Romania is one of Europe's most seismically active regions, together with other Balkan and Mediterranean countries - Bulgaria, Turkey, Greece, the former Yugoslavia and Italy.   The seismicity of Romania is mainly due to activity from within the Vrancea region: the source zone is at an intermediate depth (about 60 to 200 km), and it delivers more than 95% of the whole seismic energy for the country.  This source zone directly affects about half the territory of Romania, producing high intensity earthquakes.

The earthquakes of 10 November 1940 (M=7.4), and of 4 March 1977 (M=7.2) were the largest in this century.  It is believed that the great earthquake of 1802 may have reached M=7.7.  The upper limit of magnitudes for Vrancea earthquakes is in the region of M=8.0.  Other source zones (in the Fagaras Mountains and the Banat) are crustal, and generate lower magnitudes - seldom exceeding M=6.0;  the resultant earthquakes tend to be localised.

Seismological information for Vrancea earthquakes is plentiful, primarily due to their high frequency of occurrence.  Return periods are in the region of 6 years for M=6, of 30 years for M=7, of 120 years for M=7.5.

Numerous accelerographic records were obtained during the earthquakes of 30 August 1986 (M=7.0), 30 May 1990 (M=6.7) and 31 May 1990 (M=6.1).  These data made a major contribution to the advancement of our knowledge.  The 1977 earthquake, which generated intensities in the range I=VIII MSK in a number of urban areas, provided extensive information on the performance of buildings and other artifacts.   Vulnerability characteristics were also derived for several categories of buildings.

Losses during the 1977 earthquake were considerable: about 2,000 lives were lost, some 30,000 apartments were heavily damaged or destroyed, and more than thirty major buildings collapsed - most of them in Bucharest.  This earthquake had a huge economic impact:   according to some estimates (which now seem rather low), the loss exceeded 2000 million US dollars.  The 1977 earthquake drew attention to the high vulnerability of unprotected buildings, but it also highlighted the efficiency of modern earthquake engineering design rules.  While 7% of the (approximately 400) pre-war high-rise buildings in Bucharest collapsed, only one in ten thousand apartments designed to resist earthquakes was destroyed.  If one considers the whole area affected by intensities of I=VII or more, the incidence of collapsed apartments is three-to-four times lower; this is a very good record as compared with world-wide experience.

In spite of the encouraging outcome of the 1977 earthquake, professionals are conscious of the seismic risk affecting the country, especially in areas subjected to earthquakes from the Vrancea region.  This risk is high, especially for the older building stock.  

Problems are also created by industrial facilities with the potential for heavy pollution;  by some large dams, and by various infrastructure components; studies are under way to control and reduce these risks.  A number of regulations were recently endorsed in this connection, but extensive work still needs to be undertaken, and corresponding resources are to be provided.

Text by Horea Sandi.