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Iterative Global 3D Centroid Moment Tensor Inversions Using Stored Global Green Functions From Glad-M25

Description: 

Though the synthetic seismograms used for Global CMT inversion are based on modern 3D Earth models, their accuracy is limited by the validity of the path-average approximation for mode summation and surface-wave ray theory. Inaccurate computation of ground motion amplitude and polarization, and other effects that are not modeled, may bias inverted earthquake parameters. Synthetic seismograms of higher accuracy will improve the determination of seismic sources in the CMT analysis, and reduce concerns about this source of uncertainty. However, traditional forward computation of 3D synthetic seismograms for iterative source inversion remains computationally prohibitive. The calculation of a strain-tensor database has recently been implemented for the spectral-element solver SPECFEM3D (Ding et al., 2020), based on theory from previous work for regional inversion of seismograms for earthquake parameters (Zhao et al., 2006). The main barriers to a global database of Green functions have been storage capacity, I/O, and computation speed. We show that subselecting necessary elements can efficiently overcome these issues when storing reciprocal wavefields for 183 stations of the Global Seismographic Network. Here, we apply this framework of Green Function storage to the set of GCMT solutions used for the CMT3D catalog Sawade et al. (2021) and compare GCMT, CMT3D, and CMT3D+ solutions, the latter of which are iteratively inverted for moment tensor and centroid location and time until converged.

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

Type: Oral

Date: 5/2/2024

Presentation Time: 09:00 AM (local time)

Presenting Author: Lucas

Student Presenter: Yes

Invited Presentation: 

Authors