**6.1 Key factors affecting induced seismicity**

As shown in **Figure 11** [54], the mechanism for inducing seismicity appears to be well known, that is, weakening pre-existing faults by increasing fluid pressure. The formation will release stored elastic strain energy when a fault slips, triggering seismicity. The fault will remain locked as long as the applied shear stress is less than the

**Figure 11.** *Schematic diagram of mechanisms for inducing seismicity [54].*

strength of the contact. The failure condition can be determined according to the effective stress principle and the Mohr-Coulomb criterion.

Theoretically, the increase of fluid pressure should be the direct reason for induced seismicity and it can be avoided by changing the injection rate and controlling the formation pressure to avoid induced seismicity. Based on the mechanism of induced seismicity, the possible reasons for seismic events caused by GCS are clarified [57–59].

