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Composite Seismogenic Sources

General information
HRCS020
Eastern Adriatic offshore - Central
Kastelic V.(1), Tiberti M.M.(1), Basili R.(1)
Kastelic V.(1), Tiberti M.M.(1), Basili R.(1), Ridente D.(2)
1) Istituto Nazionale di Geofisica e Vulcanologia; Sismologia e Tettonofisica; Via di Vigna Murata, 605, 00143 Roma, Italy
2) CNR; Istituto di Geologia Ambientale e Geoingegneria; Roma, Italy
27-Mar-2009
17-Jan-2012
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Details
HRIS001
 
Parametric information
ParameterQualityEvidence
2.0 EJ Inferred from regional tectonic and geologic considerations.
12.0 EJ Inferred from regional tectonic and seismological considerations.
270…330 LD Based on map of active faults (Ivanic et al., 2006).
35…60 EJ Inferred from regional geologic considerations and focal mechanism data.
70…100 EJ Infered from structural and geodynamic considerations.
0.05…0.2 LD Based on results of geodynamic modelling (Kastelic and Carafa, 2012) and geologi
6.0 EJ Inferred from fault characteristics, earthquake data and regional geodynamics.
LD=Literature Data; OD=Original Data; ER=Empirical Relationship; AR=Analytical Relationship;EJ=Expert Judgement;
Active Faults
Active Folds
Commentary

 

 COMMENTS

The geological and structural conditions of the Central Adriatic is characterized by the presence of two thrust belts with opposite vergence – the Apennines to the west and the External Dinarides to the east. In the literature this area is often referred to as Mid Adriatic Ridge (e.g. Finetti, 1982; Scisciani and Calamita, 2009), Adriatic Ridge for its central-western part (e.g. Scrocca, 2006), Central Adriatic Deformation Belt (e.g. Argnani and Gamberi, 1995) or Mid Adriatic Basin (e.g. Fantoni and Franciosi, 2010). It is characterized by NW-SE structural highs (Grandic and Markulin, 2000; Scrocca et al., 2007) related to thrust-related folding (Argnani and Frugoni, 1997), active diapirism (Geletti et al., 2008; Del Ben et al., 2010) or to a combination of both processes (Bally et al., 1986). The Cenozoic compressional tectonic setting in this area was preceded by the Mesozoic extension and its horst-graben structural setting. Seismic and borehole data show that the early stages of compression caused the inversion of older normal faults (Scrocca et al., 2007; Scisciani and Calamita, 2009), while in the Plio-Quaternary the active thrusting was superimposed on the basement-involving normal faults (Scrocca et al., 2007) and shows lower dip angles with respect to older normal faults (Scrocca et al., 2007; Fantoni and Franciosi, 2010). Earthquake activity confirms that active compression is accommodated by thrust planes (Herak et al., 2005) showing gentler dips with respect to the normal faults.

This Source is located in the central part of the Central Adriatic. The sea-bottom of the area is covered by a layer of Quaternary and Pleistocene fluvial deposits underlain by Neogene (predominantly Pliocene) foredeep sedimentary clastics that overlie the earlier stage Eocene to Miocene foredeep flysch deposits (Fantoni and Franciosi, 2010). Deeper stratigraphic units consist of Mesozoic platform carbonates, Permian and Triassic clastic rocks with evaporite layers and Variscan basement units (Grandic and Markulin, 2000; Fantoni and Franciosi, 2010). An evaporite diapir rising from the Permian and Triassic host rocks towards the surface and protruding all the way to the sea-bottom is known to occur in this area (Grandic and Markulin, 2000; Geletti et al., 2008). The Jabuka shoal is formed by Triassic-Jurassic gabbro that appears to belong to the core of a small magmatic body (Juracic et al., 2004). The presence of magmatic rocks on the sea floor aligned in a narrow patch of NW-SE to WNW-ESE direction is attributed to thrust activity (Juracic et al., 2004; Herak et al., 2005), or to uplift processes connected to diapirism uprise (Grandic et al., 1999). The latter option is supported by the presence of both magmatic rocks and evaporites on the Jabuka island (Geletti et al., 2008).

This Source represents an active thrust fault uplifting the gabbro body in its hanging-wall across the evaporites lying in the footwall of the fault (Herak et al., 2005). To establish its location and parameters, we relied on seismic profiles (Grandic and Markulin, 2000; Grandic et al., 2002; Fantoni and Franciosi, 2010), gravity (Grandic et al., 2002), borehole (Grandic et al., 2002) and earthquake data (Herak et al., 2005). This Source originates in the Variscan basin and cuts through the Permian and Triassic clastic rocks, Mezosoic carbonates and Paleogene and Neogene foredeep rocks.

The depth of the upper edge of the source is based on the local geological characteristics of the fault area. The maximum source depth is based on seismic profiles (e.g. Fantoni and Franciosi, 2010) and earthquake data (Herak et al., 2005). The strike of the fault was determined based on the map of active faults of the area (Ivancic et al., 2006) and on the focal mechanisms of the 29 March 2003, Mw 5.5 Jabuka earthquake (Herak et al., 2005; Global CMT Catalog, available at http://www.globalcmt.org/) that occured on a segment of this Source. The dip was inferred from seismic profiles (e.g. Fantoni and Franciosi, 2010) and focal mechanism data (Herak et al., 2005), while the rake was mainly inferred from earthquake and regional geological data. We set the slip rate for this source based upon the results of geodynamic numerical modelling (Kastelic and Carafa, 2012) compared with geologically estimated values. We estimate a Mmax based upon the geometrical characteristics of the fault and the available data on neighbouring faults and regional data.

The geometry of this Source was modified with respect to the previous versions of DISS, where it was part of a longer that encompassed what currently are three separate Sources. During the revision process based on new available geological and geophysical information, we divided the longer source to better capture the geometrical characteristics of different segments of the fault system. The solution presented here and adopted by the DISS v. 3.2.0 and SHARE databases better describes the along-strike geometric (i.e. strike and dip) and activity (i.e. slip rate, as supplied by Kastelic and Carafa, 2012) characteristics. By presenting three seismogenic sources instead of a longer one, we do not imply any change in the seismogenic potential of this part of our model. Nevertheless, capturing the complexity of the sources in greater detail may return more accurate estimates of the expected ground shaking and tsunami potential to be used in Seismic Hazard Assessments (SHA).

 
Pictures

 

Map of Active faults in Croatia Details
Geological cross-section of the northern Dalmatian part of the Dinarides and off-shore Details
Seismotectonic profile through the area of Jabuka seismic sequence Details
Regional cross-sections Details
Long-term fault slip rates for the External Dinarides Details
References

 

Carafa, M. M. C., and V. Kastelic 2014 Earthquake rates inferred from active faults and geodynamics: the case of the External Dinarides. Boll. Geof. Teor. Appl., 55, 69-83.
Fantoni, R., and R. Franciosi 2010 Tectono-sedimentary setting of the Po Plain and Adriatic foreland. Rendiconti Lincei, 21, 0, 197-209, 10.1007/s12210-010-0102-4.
Kastelic, V. and M.M.C. Carafa 2012 Fault slip rates for the active External Dinarides thrust-and-fold belt. Tectonics, 31 (2012), p. TC3019 http://dx.doi.org/10.1029/2011TC003022.
Kastelic, V., P. Vannoli, P. Burrato, U. Fracassi, M. M. Tiberti and G. Valensise 2012 Seismogenic Sources In the Adriatic Domain. Marine and Petroleum Geology, http://dx.doi.org/10.1016/j.marpetgeo.2012.08.002.
Markušic, S. 2008 Seismicity of Croatia. in: E. S. Husebye (ed.), Earthquake Monitoring and Seismic Hazard Mitigation in Balkan coutries, NATO Science Series, Series IV: Earth and Environmental/Sciences, 79, 81-98.
Markusic, S., and M. Herak 1999 Seismic zoning of Croatia. Nat. Hazards, 18, 269-285.
Pondrelli, S., A. Morelli and G. Ekström 2004 European-Mediterranean regional centroid-moment tensor catalog: solutions for years 2001 and 2002. Phys. Earth Planet. In., 145, 127-147.
Pondrelli, S., A. Morelli, G., Ekström, S., Mazza, E., Boschi, and A. M. Dziewonski 2002 European-Mediterranean regional centroid-moment tensors: 1997-2000. Phys. Earth Planet. In., 130, 71-101.
Pondrelli, S., S. Salimbeni, G. Ekström, A. Morelli, P. Gasperini and G. Vannucci 2006 The Italian CMT dataset from 1977 to the present. Phys. Earth Planet. In., 159, 286-303.
Ustaszewski, K., M. Herak, B. Tomljenovic, D. Herak, and S. Matej 2014 Neotectonics of the Dinarides–Pannonian Basin transition and possible earthquake sources in the Banja Luka epicentral area. J. Geodyn., 82, 0, 52-68, 10.1016/j.jog.2014.04.006.
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