Seismic hazard modeling for Bulgaria D. Solakov, S. Simeonova

Seismic hazard modeling for Bulgaria D. Solakov, S. Simeonova

Bulgarian seismic network and foreign stations used in epicenter location

Sismicity in Bulgaria and surroundings (M 4.)

Epicentral map for Bulgaria and surroundings (after 198, all recorded quakes)

SEISMIC ZONING MAP 1961-1964 First building code - 1957 SEISMIC ZONING MAP 1977

SEISMIC SOURCES SEISMIC ZONING MAP 1987, return period 1 years 7.6-8. 7.1-6.6-7. 6.1-5.6-6. 5.1-4.6-5. 4.1-4.1-4.6-5. 4.1-4.1-4.1-4.6-5. 4.6-5. 4.6-5. 4.1-4.1-4.6-5. 4.6-5.

PROBABILISTIC SEISMIC HZARD ASSESSMENT The probability that a ground motion parameter, Z, at a given site, will exceed a specified level, z, during a given time period, t, is given by the expression: P(Z z t)=1-e - (z)t (z)t where (z) is the average frequency during time period t at which the level of ground motion parameter Z exceeds z at the site, resulting from earthquakes in all sources in the region. The frequency of exceedance, (z) is calculated by: ( z) n n ( m ) u m m f ( m) f ( r m) P( Z z m, r) drdm n (m o ) is the frequency of earthquakes on source n above a m o (min. mag. of ing. Importance); f(m) is the PDF for events between m o and maximal event for the source m u ; f(r m) is the PDF for distance to the earthquake rupture; P(Z z m,r) is the probability that for a given magnitude m earthquake at a distance r from the site, the ground motion exceeds level z.

A seismic source model is developed for PSHA for the territory of Bulgaria. The model is based on complex geodetic, geological, geophysical and seismological data and is presented in Fig. For each source are defined the all parameters describing the seismicity in the source. Two cases are considered: 1.All sources are areal sources earthquakes are randomly distributed in the corresponding source 2.Smaller earthquakes are randomly distributed in the source while stronger earthquakes are happened only on the faults defined in the source. The final result is a mean of the two considered cases. The hazard was evaluated for a grid with cell size.5 x.5.

COMPLEX GEOLOGO-GEOPHYSICAL AND SEISMOLOGICAL MAP

Influence of intermediate Vrancea earthquakes

DEAGGREGATION OF THE 475 YEARS HAZARD Northern cities The city of Varna The city of Targovishte.14.25.12.1.8.6.4.2 5. 6. 7..2.15.1.5 5. 6. 7. 2 4 6 8 1 12 14 16 18 2 22 24 26 28 3 32 34 7. 6. 5. Normalized number of exceedance Distance (km) 2 4 6 8 1 12 14 16 18 2 22 24 26 28 3 7. 6. 5. M Normalized number of exceedances Distance (km) M The city of Dobrich The city of Shumen.25.3.2.15.1.5 5. 6. 7..25.2.15.1.5 5. 6. 7. 2 4 6 8 1 12 14 16 18 2 22 24 26 28 3 32 34 7. 6. 5. Normalized number of exceedance Distance (km) 2 4 6 8 1 12 14 16 18 2 22 24 26 7. 6. 5. Normalized number of exceedances Distance (km) M M

DEAGGREGATION OF THE 475 YEARS HAZARD Southern cities The city of Stara Zagora The city of Sliven.12.25.1.8.6.4.2 5. 6. 7..2.15.1.5 5. 6. 7. The city of Yambol The city of Burgas.25.25.2.15.1.5 5. 6. 7..2.15.1.5 5. 6. 7. 2 4 6 8 1 12 14 16 18 2 7. 6. 5. Normalized number of exceedances Distance (km) 7. 6. 5. M 2 4 6 8 1 12 14 16 18 2 22 24 26 28 3 32 34 36 38 4 Normalized number of exceedances 5. 6. 7. 2 4 6 8 1 12 14 16 18 2 22 24 26 28 3 32 34 36 Normalized number of exceedance Distance (km) 5. 6. 7. 2 4 6 8 1 12 14 16 18 2 22 24 26 28 3 32 34 36 Normalized number of exceedances Disrance (km) M M Distance (km) M

DEAGGREGATION OF THE 475 YEARS HAZARD South-Eastern part South-East 475 г..8.7.6.5.4.3.2.1 Normalized number of exceedances 5. 6. 7. 8. 8. 7. 6. 5. M 4 8 12 16 2 24 28 32 36 Distance (km) 4 44 48

DETERMINISTIC HAZARD ASSESSMENT Akkar and Bommer (29, rev:21) - Akkar S, Bommer JJ (21) Empirical Equations for the Prediction of PGA, PGV, and Spectral Accelerations in Europe, the Mediterranean Region, and the Middle East. Seismological Research Letters 81 (2): 195-26. Boore and Atkinson (28) - Boore, D.M. and Atkinson G. M. (28), Ground-Motion Prediction Equations for the Average Horizontal Component of PGA, PGV, and 5%-Damped PSA at Spectral Periods between.1 s and 1. s Earthquake Spectra, Vol. 24, No. 1, pp: 99 138 Chiou and Youngs (28) - Chiou, B.S:J. and R.R. Youngs (28) An NGA Model for the Average Horizontal Component of Peak Ground Motion and Response Spectra Earthquake Spectra, Vol. 24, No. 1, pp: 173 215 Campbell and Bozorgnia (28) - Campbell, K. W. and Y. Bozorgnia (28) NGA Ground Motion Model for the Geometric Mean Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response Spectra for Periods Ranging from.1 to 1 s Earthquake Spectra, Vol. 24, No. 1, pp: 139 171 Abrahamson and Silva (28) - Abrahamson, N. and W. Silva (28) Summary of the Abrahamson & Silva NGA Ground-Motion Relations Earthquake Spectra, Volume 24, No. 1, pp. 67 97

Active faults

5%-Damped Pseudo-Absolute Acceleration Response Spectrum 5%-Damped Pseudo-Absolute Acceleration Response Spectrum 1 1 1 1 Spectral Acceleration).1.1 Spectral Acceleration).1.1.1.1.1 Period (s) 1 1.1.1.1 Period (s) 1 1 Median Median + N.σ Median Median + N.σ Bourgas, Fault length=64 km, M=7.2, distance=31km Varna, M=8, distance=39km

National Institute of Geophysics, Geodesy and Geography