Relation between filling of reservoirs and earthquakes

Abstract

From the Editors. The phenomenon of increase of seismic activity during the filling of several large reservoirs, observed in recent years [26], has raised a new complex problem in the hydraulic engineering field. This problem is especially timely for the Soviet hydraulic engineers in connection with the design and construction of several high-head hydraulic structures in seismic regions. It is evidently necessary to take into account in design the possibility of the development of seismicity caused by such activities. This problem is highly complex because of the fact that at the present time there are no clear concepts about the mechanism of the development of such earthquakes. The author of this article, which is being published for discussion, presents several considerations which, in his opinion, can explain the mechanism of earthquakes associated with reservoir construction. The author's pronouncements do not correspond always to the present-day level of geotectonics and seismology, but many of his ideas may be of interest and should lead to discussions of this important problem.Many cases of occurrence of seismic activity during the filling of large reservoirs in regions which had been previously considered as aseismic [8 and 18-22] have raised the problem of the study of the interrelation between these phenomena. This problem was discussed at the Ninth and Tenth International Congresses on Large Dams and has been included in the agenda for the llth Congress. A special group of experts from the UNESCO organization is engaged in the study of the problem of earthquakes connected with artificial reservoirs.Despite a large number of cases of induced seismicity, at the present time there is no clear concept about the mechanisms governing its development. On the other hand, similar characteristics of the "ordinary" 'earthquakes which occur during the filling of reservoirs as well as the occurrence of induced seismicity when water is pumped into deep holes provide reasons for examining more carefully the mechanism of the development of "ordinary" earthquakes from the standpoint of the role played by water in this process. A very characteristic concept on this problem was formulated by the well-known seismologist Rothe: "... The exact mechanism of the development of strong artificial earthquakes is incomprehensible, although it is clear that, just as in natural earthquakes, in this case there is in the weak zones a liberation of energy accumulated within a limited rock volume. Although the origin of natural earthquakes is not known, the relation between artificial earthquakes and the weight of the water is evident. It is hoped that the study of artificial earthquakes will help to solve the problem of the prediction of earthquakes in the general case" [19].According to current theories, the factors considered as the potential causes of earthquake development can have very complex interrelations. However, in the final analysis all of them lead to variations in the stress state of the rock masses in the earth's crust...

Current state and immediate problems of the mechanics of rock foundations of hydraulic structures

“…We can expect, for example, that a fracture running deep ir~to the mass in which the water is not in a hydraulically continuous state, after filling of the reservoir will become completely saturated in the course of time. This will lead to a marked increase of pressure on the wails of the fracture with the possibility of dangerous consequences [10]. Such a problem is solved rather simply with the use of the finite element method.…”