关键词: 水库地震, 库仑应力, 孔隙弹性介质理论, 岩溶, 重力荷载, 断层产状

Abstract: So far,although many reservoirs have been built,few of them have triggered seismicity.In order to study the mechanism of triggered seismicity so as to provide useful reference data for site selection of dams,we analyze the effects of hydro-geological structures and gravity loads in reservoir areas,and draw some conclusions:1)Rapid-response type seismicity may occur when there are some abandoned mines or karst caves;2)Based on the results of numerical calculation,Coulomb stress on different faults changes differently when the gravity load of the reservoir increases or decreases.The calculation results change with the stress field,the fault parameters and the relative position of the fault and reservoir.When the reservoir is on the down-thrown block and the fault dip is large,the fault may be more unstable because of the gravity load.In this case,Coulomb stress may increase locally on normal dip-slip faults,but on whole reverse dip-slip fault.Under the same fault occurrences,the Coulomb stress change of a normal dip-slip fault is larger than that of the reverse dip-slip fault.When the coefficient of friction is 0.6,the quantity of Coulomb stress change induced by gravity load is about 1/4 as much as that induced by pore water pressure in the fracture of the saturated karst cave.So,more attention should be paid to pore water pressure in the fracture.

Key words: reservoir-induced earthquake, Coulomb stress, Biot theory, limestone karst, gravity load, fault occurrence