Repeated rupture of persistent fault zone asperities: structure and variability of large earthquakes at the Kermadec subduction zone

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• Karen Lythgoe, University of Edinburgh
• Wednesday 07 February 2024, 16:00-17:00
• Wolfson Lecture Theatre.

If you have a question about this talk, please contact Janneke de Laat.

Repeated slip on the same section of fault with earthquakes of similar size and mechanism, are so-called ‘characteristic earthquakes’. Such fault patches may be created by the existence of persistent asperities (isolated high strength regions) on the fault interface. However, many aspects of this apparent repeating behaviour are unclear – including i) how variable large events on the same fault segment are, ii) whether the same asperities are truly re-rupturing each time and iii) what factors limit slip to a particular region.

Rare occurrences of a complete earthquake cycle within the time of modern instrumentation are at rapidly slipping faults, particularly old oceanic subduction zones, such as Tonga-Kermadec. Here, the same portion of the plate interface has ruptured in M8+ earthquakes in 1917, 1976 and 2021. In this talk, I’ll present detailed observations of these earthquakes and show that although the same asperities likely re-ruptured in 1976 and 2021, the detailed slip distribution is different. Additionally, all earthquakes occur in an isolated area of the megathrust, which is bounded by changes in the lithospheric structure of the overriding plate. This high-seismicity region is coincident with an isolated forearc sedimentary basin, possibly formed by basal erosion related to seismogenesis, suggesting that seismic slip has persisted in this isolated area for several million years. I conclude that stress heterogeneity within this bounded seismogenic zone is long-lived and has produced a rich spectrum of earthquake ruptures.

This talk is part of the Bullard Laboratories Wednesday Seminars series.

This talk is included in these lists:

• Bullard Laboratories Wednesday Seminars
• Department of Earth Sciences seminars
• Wolfson Lecture Theatre

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