POMACI STRUKTURA I SEIZMOTEKTONSKA AKTIVNOST ZAPADNOG VELEBITA: NEKA NOVA OPAŽANJA

A permanent seismotectonic activity is present in the region of northern Velebit. Through history a number of earthquakes magnitudes of VIII° and IX° MCS are reported. In this century the most powerful earthquake of a magnitude of 5.8 occurred in 1916. The key tectonic movements that cause these earthquakes are dislocations of the Adriatic platform towards the north and the resistance of the Dinarides towards these movements. The tectonic dynamics of a structural arrangement depend on the relationship between stress and the deformation of structural units. According to the tectonic measurements performed on outcrops of major faults the following orientation of stress was obtained: from 20/25° to 200/205° in the northern Velebit region and 340 to 160° in the hinterland. Within the structural arrangement compression of space occurs which is well pronounced in the Novi Vinodolski area. Possible deformation of structures is manifested spatial diagonal reverse displacements accompanied by rotation of the structure. In the Velebit hinterland right horizontal tectonic transport was determined. In the zone of the transcurrent faull Žuta Lokva-Otočac-Bunić the spatial opening leads to the formation of pull-apart structures. Seismotectonically active zones occur in the contact region between the Adriatic platform and the Dinaridcs. Spatially its position is inclined and bent.U području sjevernog Velebita stalno je prisutna seizmotektonska aktivnost. U povijesti se više puta spominju potresi intenziteta VII° i IX° MCS. U ovom stoljeću najjači potres dogodio se 1916. godine magnitude 5,8. Ključni tektonski pokreti koji uzrokuju pojavljivanje potresa jesu pomaci Jadranske platforme prema sjeveru i odupiranje Dinarida tim pomacima. Tektonska dinamika strukturnog sklopa ovisi o odnosu stresa i deformacija strukturnih jedinica. Prema podacima terenskog mjerenja u izdancima najvažnijih rasjeda dobivena je orijen¬tacija stresa: u sjevernom Velebitu 20/25°-200/205° i u zaleđu 340-160°. U strukturnom sklopu nastaje kompresija prostora osobito izražena oko Novog Vinodolskog. Moguće deformacije struktura jesu dijagonalni reversni pomaci u prostoru uz rotaciju struktura. U zaleđu sjevernog Velebita utvrđen je desni horizontalni tektonski transport. U zoni transkurentnog rasjeda Žuta Lokva-Otočac-Bunić otvaranjem prostora oblikuju se strukture tipa pull-apart. Seizmotektonski aktivna zona pojavljuje se u prostoru dodira Jadranske platforme i Dinarida. Značajan je njezin kosi položaj u prostoru uz koncentraciju žarišta resa na dubinama do 34 km

Seismological and seismo-tectonical properties of the wider Zagreb area

Prikazani su učestalost i prostorna distribucija pojavljivanja potresa na širem zagrebačkom području. Uzimajući u obzir kompresiju u zoni Žumberačko-medvedničkog rasjeda, tektonske pomake dijelova Medvednice, amplitude pokreta i potrese koji su se dogodili, izdvojen je seizmotektonski najaktivniji prostor. Provedena analiza prostorne distribucije reziduala teorijski dobivenih i empirijskih intenziteta Zagrebačkog potresa iz 1880. potvrđuje veliki utjecaj lokalnih uvjeta tla.The frequency and territorial distribution of seismic activities in a wider Zagreb area are presented. The area most active from the seismo-tectonic standpoint was selected by taking into account compression in the Žumberak - Medvednica fault zone, tectonic movements in some parts of Medvednica, displacement amplitudes and past earthquakes. The analysis of territorial distribution of theoretical and empirical intensity residuals, the latter based on the earthquake that struck Zagreb in 1880, confirms that the influence of local soil conditions has been significant

THE STRUCTURAL FABRIC AND SEISMOTECTONIC ACTIVITY OF NORTHERN VELEBIT: SOME NEW OBSERVATIONS

A permanent seismotectonic activity is present in the region of northern Velebit. Through history a number of earthquakes magnitudes of VIII° and IX° MCS are reported. In this century the most powerful earthquake of a magnitude of 5.8 occurred in 1916. The key tectonic movements that cause these earthquakes are dislocations of the Adriatic platform towards the north and the resistance of the Dinarides towards these movements. The tectonic dynamics of a structural arrangement depend on the relationship between stress and the deformation of structural units. According to the tectonic measurements performed on outcrops of major faults the following orientation of stress was obtained: from 20/25° to 200/205° in the northern Velebit region and 340 to 160° in the hinterland. Within the structural arrangement compression of space occurs which is well pronounced in the Novi Vinodolski area. Possible deformation of structures is manifested spatial diagonal reverse displacements accompanied by rotation of the structure. In the Velebit hinterland right horizontal tectonic transport was determined. In the zone of the transcurrent faull Žuta Lokva-Otočac-Bunić the spatial opening leads to the formation of pull-apart structures. Seismotectonically active zones occur in the contact region between the Adriatic platform and the Dinaridcs. Spatially its position is inclined and bent