Title: Global centroid moment tensor solutions in a heterogeneous earth: the CMT3D catalogue

Abstract

SUMMARY For over 40 yr, the global centroid-moment tensor (GCMT) project has determined location and source parameters for globally recorded earthquakes larger than magnitude 5.0. The GCMT database remains a trusted staple for the geophysical community. Its point-source moment-tensor solutions are the result of inversions that model long-period observed seismic waveforms via normal-mode summation for a 1-D reference earth model, augmented by path corrections to capture 3-D variations in surface wave phase speeds, and to account for crustal structure. While this methodology remains essentially unchanged for the ongoing GCMT catalogue, source inversions based on waveform modelling in low-resolution 3-D earth models have revealed small but persistent biases in the standard modelling approach. Keeping pace with the increased capacity and demands of global tomography requires a revised catalogue of centroid-moment tensors (CMT), automatically and reproducibly computed using Green's functions from a state-of-the-art 3-D earth model. In this paper, we modify the current procedure for the full-waveform inversion of seismic traces for the six moment-tensor parameters, centroid latitude, longitude, depth and centroid time of global earthquakes. We take the GCMT solutions as a point of departure but update them to account for the effects of a heterogeneous earth, using the global 3-Dmore » wave speed model GLAD-M25. We generate synthetic seismograms from Green's functions computed by the spectral-element method in the 3-D model, select observed seismic data and remove their instrument response, process synthetic and observed data, select segments of observed and synthetic data based on similarity, and invert for new model parameters of the earthquake’s centroid location, time and moment tensor. The events in our new, preliminary database containing 9382 global event solutions, called CMT3D for ‘3-D centroid-moment tensors’, are on average 4 km shallower, about 1 s earlier, about 5 per cent larger in scalar moment, and more double-couple in nature than in the GCMT catalogue. We discuss in detail the geographical and statistical distributions of the updated solutions, and place them in the context of earlier work. We plan to disseminate our CMT3D solutions via the online ShakeMovie platform.« less

Authors:

Sawade, Lucas ;

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• Search DOE PAGES for ORCID "0000-0003-4501-2665"

Beller, Stephen; Lei, Wenjie; Tromp, Jeroen

• Search DOE PAGES for author "Tromp, Jeroen"
• Search DOE PAGES for ORCID "0000-0002-2742-8299"

Publication Date:

Sat Jul 23 00:00:00 EDT 2022

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)

Sponsoring Org.:

USDOE Office of Science (SC); National Science Foundation (NSF)

OSTI Identifier:

1885174

Alternate Identifier(s):

OSTI ID: 1982496

Grant/Contract Number:  

AC05-00OR22725; 1644826

Resource Type:

Published Article

Journal Name:

Geophysical Journal International

Additional Journal Information:

Journal Name: Geophysical Journal International Journal Volume: 231 Journal Issue: 3; Journal ID: ISSN 0956-540X

Publisher:

Oxford University Press

Country of Publication:

United Kingdom

Language:

English

Subject:

58 GEOSCIENCES; Waveform inversion; Computational seismology; Seismicity and tectonics