Engineering geological conditions in the Sofia Kettle and consequences from the earthquakes

Pages: 
pp. 117-121
Abstract: 

The historical review of the seismic activity shows that strong earthquakes with destructive effects took place in the Sofia kettle. There are data for the display of sufficiently powerful seismic events in the Sofia zone that had been reflected in historical documents as early as in the XV century. Four strong earthquakes occurred in this region during the period from the beginning of the XIX century till now that caused significant damages, the most powerful one being in 1858 (intensity of IX degree according to the MSK-64 scale and magnitude of about 6.5-7.0).
   According to the seismic zoning of Bulgaria for a period longer than 1000 years and average engineering geological conditions, the kettle falls entirely within a region with expected intensity of IX degree according to the MSK-64 scale with a seismic coefficient K = 0.27 (Boncev et aI., 1982; Norms for ..., 1987).
   The engineering geological characteristics of the Sofia kettle are the basis for determining the influence of the soil conditions on the effects of the seismic activity. Complex geologicalgeophysical investigations were carried out in the Sofia kettle during the period 1967-1970 in connection with the seismic microzoning of the territory of the Sofia City and the Sofia basin. On the basis of the engineering geological studies and the micro-seismic investigations (Petkov, Christoskov, 1965; Demirev et aI., 1971; Petrov, Iliev, 1971), the first attempts for preliminary seismic micro-zoning of the Sofia City and its surroundings were made, which were applied in practice too. The coefficient of variation of the seismic intensity is calculated according to the formula of Medvedev, the parameters of the monzonites and syenites of the Vitosha pluton being considered as reference ones. The values of this coefficient reach up to 3, and for the most unfavorable ground conditions - even to 3.5.

VOLUME 32 (2-4)/December 2002 110th Anniversary of Acad. Prof. Strashimir Dimitrov; XVII Congress of the Carpathian-Balkan Geological Association

Geologica Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev St., bl. 24, 1113 Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Akad. G. Bonchev Str., block 24
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Akad. G. Bonchev Str., block 24
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Akad. G. Bonchev Str., block 24
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Akad. G. Bonchev Str., block 24
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Akad. G. Bonchev Str., block 24
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Akad. G. Bonchev Str., block 24
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Akad. G. Bonchev Str., block 24

Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev str. Bl. 24

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia

Geological Institute, Bulgarian Academy of Sciences,Sofia 1113, Bulgaria, Acad. G. Bonchev str, bl. 24
|
Geological Institute, Bulgarian Academy of Sciences,Sofia 1113, Bulgaria, Acad. G. Bonchev str, bl. 24
|
Earth Science Section of the Uviversity of Geneva, 13, rue des Maraîchers, 1211 Geneva 4, Switzerland
|
Earth Science Section of the Uviversity of Geneva, 13, rue des Maraîchers, 1211 Geneva 4, Switzerland

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

Geological Institute BAS, Acad. G. Bonchev Str., Bl. 24 1113 Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
|
Sofia University "Sv. Kliment Ohridski", 1504 Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia
|
Sofia University "Sv. Kliment Ohridski", Tsar Osvobodilel Blvd, 15, 1000 Sofia
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia

Geological institute, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria
|
Geological institute, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria
|
Geological institute, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria
|
University of Mining and Geology "Sv. Ivan Rilski", 1700, Sofia

Geological institute, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia
|
Institute of Geochemistry, Siberian branch of the Russian Academy of Sciences, P.O.B. 4019, 664033 Irkutsk
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia
|
Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia

Geological Institute, Bulgarian Academy of Sciences, Sofia, 1113
|
Geological Institute, Bulgarian Academy of Sciences, Sofia, 1113
|
Geological Institute, Bulgarian Academy of Sciences, Sofia, 1113
|
Geological Institute, Bulgarian Academy of Sciences, Sofia, 1113
|
Geological Institute, Bulgarian Academy of Sciences, Sofia, 1113
|
Geological Institute, Bulgarian Academy of Sciences, Sofia, 1113

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia

Geological Institute, Bulgarian Academy of Sciences, Sofia, 1113

Geological Institute, Bulgarian Academy of Sciences

Geological Institute, BAS, Acad. G. Bonchev Street Bl. 24, 1113 Sofia, Bulgaria

Geological Institute of BAS, 24 Acad. G. Bonchev Sir., BG - 1113 Sofia
|
Geological Institute of BAS, 24 Acad. G. Bonchev Sir., BG - 1113 Sofia
|
Geological Institute of BAS, 24 Acad. G. Bonchev Sir., BG - 1113 Sofia

Geological Institute at the Bulgarian Academy of Sciences, Acad. G. Bonchev Str., 1113 Sofia, Bulgaria
|
Geological Institute at the Bulgarian Academy of Sciences, Acad. G. Bonchev Str., 1113 Sofia, Bulgaria
|
Geological Institute at the Bulgarian Academy of Sciences, Acad. G. Bonchev Str., 1113 Sofia, Bulgaria

University of Mining and Geology, Studentski grad, Sofia, 1100, Bulgaria
|
Geological Institute of Romania, Caransebes Str. No 1, Bucharest, RO-78344, Romania
|
University of Belgrade, Dusina 7, Belgrad, 11000, Yugoslavia
|
Geological Institute of Romania, Caransebes Str. No 1, Bucharest, RO-78344, Romania

Geological Institute at Bulgarian Academy of Sciences, Sofia 1113

Sofia University "Sv. Kl. Ohridski", Department of Geology and Palaeontology, 1504 Sofia