Abstract: In recent years, reservoir induced earthquake (RIE) has drawn more and more attention in both the fields of seismology and computational geodynamics. Kariba reservoir is the world's largest reservoir by the volume of impoundment. After the impoundment of Kariba reservoir, there appeared seismicity around the reservoir region and an M6.1 earthquake happened in September 23, 1963, which is recognized as one of the four RIEs greater than M6.0 around the global. Therefore, it is a good example for quantitative assessment of the stress field changes induced by the impoundment of the large reservoir and investigation of the magnitude of stress changes that can trigger reservoir seismic activities. Adopting analytical solution and finite element method, we first calculated simultaneously the changes of elastic stress and undrained pore pressure induced by water load. After that, the drained pore pressure after the impoundment, which varies with the respect of time, was also introduced. Our primary results reveal that reservoir impoundment increases pore pressure and coulomb stress changes at the hypocenter of this major event. The value of coulomb failure stress changes is around 0.03~0.17 MPa and the pore pressure is about 0.015~0.22 MPa.

Key words: Reservoir triggered earthquake, Stress field, Pore pressure, Kariba reservoir