Based on a large amount of microseismic informations and hundreds of rockbursts with different intensities occurring in the deep diversion tunnels of Jinping II hydropower station excavated with drill-and-blast method and tunnel boring machine (TBM)

the energy release processes of immediate rockbursts with different excavation methods are compared; and energy distribution of microseismic events are analyzed by fractal theory. The achieved results are as follows: (1) Damage of rock mass are gathering and expanding in the processes of immediate rockbursts. (2) Elastic potential energy which stored within the rock mass has different ways of release with different excavation methods. (3) The energy fractal dimension values would increase continuously before the rockburst happens and they totally increase to a critical value when the rockburst approaches during drill-and-blast method excavation. (4) The energy fractal dimension values in TBM excavation which is bigger than that in drill-and-blast method can describe the mild and moderate rockbursts of the working face.