Crustal structure at the contact of the Dinarides and Pannonian basin based on 2-D seismic and gravity interpretation of the Alp07 profile in the ALP 2002 experiment

Abstract

S U M M A R YThe area of this study includes the contact between the Dinarides and the Pannonian basin, as a relation between the Adriatic microplate and Pannonian segment. Our analysis was carried out on profile Alp07, which is a part of the ALP 2002 experiment. ALP 2002 was large international seismic experiment that focused on the lithospheric structure of the Eastern Alps and surrounding areas. Profile Alp07 is one of several refraction and wide-angle reflection profiles located in the transition from the Adriatic microplate, through the Dinarides, and into the Pannonian basin. This 300-km-long profile extends from Istra, Croatia to the Drava River at Hungarian-Croatian border in a WSW-ENE direction. It is oriented approximately perpendicular to the Dinarides, the main faults in the Adriatic region, and the contact between the Dinarides and Pannonian basin. 2-D seismic modelling was done using tomographic inversion and ray tracing techniques. The Moho depth is the greatest in the area of the Dinarides, reaching about 40 km and is shallowest (30-20 km) in the Pannonian basin area. At the boundary between these provinces, the depth changes rather suddenly. In order to obtain additional constraints on the crustal structure, 2-D gravity modelling was also performed. The layer boundaries were retained from the seismic model as there was no need to change them during modelling, since varying densities in the model produced a good fit to the data. A geological model was constructed based on both geophysical models. Three types of the crust were found along profile: the Dinaridic and the Pannonian crusts that are separated by a relatively narrow transition zone. The Dinaridic upper crust is characterized by low seismic velocities and densities, but its lower crust has high velocities and densities. The Pannonian crust can be seen as unique layer characterized by both low seismic velocities and densities. Large lateral and vertical changes in densities and seismic velocities can be found in the transition zone. Troughs in the seismic model at the level of the Mohorovičić discontinuity are interpreted as major faults in the lithosphere. Three main lithospheric faults were identified: in northeastern part of the Dinarides under the Sava depression and under the Drava depression. The first one may be considered as a result of subduction of the Adriatic microplate under the Pannonian segment. Similar movements are also defined within the transition zone, where the Pannonian segment is gradually rising over on the Adriatic microplate.

Crustal structure of the Pannonian Basin: The AlCaPa and Tisza Terrains and the Mid-Hungarian Zone

“…More recently, the analysis of ambient seismic noise from a basin-wide array of broad-band seismic recorders has enabled the application of tomographic techniques to determine a new high-resolution crustal velocity model for the entire region(Ren et al, 2013). This model is in broad agreement with prior compilations of controlled source data(Grad et al, 2009;Tesauro et al, 2008) but important differences emerge in specific places that have not previously been traversed by reflection / refraction profiles. The density of surface wave paths that are used in the analysis ofRen et al (2013) implies that all parts of the model are subject to constraints on the velocity variation that are comparable in quality and objectivity, though horizontal resolution decreases with depth.…”

“…Also shown on Fig. 7 are the corresponding Moho depth profiles extracted from the regional compilations of Tesauro et al (2008) and Grad et al (2009). All four datasets generally agree on Moho depth across most of the basin, but the two compilations do not show the Moho deepening to the SE, as is evident in both RF Moho depths and the V S field from surface wave tomography.…”

“…Earlier seismic investigations of the Pannonian Basin crust have relied largely on controlled source experiments (as summarized by Tari et al, 1999 andGrad et al, 2009) and also suggest that reduced crustal thickness occurs in a diffuse band that crosses the basin beneath the MHZ.…”

Geophysical investigation of the crust of the Upper Adriatic and neighbouring chains

“…Interesting aspects of the upper and lower crust units are here related to the collision between EU and PA and to the subsequent extension of PA, The TRANSALP lateral extrusion model with the STR as a lithospheric decoupling separating the AD from EU, with EU underthrusting AD crust, was reinforced by ALP2002 WAR/R acquisitions (see the position map in Fig. 1 with thickened lines tracking the published profiles by Brückl et al (2007); Grad et al (2009);Š umanovac et al (2009) and the interpretative sections for ALP-02 and -01, based on velocities indications, in Figs. 9 and 10).…”

Hungarian national report on IASPEI 2007–2010

“…The Alp07 profile was investigated by both active and passive seismic experiments utilising analysis of receiver functions and integrating gravity analysis (Sumanovac et al 2009). The Alp07 sections stretches from Istria through the Dinarides to the Pannonian Basin in a WSW-ENE direction.…”