The possible earthquake issue due to Three Gorges reservoir has been emphasized by the government for a long time, and extensive researches have been made on the issue involved in the rock, geologic structure, osmosis, etc. A 300~800 m deep-hole earth stress observation is carried out at dam and reservoir site and the earthquake intensive observation is made on some fracture zones around the dam. According to the researches, the geologic structure is stable, and has no geological background for a future heavy earthquake.
Even after the water rises, though we can not exclude the possibility of any earthquake due to the reservoir, the possible max earthquake intensity will not exceed class VI, and will not influence most of the project buildings that are designed on the basis of a earthquake of class VII.
The earthquake monitoring indicates that earthquake activities may increase after the reservoir operates, but that of higher than class II is little, and have no damages to the reservoir area, nor to the dam that is designed to be able to withstand Class VII earthquake.