Distant Deep Earthquake Impact on Seismic Hazard in Serbia

Slavica Radovanović

Seismological Survey of Serbia

NATO SfP 984374 | Improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries

2nd PROJECT WORKSHOP

Vrancea earthquakesSeismic waves generated from the Vrancea seismoactive

zone are of great interest not only for Romania, but also for the neighboring countries due to their social and economical impact on these territories.

Since 1900, the maximal seismic intensity registered so far is degree X on the MSK scale in 1940, while the area that experienced the degree VI and VII (severe ground motion and building damage) includes Romania, the Republic of Moldova, a large part of Bulgaria and south-western Ukraine and east part of Serbia.

The strong intermediate-depth earthquakes1940, Mw=7.7; 1977, Mw=7.4; 1986, Mw=7.1; 1990, May 30, Mw=6.9; 1990, May 31, Mw=6.4; and 2004, Mw=6.0. are largely felt in Serbia and caused extensive damage in east parts of the country.

NATO SfP 984374 | Improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries

DATAThe data were obtained from the catalogue of macroseismic data. The

“Macro-catalogue of Serbia” for the period 306–2006 (6818 pages with 30,480 earthquakes) was compiled by different scientists in different time intervals; in 1940, the author was Jelenko Mihajlović.

As demonstrated by the analysis performed during the compilation of the Balkan catalogue (Shebalin et al., 1972), Mihajlović modified the used macroseismic scale over time, i.e., he inconsistently applied the Rossi–Forel and then the Mercalli scales.

Therefore damage field reports for Serbian territory given in the Macro catalogue until 1950, including the 1940 Vrancea event, have been reinterpreted using the MSK and European Macroseismic scales After 1964, the MSK scale is used in Serbia.

NATO SfP 984374 | Improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries

Sample page from the Macro-catalogue of Serbia for the

1940 Vrancea earthquake.

NATO SfP 984374 | Improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries

DATAEarthquake 1940, Mw=7.7

NATO SfP 984374 | Improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries

Local soil map based on EC-8

NATO SfP 984374 | Improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries

Hazard map TNRC=475y

Soil modification

NATO SfP 984374 | Improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries

1977th Vrancea eq- Nis time history of acceleration

NATO SfP 984374 | Improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries

Elastic response spectra horizontal components artificial acceleration from distant earthquake

soil type C vs=260m/sand

NIS acceleration damping 5%

020406080

100120140160180

0.00 1.00 2.00 3.00 4.00

T (sec)

Se (cm

/s2) .

Nis-X

Nis-Y

syn-Vrancea Nis-x

syn-Vrancea-Nis-y

Synthetic acceleration for 1940th Vrancea eq East Serbia

Elastic response spectra horizontal components artificial acceleration from distant earthquake

soil type C vs=260m/sand

NIS acceleration damping 5%

0

50

100

150

200

250

0.00 1.00 2.00 3.00 4.00T (sec)

Se

(cm

/s2)

.

Nis-X

Nis-Y

syn-Vrancea-ES-x

syn-Vrancea-ES-y

CONCLUSION

The effect of intermediate-depth Vrancea earthquakes on all buildings and structures, which have a long oscillation period and are located on soft and unconsolidated soil, is evident in the spatial distribution of the macroseismic effects of the 1940 Vrancea earthquake.

The question remains whether the probabilistic approach,which is to be adopted, is able to account for the significanteffect of distant earthquakes (such as the ones in Vrancea)

in the area of East and Central Serbia.

NATO SfP 984374 | Improvements in the Harmonized Seismic Hazard Maps for the Western Balkan Countries