significance can persist between finite-difference and finite-element synthetics. More subtly, source-dependent amplitude errors related to finer meshing requirements for shear relative to compressional waves can give rise to systematic biases, motivating detailed convergence checks.

Guided by the above, we computed finite-element Green's functions and corresponding moment tensors for the historical explosions. Our results show that meaningful patterns can persist in moment tensor uncertainty surfaces even when best-fitting moment tensor solutions become unreliable. For low-magnitude or sparsely-recorded seismic events, 3D Earth models may provide new source constraints different from the usual Rayleigh-wave radiation pattern constraints that tend to dominate 1D inversions, with implications for improved source-type estimation in particular.

Session: 3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling - I

Type: Oral

Date: 5/2/2024

Presentation Time: 08:45 AM (local time)

Presenting Author: Ryan

Student Presenter: No

Invited Presentation: 

Authors