Seismotectonically Active Zones in the Dinarides

Seismotectonically active zones are formed due to displacements of segments of the Adriatic micro-plate that differ in size and in their rate of movement, and by the resistance of the rock masses of the Dinarides. The spatial position of these zones can be determined through the locations of earthquake foci. The zones of seismotectonic activity are then correlated with the most important faults on the surface. The seismotectonically active zones are relatively steeply inclined in the shallowest 10-20 km, which is caused by the oblique contacts between the Adriatic micro-plate and the Dinarides. The zones are curved at depth in many cases, which reflects the compression of the area. Curved parts of the zones are characterised by the greatest pressures and also by the most frequent earthquakes. Mildly inclined zones reflect the reverse displacements in the area, also probably the activity on contacts between rock masses of different density, or the extension of the Adriatic micro-plate subduction. The southern part of the plate is the most active. The greatest pressures caused by these movements occur in the area between Mljet island and Dubrovnik. Therefore the majority of earthquakes, and notably the strongest ones, occur in the area between Split, Imotski, Hvar island and Dubrovnik, as well as along the Montenegro coast in a SE direction

New data on Structural Relationships in the North Dalmatian Dinaride Area

Subsurface structural relationships are presented based on gravity data and seismic reflection profiles. Reflection marker horizons and the relative positions of different rock masses and structural units have been established, and are compared with surface observations. Active zones, marked by pronounced reflection boundaries in seismic profiles, have been established, the deepest of which are connected with the Dugi Otok fault zone. Below this interface, rock masses of the Adriatic platform underthrust the Dinarides. The active underthrusting plane reaches a depth of about 17 km. In the northern part of the area under consideration, contours of upthrown rock masses at depths of 5 to 11 km have been established. The area of numerous reverse faults is particularly active, and is defined on the surface by the Obrovac-Drnis-Klis fault. Reconstruction of tectonic movements indicates that rotation of structures and dextral strike slips have occurred, particularly along this fault zone

Recent Tectonic Activity in the Imotsko Polje Area

Displacements of the Adriatic microplate, particularly of its southern part, are of crucial importance for the understanding of recent tectonic movements. Deformations of the structural fabric and the resulting tectonic activity also encompass the studied area. There are four most active fault zones - Mosor-Biokovo, Zagvozd-Vrgorac-Metkovic, Trilj-Tihaljina-Capljina and Imotski-Medjugorje-Popovo polje. In the explored area, these zones delimit the Imotsko polje. The calculated regional stress is oriented in the range between 10-190° and 350-170°. The relationship between the orientation of structural units and stress enables reverse displacements, most frequently in the direction of the south and south-east. The change in stress orientation in the Mt. Biokovo hinterland makes the aforementioned fault zones surrounding the Imotsko polje favourably oriented in respect to the stress, thus enabling dextral horizontal tectonic transport of the structures in different fault blocks. In the two fault zones - Trilj-Tihaljina-Capljina and Imotski-Medjugorje-Popovo polje, there are 98 outcrops suitable for the structural geology measurements. The obtained data on the local stress orientation and spatial displacement of structures are the most important. The character of faults and the most active fault sections are marked, as well as the local structures that are formed due to strong horizontal component of structural displacement in the studied fault zones. Recent tectonic activity is confirmed by the occurrence of earthquakes. Spatial distribution of the earthquake epicentres depicts zones of seismotectonic activity that are related to the aforementioned most important fault zones. Two of the fault zones - Trilj-Tihaljina-Capljina and Imotski-Medjugorje-Popovo polje are especially well marked by earthquakes occurring at depths of between 3 and 15 km

Regional spreading of paleo-gravel formations in north-western Croatia and their geomorphological importance for explantion of morphogenesis and neotectonical movements

U ovom se članku obrađuje regionalna distribucija kvartarnih šljunčanih naslaga u dijelu sjeverozapadne Hrvatske, kao i njihovovo geomorfološko značenje u tumačenju morfogeneze reljefa i kvartarnih neotektonskih pokreta.Regionally distributed Quaternary fluvial gravel layers in North-western Croatia, which were by neotectonic movements subsequently removed at different hypsometrical levels, are discussed in the paper

Paleogeographic evolution of the Southern Pannonian Basin: 40Ar/39Ar age constraints on the Miocene continental series of notthern Croatia

The Pannonian Basin, originating during the Early Miocene, is a large extensional basin incorporated between Alpine, Carpathian and Dinaride fold-thrust belts. Back-arc extensional tectonics triggered deposition of up to 500-m-thick continental fluvio-lacustrine deposits distributed in numerous sub-basins of the Southern Pannonian Basin. Extensive andesitic and dacitic volcanism accompanied the syn-rift deposition and caused a number of pyroclastic intercalations. Here, we analyze two volcanic ash layers located at the base and top of the continental series. The lowermost ash from Mt. Kalnik yielded an 40Ar/39Ar age of 18.07 ± 0.07 Ma. This indicates that the marine-continental transition in the Slovenia-Zagorje Basin, coinciding with the onset of rifting tectonics in the Southern Pannonian Basin, occurs roughly at the Eggenburgian/ Ottnangian boundary of the regional Paratethys time scale. This age proves the synchronicity of initial rifting in the Southern Pannonian Basin with the beginning of sedimentation in the Dinaride Lake System. Beside geodynamic evolution, the two regions also share a biotic evolutionary history: both belong to the same ecoregion, which we designate here as the Illyrian Bioprovince. The youngest volcanic ash level is sampled at the Glina and Karlovac sub-depressions, and both sites yield the same 40Ar/39Ar age of 15.91 ± 0.06 and 16.03 ± 0.06 Ma, respectively. This indicates that lacustrine sedimentation in the Southern Pannonian Basin continued at least until the earliest Badenian. The present results provide not only important bench marks on duration of initial synrift in the Pannonian Basin System, but also deliver substantial backbone data for paleogeographic reconstructions in Central and Southeastern Europe around the Early–Middle Miocene transition

Geology, tectonics, geodesy and geodynamics of Croatia

This paper summarizes recent research activities on merging the geodetic, geologic and neotectonic evidence of geodynamics in Croatia. The area of the City of Zagreb, which is the boundary zone of Eastern Alps, Dinnarides and Pannonian Basin is included as well. It is shown here that the evidence for fractures of Eastern Adriatic differs from the previous hypotheses. This conclusion is derived from the results of various geodetic measurements: satellite positioning (GPS), astro-geodetic measurements of deflections of the vertical. These results are combined with geologic measurements and results of seismic activity studies in order to give more detailed and more accurate picture of the current situation in the tectonically very active region of Dinnarides. Several GPS-campaigns performed in the City of Zagreb area are examined as well. Due to the proximity of Croatian capitol, special attention has been paid to the effects of possible hazard on construction code

Correlation between geodetic and geological models in the geodynamic network of the city of Zagreb

Since 1997 till 2008, several series of precise GPS measurements have been conducted on specially stabilized points of Geodynamical Network of City of Zagreb with purpose of investigation of tectonic movements and related seismic activity of the wider area of the City of Zagreb. From this series of GPS measurements geodetic model of tectonic movements has been created. In the area of interest, independent geological investigations have been conducted through even longer period of time which resulted in geological model of tectonic movements. Comparison and correlation of these two independent models will be presented in this paper