We discuss characteristics of geomechanically modeled microseismicity in a scenario of hydraulic fracture activation of a preexisting fault. This modeling example represents a geomechanical tutorial of the fault activation in a relatively simple scenario, which may be of use when interpreting microseismic imaging and induced seismicity field data. The model confirms the expected result of induced shear slip when the hydraulic fracture intersects the fault. However, a subtle asymmetry in fault slip and associated onset of the microseismicity occurs due to stress shadowing around the hydraulic fracture. Although the modeled microseismicity along the fault is predominantly associated with a shear mechanism, localized dilation of the fault introduces a relatively small fault-opening component for small-magnitude microseismicity. Finally, episodic clusters of microseismicity were found as the area of fault activation grew. This was associated with an initial slip event and subsequent redistributions on localized segments of the fault.

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