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SUMMARY:Repeated rupture of persistent fault zone asperities: structure an
 d variability of large earthquakes at the Kermadec subduction zone - Karen
  Lythgoe\, University of Edinburgh
DTSTART:20240207T160000Z
DTEND:20240207T170000Z
UID:TALK211252@talks.cam.ac.uk
CONTACT:Janneke de Laat
DESCRIPTION:\n\nRepeated slip on the same section of fault with earthquake
 s of similar size and mechanism\, are so-called ‘characteristic earthqua
 kes’. Such fault patches may be created by the existence of persistent a
 sperities (isolated high strength regions) on the fault interface. However
 \, many aspects of this apparent repeating behaviour are unclear – inclu
 ding i) how variable large events on the same fault segment are\, ii) whet
 her the same asperities are truly re-rupturing each time and iii) what fac
 tors limit slip to a particular region. \n\n \n\nRare occurrences of a com
 plete earthquake cycle within the time of modern instrumentation are at ra
 pidly slipping faults\, particularly old oceanic subduction zones\, such a
 s Tonga-Kermadec. Here\, the same portion of the plate interface has ruptu
 red in M8+ earthquakes in 1917\, 1976 and 2021. In this talk\, I’ll pres
 ent detailed observations of these earthquakes and show that although the 
 same asperities likely re-ruptured in 1976 and 2021\, the detailed slip di
 stribution is different. Additionally\, all earthquakes occur in an isolat
 ed area of the megathrust\, which is bounded by changes in the lithospheri
 c structure of the overriding plate. This high-seismicity region is coinci
 dent with an isolated forearc sedimentary basin\, possibly formed by basal
  erosion related to seismogenesis\, suggesting that seismic slip has persi
 sted in this isolated area for several million years. I conclude that stre
 ss heterogeneity within this bounded seismogenic zone is long-lived and ha
 s produced a rich spectrum of earthquake ruptures.
LOCATION:Wolfson Lecture Theatre
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