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Improvement and Harmonization of Serbia BSHAP Earthquake Catalogue

WORKSHOP FOR THE NATO SCIENCE FOR PEACE PROJECT “ HARMONIZATION OF SEISMIC HAZARD MAPS FOR THE WESTERN BALKAN COUNTRIES ” Belgrade , Serbia April, 25 – 26 20 13. Improvement and Harmonization of Serbia BSHAP Earthquake Catalogue.

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Improvement and Harmonization of Serbia BSHAP Earthquake Catalogue

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  1. WORKSHOP FOR THE NATO SCIENCE FOR PEACE PROJECT “HARMONIZATION OF SEISMIC HAZARD MAPS FOR THE WESTERN BALKAN COUNTRIES” Belgrade, Serbia April, 25 – 26 2013 Improvement and Harmonization of Serbia BSHAP Earthquake Catalogue

  2. The first stage in the preparation of a new Seismic Hazard Map is preparation of the earthquake catalogue. • Since the publication of the Catalogue for Balkans in 1974 many earthquake catalogs have been published, but they are mainly compilations of primary sources, without verification of the main parameters. • Extensive investigations have been conducted in recent years to revise available catalogs using large number of internal catalogs which are combination of parametric catalogs and authentic data on earthquakes and their effects, as well as using bulletin data published by ISC, EMSC and seismic networks in region.

  3. The data for the earthquake catalog preparation can be classified into three time periods, which differ in accuracy and data sources: • I. Historical period (up to 1893); • II. Early instrumental period (1983-1970); • III. Instrumental period (1970-up to now). • The diversity of the data sources and techniques of earthquake location, evident in those three periods, had for its consequence differences in the level of accuracy of all main parameters. • We came to the conclusion that it is necessary to verify and re-interpret events in National catalog, especially strong earthquakes with intensities >= 6.

  4. I Historical period (before 1893) • The earliest information on earthquakes in Serbia are dating from 1456. Earthquakes in this period have unreliable geographic coordinates because of poor records based on which they were located. Their seismic intensity was defined mostly based on small number of poorly defined data, while the depth of their hypocenters remained unknown. • These earthquakes only represent evidence of the seismic activity in the area and a qualitative definition of energy levels. Locations of the epicenters are useful base for seismic zone delineation. • Since 1879 Golubac - Moldova Noua earthquake, the collection and systematization earthquake effects significantly increased. Those data were the basis for the assessment of earthquake intensities, macroseismic magnitudes and depths acording to intensity distribution.

  5. II Early instrumental period (1893-1970) • Macroseismic data base of strong earthquakes for this period together with instrumentally recorded data, offered a reliable basis for the assessment of eq parameters with sufficient accuracy. • Instrumentally recorded earthquakes from this period were relocated using seismic models calculated for the territory of Serbia, while their magnitudes were redefined using all available data. Hypocenter depths were calculated and verified comparing them with the distribution of macro seismic effects in relocation procedure. • For the strongest events which occurred on the territory of Serbia, in the procedure of earthquake intensity redefinition, all available newspaper and other reports and photos were used, including seismic ground deformations. European Macroseismic Scale criteria for intensity assessment were applied and vulnerability class of the buildings in the observed time periods was also taken into account.

  6. Preparation of the catalogue, 1893-1970 Available data sources • Macro seismic parametric catalogue: Catalogue of earthquakes, Part I, Part II, UNDP- UNESCO Survey of the Seismicity of the Balkan Region, 1974; • Earthquake Catalogue for Central and Southeastern Europe 342 BC - 1990 AD, 1998 (Shebalin, Leydecker, 1998) • Isoseismic maps • Macro seismic earthquake catalogue in Seismological Survey of Serbia and other studies of earthquakes • Primary historical sources (photographs, witness descriptions in magazines, other)

  7. The first catalog prepared for the Balkans was well known UNESCO/UNDP Project “Survey of the Seismicity of the Balkan Region”, edited in 1974. • In the catalogue, earthquake magnitudes were calculated from intensity distribution. • Estimation of intensities were based on values expressed in various macro seismic scales. Intensity scales were not adequately recalculated, so that intensities of all strong earthquakes were mostly overrated.

  8. For a historical and early instrumental period, Catalogue for Central and Southeastern Europe (1998) is relevant. Magnitudes in this catalog are Ms and mb, determined using macro seismic and other data, 308 of 321 events with M>=3 in Catalog are before 1990 Magnitudes: 130 events are MS, Macrosismique and mixed determinations (rough estimation of MS from observed I max and supposed depth included) with error code : • b = ± 0.3 • c = ± 0.5 • d = ± 0.7 • e = ± 1.0 • f = ± 1.5 • 129 events are MS, Direct measurements with error code : • k = ± 0.5 • l = ± 0.7 Coordinate determination: most events are macroseismic determinations Analysis catalog led to the conclusion that it should be revised

  9. Preparation of the cataloguehistorical and early instrumental period (1879-1970) • The assessment procedure of the parameters for strong historical earthquakes has been applied to earthquakes for the period 1879 - 1970. • Intensities were re-estimated using original description of the effects: 1.003 out of 5.188 events with Io>=5 from original macro seismic catalog recorded up to 1970 are checked and processed • Epicenters were relocated using local seismotectonic models • Based on area within isoseismic areas, earthquake parameters - magnitude and focal depth were assessed.

