Evolution of Pulverized Fault Zone Rocks by Dynamic Tensile Loading During Successive Earthquakes

Abstract

Large strike-slip faults experience numerous earthquakes during which transient tensile and compressive mean normal stress perturbations travel along opposing sides of the fault. Research exploring dynamic rock fracture through multiple earthquake cycles has focused predominantly on transient compressive loading, but little is known about off-fault damage development due to successive tensile loading. We investigate damage accumulation by transient tensile loading over multiple earthquake cycles using a modified sample configuration for uniaxial compressive loading apparatuses consisting of a Westerly granite rock disk bonded to two lead disks. We show that fracture density increases during each successive loading cycle, and pulverized rock can be produced under tension at strain rates as low as 10−3 s−1. Therefore, pulverized rock can form at low strain rates, and its texture and extent may be controlled by the size of the coseismic tensile stress perturbation and the number of slip events on the fault.