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SUMMARY:Energy partitioning and shear resistance evolution during earthqua
 ke sequences in experiments with simulated quartz gouge - Daniel Faulkner\
 , University of Liverpool
DTSTART:20250122T140000Z
DTEND:20250122T150000Z
UID:TALK227029@talks.cam.ac.uk
CONTACT:Adriano Gualandi
DESCRIPTION:During their lifetime\, seismogenic faults will experience num
 erous earthquakes\, with each event imparting damage onto the rocks that c
 omprise the fault core and the surrounding country rock. The partition of 
 energy between creating new fracture surface area\, heat production\, and 
 other co-seismic processes is not well constrained and will evolve with mu
 ltiple events on a fault. This evolution will have important implications 
 for the rupture breakdown energetics in subsequent events\, and also the f
 luid flow properties of the fault (i.e.\, by altering fault permeability).
  We investigate experimentally the evolution of fault gouge properties dur
 ing multiple seismic slip events by performing a series of high-velocity s
 lip-pulse experiments on simulated quartz gouge. The quartz gouge layers a
 re repeatedly sheared (up to 25 slip pulses) in a high-velocity rotary she
 ar apparatus at a maximum sliding velocity of 1 m/s for a total displaceme
 nt of 0.8 m during each slip pulse. A normal stress of 10 MPa is applied t
 o the gouge layer\, while the pore fluid pressure is controlled at a const
 ant value of 5 MPa during each experiment (i.e.\, effective normal stress 
 = 5 MPa). During the sequences of high-velocity slip pulses we find that t
 he area under the shear stress – displacement curve (sometimes called th
 e breakdown energy) of each pulse systematically increases until a steady-
 state is reached after around 10 slip pulses\, after which it remains cons
 tant for each subsequent slip pulse. The development of mechanical behavio
 ur is associated with the evolution of gouge microstructure. During the fi
 rst 10 slip pulses\, the gouge grain size systematically reduces during ea
 ch pulse as a result of the formation of submicron-sized particles\, leadi
 ng to an increase in the gouge surface area. However\, after the first 10 
 slip pulses\, the gouge microstructure reaches a steady-state and the goug
 e grain size and surface area remain approximately constant during subsequ
 ent slip pulses. Our results provide new insights on the evolution of faul
 t gouge properties during multiple earthquake sequences and the implicatio
 ns this has for the partitioning of the rupture energy budget during futur
 e earthquake events.
LOCATION:Wolfson Lecture Theatre
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