  10. VIII-IX 1893 Svilajnac earthquake is one of the best documented with data collected in the field and obtained from the local reports Old Isoseismal Map of the 1893 Svilajnac Earthquake

  11. Photos show the effects on buildings and in soil in 1893 Svilajnac earthquake In the Monograph “Earthquakes in Serbia in 1893” geologists Jovan Zujovic and Djordje Stanojevic described in detail efects obtained on the field immediately after the earthquake.

  12. Adobe brick-vulnerability class A “BONDRUK”-vulnerability class B Photos show typical buildings in Serbia in the end of 19. century. Vulnerability class of most buildings in epicentral area is A and B – fieldstone, earth brick, simple stone. Within the first isoseismal area, it was observed that many buildings class B had 3. degree damages and a few 4. degree. Many buildings class A had 4. degree damages and few 5. degree.

  13. Lokacija Lat N Lon E Ii Troponje 44.160 21.270 8 Subotica 44.150 21.340 8 Medvedja 44.166 21.350 8 Gladna 44.083 21.300 8 Vel. Popo 44.116 21.350 8 Svilajnac 44.233 21.200 8 Grabovac 44.180 21.210 8 Sedlari 44.183 21.290 8 Vlaska 44.000 21.350 7 Lapovo 44.166 21.100 7 Bobova 44.233 21.250 7 Savac 43.850 21.366 7 Orasje 44.366 21.083 7 Vel. Plana44.500 21.050 7 Djurinac 44.233 21.350 7 Zabari 44.366 21.166 7 Jagodina 44.000 21.233 7 Kupinovac44.200 21.316 7 Salakovac 44.566 21.283 7 M. Crnice 44.550 21.283 7 Dvoriste 44.100 21.533 7 Based on classification in EMS scale intensity 8-9 was assessed in epicentral area. Following the same procedure, intensities 7, 6, 5 were assigned. Magnitude assessment is based on: Checking M from available catalogs Considering liquefaction phenomena (5.7-5.9) Using Musson equation for I=3, I=4 area Checking our equation for I=5 area.

  14. Isoseismal Map of the 1893 Svilajnac Earthquake According to the area affected with particular intensity and using intensity attenuation relation, Ii=1.3786 M - 3.243 D + 3.4019 magnitude 5.8 and 8 km depth was estimated. Distribution of highest seismic intensity within first isoseismal is one of the most important information about seismotectonics in epicentral area and wider seismic zone which is important for seismic hazard calculation.

  15. III Instrumental period (1970-up to now) • As the number of seismological station increased and was accompanied by a constant improvement of the quality of recorded data • Large high-quality data base was accumulated and as a consequence made it possible to work on various seismological research, such as defining regional seismic and seismotectonic models. • Extensive studies have been conducted in recent years to revise earthquake catalog by making use of numerous internal catalogs (combination of parametric catalogs and authentic earthquake data and their effects), as well as the bulletin data published by ISC, EMSC and seismic networks in region. • 1970-1990: 457 events M>=3 checked and/or processed Number of eq`s increased ~50% comparing to Shebalins catalog.

  16. Preparation of the catalogueAll available data are processed in program “Potres” using most reliable data Local and regional velocity models are used and tested to fit the best solution and minimum correction.Example is numerical processing of 1927 Rudnik earthquake, M=5.9, Io=8 which is recorded at 63 stations all over the world.

  17. Earthquake Catalogue M>=3.5 ~ about 320 earthquakes Io>=6 with epicenters in the territory of Serbia are processed for BSHAP I

  18. Earthquake Catalogue M>=3.0 >880 earthquakes Io>=5 in macroseismic catalog are processed for BSHAP II, ~600 events in total are added to Catalog ~4.560 events with Io=3-4 in macroseismic catalog to be checked, many of them having usefull informations which enables assessment of magnitude and focal depth

  19. Unification of the magnitude scales • For a historical and early instrumental period magnitudes Ms and Mb are used • For strongest instrumentally recorded earthquakes, magnitude Mlh is often determined, which corresponds to Mw magnitude for magnitude range 5=<M=<8. • For the period between 1963 and 2005, the catalogue consists of the earthquakes re-assessed acording to ISC data in which Mb and Ms and Mlh for the strong earthquakes (from Wiechert and Mainka seismograms) are published. • Since 2005, magnitude ML have been determined for the earthquakes in Serbia. • Using 180 earthquakes with Ms/mb pairs in ISC Catalog, the relation for magnitude conversion is defined. • Ms=1.263(+/-0.054)mb-1.505(+/-0.244), for the magnitude range 3.5=<mb=<6.1. • Makroseismic magnitudes Mm ,M, Ms,up to 1970 are converted to unified Mw using the Scordilis relations, ~50% of those occurred before 1971, ~30% of all Mw unified are calculated based on Scordilis relations

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