Controlling Induced Earthquake Magnitude by Cycled Fluid Injection

The possibility of controlling induced earthquake magnitude through managed metering of water injection has yet to be rationalized. Mechanisms of reducing magnitudes of induced events through cycled fluid injection remain unclear. To explore such mechanisms and this possibility, we report experiments with water injection into laboratory faults. Water injection results in early triggering for both single and cycled injection. However, the maximum moment magnitude and total energy of the repeating induced earthquakes during cycled water injection are both lower than those of induced earthquakes induced with continuous injection and for natural earthquakes without water injection. Higher permeability of the host reduces the number of injection-induced earthquakes but increases their moment. With an increasing number of water injection cycles, both maximum moment and total energy decrease, particularly as permeability decreases, while the number of induced events increases. The moment magnitude of induced events can thereby be controlled through cycled fluid injection.