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SUMMARY:Permeability of fault zones and how it changes over time - Profess
 or Emily E. Brodsky\, University of California\, Santa Cruz
DTSTART:20150521T110000Z
DTEND:20150521T120000Z
UID:TALK58677@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Permeability is commonly assumed to be a geometrically control
 led constant that is fixed over human timescales. However\, continuous mea
 surements of permeability from tidal responses reveal that the apparent pe
 rmeability can change significantly over time.  Seismic waves from regiona
 l earthquakes can increase the permeability by factors of up to 3-4 and th
 e permeability can recover slowly over a period of years. Permeability cha
 nge is correlated to peak ground motion and we can recreate this fundament
 al observation with laboratory experiments.  We have demonstrated through 
 image analysis and variations in adhesive behavior with the ionic strength
  of the fluid that the mechanism of these experimental permeability enhanc
 ements is the clearing of clogged fractures. The fluid velocity during the
  oscillations is the best predictor of the resultant permeability enhancem
 ent. Transient permeability effects are particularly important in fault zo
 nes where the hydrogeology is coupled to the strength of the fault. For in
 stance\, we have directly measured the permeability recovery within a majo
 r fault following the 2008 M7.9 Wenchuan earthquake and showed that the ev
 olution of the system continues for years after the mainshock.
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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