Abstract

Three reservoirs that are located in Koyna, India; Nurek, Tajikistan; and Aswan, Egypt are well‐documented cases of triggered earthquakes, each one having a recorded time series of seismicity and water levels that extend for more than 30 yrs. The geological setting, regional tectonics, modes of reservoir utilization, and the characteristics of reservoir seismicity interaction are distinctly different in each of these three cases. Similarities and differences between these three cases point to regional and local geological and hydrological structures, as well as the rate of changes in reservoir water level, as important factors controlling the presence and timing of triggered seismicity. In a manner that is similar to the influence of rate of fluid injection on injection‐related seismicity, the rate of change in reservoir water level has a significant influence on whether or not reservoir triggered seismicity occurs. The significant annual increase in water level, as well as the accompanying high rates of rise in the water level, may be important in sustaining the exceptionally long sequences of earthquakes at Nurek and especially at Koyna. In addition to the rate of filling being a determining factor in whether or not earthquakes are triggered, changes in the rate of filling may influence the time of occurrence of individual earthquakes.

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