1. 1 Seismogenic zones of NW Croatia Bruno TOMLJENOVIĆ 1, Davorka HERAK 2, Marijan HERAK 2 & Koraljka KRALJ 3 1 University of Zagreb, Faculty of Mining, Geology & Petroleum Engineering, Pierottijeva 6, Zagreb 2 University of Zagreb, Faculty of Sciences, Department of Geophysics, Horvatovac bb, Zagreb 3 INA Oil Company d.d. Zagreb, Exploration Department, Šubićeva 29

2. 2  Tectonic history & Pliocene-Quaternary faulting  Seismicity  Seismogenic zones: seismicity & tectonics STRUCTURE OF THIS LECTURE:

3. 3 ALPS CARPATHIANS DINARIDES PANNONIAN BASIN ADRIATIC BASIN Tectonic position: at the “triple junction” between the Alps, Dinarides & Pannonian basin

4. 4 Mesozoic - Paleogene tectonic history: a part of the suture between European and Adriatic plates after Schmid et al. (2008) Sharp deviation from overall NW-SE into NE-SW trend of Internal Dinarides is due to CCW-rotation and tectonic escape during the Oligocene- Earliest Miocene (Tomljenović et al., 2008)

5. 5  Neogene-recent tectonic history: a part of the Pannonian b. Syn-rift phase: extension by normal faulting (ca. 20 – 15 Ma) – opening of numerous sub-basins Post-rift phase: regional thermal subsidence (ca. 15 – 5 Ma) without significant faulting Local basin inversion: compression by folding & reverse faulting (ca. 5 Ma to Recent) after Tomljenović & Csontos (2001)

6. 6 Traces of Pliocene-Quaternary active faults

7. 7 after Herak et al. (subm.) Seismicity of NW Croatia

8. 8 after Herak et al. (subm.) Fault-plane solutions in NW Croatia

9. 9 Seismogenic zones of NW Croatia 51 2 3 4

10. 10 Seismogenic zone 1: Ivanščica-Kalnik

11. 11 Seismogenic zone 2: Bilogora-Drava

12. 12 Seismogenic zone 3: Medvednica - Zagreb area after Tomljenović (2002)

13. 13 North Medvednica Fault Kašina Fault Sava Fault Medvednica - Zagreb area: Base Pliocene structural map

14. 14 Seismogenic zone 3: Medvednica-Zagreb

15. 15 Seismogenic zone 3: Medvednica-Zagreb

16. 16 Seismogenic zone 4: Žumberak - Samoborsko gorje

17. 17 Seismogenic zone 5: Pokupje

18. 18 5 1 2 3 4  In general, there is a good correlation between a) location and kinematics of Pliocene-Quaternary active faults, b) concentration of earthquakes and c) calculated and available FPS-s; Conclusions:

19. 19 5 1 2 3 4  However, attribution of seismic events to particular faults is still highly tentative and asks for a more precise data base, both on faults and hypocentres; Conclusions:

20. 20  Zagreb area, which is considered as the most vulnerable part of NW Croatia, is located within a tectonic block bounded by the three Pliocene-Quaternary active faults; Conclusions: North Medvednica Fault Kašina Fault Sava Fault

21. 21  There is a positive correlation between earthquake focii, FPS data, location and kinematics of the North Medvednica, Kašina and Sava faults;  These faults are considered as the major seismogenic sources in Medvednica - Zagreb seismogenic zone, responsible for historic earthquakes and capable to generate future events with M = 6 !!! Conclusions: