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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

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Tectonic history & Pliocene-Quaternary faulting

Seismicity

Seismogenic zones: seismicity & tectonics

STRUCTURE OF THIS LECTURE:

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ALPS

CARPATHIANS

DINARIDES

PANNONIANBASIN

ADRIATIC BASIN

Tectonic position: at the “triple junction” between the Alps, Dinarides & Pannonian basin

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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)

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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)

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Traces of Pliocene-Quaternary active faults

7after Herak et al. (subm.)

Seismicity of NW Croatia

8after Herak et al. (subm.)

Fault-plane solutions in NW Croatia

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Seismogenic zones of NW Croatia

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Seismogenic zone 1: Ivanščica-Kalnik

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Seismogenic zone 2: Bilogora-Drava

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Seismogenic zone 3: Medvednica - Zagreb area

after Tomljenović (2002)

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NorthMedvednica

Fault KašinaFault

SavaFault

Medvednica - Zagreb area: Base Pliocene structural map

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Seismogenic zone 3: Medvednica-Zagreb

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Seismogenic zone 3: Medvednica-Zagreb

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Seismogenic zone 4: Žumberak - Samoborsko gorje

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Seismogenic zone 5: Pokupje

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In general, there is a good correlation betweena) location and kinematics of Pliocene-Quaternary active faults, b) concentration of earthquakes and c) calculated and available FPS-s;

Conclusions:

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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:

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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:

NorthMedvednica

Fault KašinaFault

SavaFault

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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: