Towards a new standard for seismic moment tensor inversion containing 3-D earth structure uncertainty

Author:

Phạm T -S1ORCID,Tkalčić H1ORCID,Hu J1ORCID,Kim S2ORCID

Affiliation:

1. Research School of Earth Sciences, The Australian National University , Canberra, Acton ACT 0200 , Australia

2. Department of Earth and Environmental Sciences, Korea University , Seoul 02841 , Republic of Korea

Abstract

SUMMARY Moment tensor (MT) inversion is a classical geophysical inverse problem that infers a force-equivalent model of a seismic source from seismological observations. Like other inverse problems, the accuracy of the inversion depends on the reliability of the forward problem simulating waveforms from the source location through an Earth structural model. Apart from errors in data, the error in forward waveform simulation, also known as theory error, is a significant source of error contributing to the misfit function between the predicted and observed waveforms. Here, we set up numerical experiments to comprehensively probe the sensitivity of the linearized MT inversion to 3-D regional earth model errors, a known predominant factor of the theory error. Using the Monte Carlo method, we estimate the empirical structural covariance matrices to characterize the waveform mismatch due to the imperfect knowledge of Earth's structure. First, although the inversion accuracy deteriorates with increasing model errors, incorporating the structural covariance matrices into the misfit function improves the accuracy of inversion results for all theorized error distributions. Secondly, we propose a slightly modified form of the structural covariance matrix, which further enhances the inversion outcome. Lastly, as the true structural errors are likely spatially correlated, we highlight the importance of adequately treating the correlation into the MT inversion because of its significant impact on inversion. Overall, as a preliminary effort in quantifying 3-D structural errors on MT inversion, this study proves the computational feasibility by means of numerical experiments and will hopefully provide a way forward for future work on this topic.

Funder

Air Force Research Laboratory

Australian Research Council

National Computational Infrastructure

Australian Government

Publisher

Oxford University Press (OUP)

Reference56 articles.

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