Abstract

AbstractFault/fracture slip and seismicity caused by fluid injection are of major interest to subsurface science and engineering. However, some fundamental aspects of the temporal and spatial evolutions of induced seismicity remain unresolved. In this paper, we present the results of a laboratory injection‐induced shear test conducted on a rough granite fracture with concurrent acoustic emission (AE) monitoring. The results demonstrate a sequence of aseismic‐seismic‐aseismic fracture motion during fluid injection. It is observed that the temporal evolution of AE/microseismic activities was accompanied by the changes of slip velocity, stress drop, and friction coefficient. The seismic slip phase consists of three subphases, namely, a first quasi‐static slip, a dynamic slip, and a second quasi‐static slip. The dynamic slip occurred with an AE mainshock, simulating earthquake instability triggered by injection in deep crystalline rocks. In addition, slip heterogeneity controlled by the fracture surface roughness is directly evidenced by the spatially heterogeneous distribution of AE hypocenters and fracture surface topography.

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