Seismo Lab Seminar

During their lifetime, seismogenic faults will experience numerous earthquakes, with each event imparting damage onto the rocks that comprise 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 multiple events on a fault. We investigate experimentally the evolution of fault gouge properties by performing a series of high-velocity slip-event experiments on simulated quartz gouge. The quartz gouge layers are repeatedly sheared (up to 25 slip events) in a high-velocity rotary shear apparatus at a maximum sliding velocity of 1 m/s for a total displacement of 0.8 m during each slip event. A normal stress of 10 MPa is applied to the gouge layer, while the pore fluid pressure is controlled at a constant value of 5 MPa during each experiment (i.e., effective normal stress = 5 MPa). During the sequences of high-velocity slip events we find that the area under the shear stress – displacement curve of each event systematically increases until a steady-state is reached after around 10 slip events, after which it remains constant for each subsequent slip event. The development of mechanical behaviour is associated with the evolution of gouge microstructure. During the first 10 slip events, the gouge grain size systematically reduces with the development of a power law particle size distribution, and an increase in the gouge surface area. After the first 10 slip events, the gouge microstructure reaches a steady-state and the gouge grain size and surface area remain approximately constant during subsequent slip events. Our results provide new insights on the evolution of fault gouge properties during multiple earthquake sequences and the implications this has for the partitioning of the rupture energy budget during future earthquake events.

For more information, please contact Seismo Lab Seminar Committee by phone at 626-395-6919 or by email at [email protected].