Published February 2024 | Published
Journal Article Open

Finite source properties of large strike-slip earthquakes

  • 1. ROR icon California Institute of Technology

Abstract

Earthquake ruptures are complex physical processes that may vary with the structure and tectonics of the region in which they occur. Characterizing the factors controlling this variability would provide fundamental constraints on the physics of earthquakes and faults. We investigate this by determining finite source properties from second moments of the stress glut for a global data set of large strike-slip earthquakes. Our approach uses a Bayesian inverse formulation with teleseismic body and surface waves, which yields a low-dimensional probabilistic description of rupture properties including the spatial deviation, directivity and temporal deviation of the source. This technique is useful for comparing events because it makes only minor geometric constraints, avoids bias due to rupture velocity parametrization and yields a full ensemble of possible solutions given the uncertainties of the data. We apply this framework to all great strike-slip earthquakes of the past three decades, and we use the resultant second moments to compare source quantities like directivity ratio, rectilinearity, average moment density and vertical deviation. We find that most strike-slip earthquakes have a large component of unilateral directivity, and many of these earthquakes show a mixture of unilateral and bilateral behaviour. We notice that oceanic intraplate earthquakes usually rupture a much larger width of the seismogenic zone than other strike-slip earthquakes, suggesting these earthquakes may often breach the expected thermal boundary for oceanic ruptures. We also use these second moments to resolve nodal plane ambiguity for the large oceanic intraplate earthquakes and find that the rupture orientation is usually unaligned with encompassing fossil fracture zones.

Copyright and License

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

Acknowledgement

This work was partially funded by the National Science Foundation’s Graduate Research Fellowship Program (GRFP) with grant number DGE-1745301. The authors would like to thank Dr Jeffrey McGuire and an anonymous reviewer for their insightful comments which greatly improved this paper and the editor Dr Sidao Ni for facilitating the review process. The authors would like to thank Dr Théa Ragon for providing very useful suggestions regarding the uncertainties of fault slip distributions. The authors would also like to thank Dr Joann Stock for her insightful comments regarding intraplate oceanic ruptures.

Funding

This work was partially funded by the National Science Foundation’s Graduate Research Fellowship Program (GRFP) with grant number DGE-1745301.

Data Availability

The map shown in Fig. 1 was created using The Generic Mapping Tools (GMT), version 6 (Wessel et al2019), which is available at https://www.generic-mapping-tools.org/. The centroid moment tensor solutions used in this study are from the Global Centroid Moment Tensor (gCMT) catalogue (Ekström et al2012) which is accessible online at https://www.globalcmt.org/. The theoretical Green’s functions were computed using Salvus (Afanasiev et al2019), which is available at https://mondaic.com/. The waveform data in this study are from the Global Seismographic Network operated by both the Albuquerque Seismological Laboratory (IU: IRIS/USGS; https://doi.org/10.7914/SN/IU) (Albuquerque Seismological Laboratory (ASL)/USGS 1988) and the Scripps Institution of Oceanography (II: IRIS/IDA; https://doi.org/10.7914/SN/II) (Scripps Institution Of Oceanography 1986). These waveforms may be accessed through the IRIS Data Management Center (DMC).

Supplemental Material

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Additional details

Created:
January 24, 2025
Modified:
January 24, 2025