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SUMMARY:Axial Seamount as a unique laboratory to study how stress changes 
 affect earthquake occurrence - Yen Joe Tan\, Chinese University of Hong Ko
 ng
DTSTART:20201021T110000Z
DTEND:20201021T120000Z
UID:TALK151849@talks.cam.ac.uk
CONTACT:Tim Greenfield
DESCRIPTION:Studying how stress changes modulate earthquake occurrence can
  shed light on the earthquake nucleation process\, as well as the friction
 al property and stress state of natural faults. In this talk\, I will pres
 ent results from a seafloor observatory that was established on Axial Volc
 ano in 2015. We have set up a monitoring system that computes high-precisi
 on earthquake locations in near-real-time. During the first year of operat
 ion\, ~100\,000 earthquakes were located that delineated an outward-dippin
 g ring fault system in a 25 km³ block of crust. Since the fault system ex
 periences periodic tidal loading\, this represents a natural laboratory fo
 r us to study how earthquakes respond to stress perturbations. We find tha
 t the underlying magma chamber inflates and deflates in response to tidal 
 loading\, triggering normal faulting earthquakes during low tides and inhi
 biting them during high tides. The stress dependence of seismicity rate co
 nforms to triggering theory over the whole tidal stress range. There is no
  triggering stress threshold and stress shadowing is simply a continuous f
 unction of stress decrease. The rate-state friction parameter A is an orde
 r of magnitude smaller than laboratory measurements. We further find that 
 the earthquake b value is inversely correlated with tidal stress\, confirm
 ing the stress dependence of earthquake size distribution. 
LOCATION:ONLINE - Details to be sent by email
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