Crustal structure of the Carpathian–Pannonian region from ambient noise tomography

Abstract

We use ambient noise tomography to investigate the crust and uppermost mantle structure beneath the Carpathian-Pannonian region of Central Europe. Over 7500 Rayleigh wave empirical Green's functions are derived from interstation cross-correlations of vertical component ambient seismic noise recordings (2005-2011) using a temporary network of 54 stations deployed during the South Carpathian Project (2009-2011), 56 temporary stations deployed in the Carpathian Basins Project (2005)(2006)(2007) and 100 permanent and regional broad-band stations. Rayleigh wave group velocity dispersion curves (4-40 s) are determined using the multiple-filter analysis technique. Group velocity maps are computed on a grid of 0.2 • × 0.2 • from a non-linear 2-D tomographic inversion using the subspace method. We then inverted the group velocity maps for the 3-D shear wave velocity structure of the crust and uppermost mantle beneath the region. Our shear wave velocity model provides a uniquely complete and relatively high-resolution view of the crustal structure in the Carpathian-Pannonian region, which in general is validated by comparison with previous studies using other methods to probe the crustal structure. At shallow depths (<10 km) we find relatively high velocities below where basement is exposed (e.g. Bohemian Massif, Eastern Alps, most of Carpathians, Apuseni Mountains and Trans-Danubian Ranges) whereas sedimentary areas (e.g. Vienna, Pannonian, Transylvanian and Foçsani Basins) are associated with low velocities of well defined depth extent. The mid to lower crust (16-34 km) below the Mid-Hungarian Line is associated with a broad NE-SW trending relatively fast anomaly, flanked to the NW by an elongated low-velocity region beneath the Trans-Danubian Ranges. In the lowermost crust and uppermost mantle (between 30 and 40 km), relatively low velocities are observed beneath the Bohemian Massif and Eastern Alps but the most striking features are the broad low velocity regions beneath the Apuseni Mountains and most of the Carpathian chain, which likely is explained by relatively thick crust. Finally, most of the Pannonian and Vienna Basin regions at depths >30 km are relatively fast, presumably related to shallowing of the Moho consequent on the extensional history of the Pannonian region.

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.…”

“…1). Figure 6 shows the interpreted crustal structure and velocity section We also compare our RF Moho depth picks with shear-wave velocity sections taken from a recent tomographic inversion of crustal velocities determined from surface wave analysis (ambient noise correlation) by Ren et al (2013). On the CBP2x and CBP3x profiles, the RF Moho picks generally are within the range V S = 3.7-3.9 km/s (Fig.…”

“…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. Their images show clearly the areal extent of the region affected by the failed Tisza rift in the upper 5 to 10 km,…”

Ambient Seismic Noise Tomography of a Loess High Bank at Dunaszekcső (Hungary)

“…Sabra et al, 2005a;Shapiro et al, 2005;Yang et al, 2007;Cho et al, 2007;Bensen et al, 2009) and 2) time-frequency phase weighted stacking (tf-PWS) described by Schimmel and Gallart (2007), which has been applied in some recent ambient seismic noise tomography studies (e.g. Ren et al, 2013;Dias et al, 2015).…”

“…In addition, the measurement time depends on station distance, the shorter the distance, the lesser the time required (Sabra et al, 2005b;Gouedard et al, 2008). This method can be equally well used on continental (Yang et al, 2007;Bensen et al, 2009), regional (Szanyi et al, 2013;Ren et al, 2013;Dias et al, 2015), local (Renalier et al, 2010;Stankiewicz et al, 2012) and engineering-geotechnical scale (Picozzi et al, 2009;De Nisco and Nunziata, 2011;Pilz et al, 2012Pilz et al, , 2014.…”