Factors Controlling the Occurrence of Reservoir-Induced Seismicity

Reservoir-induced seismicity (RIS) is defined as the failure of a pre-existing fault due to reservoir impoundment or water level fluctuations. 127 RIS cases have been recorded around the world, with four events of M > 6. RIS is triggered by a complex interaction between a number of factors including reservoir size, stress regime, hydrogeological condition and reservoir-filling history. Using statistical evaluation of worldwide data the relationships among these factors are investigated. The occurrence of RIS shows a strong correlation with reservoir size, faulting regimes, rock types and background seismicity. However these factors alone are certainly not necessary or sufficient conditions for the triggering of RIS. As the interactions between water movement and geology can be significantly complex, a detailed study on the Xinfengjiang reservoir is presented. Examination of fault location, orientation and permeability structure indicate that the NNW Shijiao-Xingang-Baitian fault is responsible for the majority of seismic events, including the M(s)6.1 mainshock. The hydrogeological conditions causing RIS are discussed.