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SUMMARY:What small earthquakes can teach us about large earthquakes at cal
 dera ring faults - Tom Winder\, University of Iceland
DTSTART:20250224T140000Z
DTEND:20250224T150000Z
UID:TALK228850@talks.cam.ac.uk
CONTACT:ChuanChuan Lu
DESCRIPTION:Magnitude ~ 5 earthquakes are often observed at caldera volcan
 oes undergoing unrest. These earthquakes stand out in regional and telesei
 smic moment tensor catalogues for their shallow depths and non-double-coup
 le source mechanisms. Intriguingly\, the orientation of the moment tensor 
 (vertical-dilatational or vertical-compressional) appears to correlate wit
 h the stage of volcanic unrest (inflation building up to eruption\, or def
 lation as magma leaves the edifice)\, but we don’t yet have a general un
 derstanding of what source processes lead to their distinctive nature.\n \
 nIn this talk I will explore how local measurements of such earthquakes at
  Bárðarbunga caldera\, central Iceland\, can be used to investigate this
  further. Bárðarbunga has hosted the longest sequence of such anomalous 
 earthquakes observed at any volcano globally\, and in 2014-15 hosted a spe
 ctacular eruption that featured more than 70 of these Mw 5+ events over a 
 period of just 6 months. Analysis of detailed observations of seismicity a
 nd ground deformation delivered important new constraints on models of the
  caldera system and ring faults\, but also new questions. Since 2015 the e
 difice has been re-inflating\, accompanied by around 1-2 large earthquakes
  per year. We have sought to exploit this by supplementing the long-runnin
 g regional network with temporary dense deployments of seismometers above 
 the ice-filled caldera\, to provide further improved constraints on earthq
 uake locations and focal mechanisms. I will describe the 10’s of thousan
 ds of earthquakes we have located from these few months of data\, and the 
 new insights they provide into caldera ring fault seismicity at Bárðarbu
 nga.\n
LOCATION:Wolfson Lecture Theatre
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