SVIBOR - Project code: 2-11-004


Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69


SVIBOR - Collecting Data on Projects in Croatia

Project code: 2-11-004


Main researcher: STOJIĆ, PETAR (92774)

Type of research: basic
Duration from: 06/01/91. to 12/31/93.

Papers on project (total): 0
Institution name: Građevinski fakultet, Split (83)
City: 21000 - Split, Croatia
Phone: 385 (0)21 52 33 33
Fax: 385 (0)21 52 41 62

Summary: INFLUENCE OF MAN MADE LAKES ON EARTHQUAKS The phenomenon of earthquake by water storage reservoirs was discovered before the Second World War on the Marathon dam in Greece - l930, on the Qued Fodda dam in Algiers - 1933 and on the Hoover dam (Boulder) in USA - 1935. The public all over the world was the first time warned of that danger by the French Committee for High Dams in 1967. The same year the Committee for High Dams of former Yugoslavia declered that three seismographs were installed on the Grančarevo dam (1965) in order to study the eartquakes caused by water storage reservoir in karst areas. A number of research works carried out in various countries have indicated that man made lake might be cause of seismic activity. Seismic movements of the earth's crust on large areas, or the macro- seismic earthquakes, are an important factor to be taken into consideration in selecting a dam site in design of dams. However, in large region of equal degree of macro-seismic activity, areas may have differences in local seismic characteristics. Such a local micro-seismic activity has often neglected in investigations, design and constuction. Large dams and man made lakes are considered as "passive factors" in terrain movements caused bu natural forces. Recent informations indicate that large dams and storage reservoirs may cause earthquakes of both the macro-seismic and micro-seismic nature. In such seismic movements the dam and the reservoir are "active factors" which influence the seismic processes in the earth's crust. Consequently, two types of earthquakes have to be distinguished, as the two variants of seismic activity, namely the seismic activity influenced by naturel forces, and seismic activity influenced by storage reservoirs. Significant experiences were accumulated in many countries. Systematic observations and investigation of eventual effects of storage reservoir on induced sesmicity was initiated with construction of the system of hydroelectric power plants on the Trebišnjica River, one of the largest subterranean karst river in Europe. It sinks undergound in Popovo Polje after a course of about 100 km, with outflowing either close to the Adriatic Sea or at the Neretva River. By creating the reservoir (V = 1,3 *10**9 m3) the Trebišnjica River Springs were flooded by 77 m. The construction of Grančarevo Arch Dam ( 123 m high) started in 1960., foundation excavations initiated in 1964. Special highly sensitive seismographs have be put in operation on Febuary 6, 1965. Filling of the reservoir began on November 1, 1967. Filling of the reservoir causes changes in seismic activity evenat great distances from the reservoir (75 km). The seismic activity measured by the number and total released energy of eartquakes increased after start of filling of the reservoir. A noticeable increase in seismic activity has occured for the reservoir depths of over 6o m. During the initial cycles of loading and unloading of the reservoir, the seismic activity is evidently affected by reservoir levels. The correlation coefficient (linear regression) between the monthly number of earthquakes of each hudrological year (1st November past year - 31st October next year) and correspoding mean monthly water height in the reservoir indicate strong association during first four cycles of reservoir loading and unloading (r = 0,82 - 0,90). According to the records detected with instruments, for the period after filling the reservoir 11.1.1967. - 10.31.1990., were 16.751 earthquakes with released energy E =5,3*10**10 J. The strongest earthquake within the region around the reservoir happened October 3, 1979. with magnitude M=4,9. With increase of the earthquake epicenter distance from the dam the energy released also increase. The released energy is inversely proportional to the number of eartquakes; the higher the number of earthquakes the less energy they release.

Keywords: dams, man made lakes, storage reservoirs, filling, induced seismicity, earthquakes, released energy, correllation, mathematical statistics, probability, karst areas, Grančarevo dam.

Research goals: According the collected data for 23 hidrological year are calculated correlation coefficients from number of earthquakes and corresponding monthly water lavels. Filling of the reservoir causes changes in induced seismicity.


  1. Name of institution: HRVATSKA ELEKTROPRIVREDA - suradnik: Istraživać LALIĆ RODOLJUB
    Type of institution: Economical/Production
    Type of cooperation: Joint project
    City: 21000 - Split, Croatia

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Last update: 10/09/95