scholarly journals Upper mantle deformation signatures of craton–orogen interaction in the Carpathian–Pannonian region from SKS anisotropy analysis

2020 ◽  
Vol 220 (3) ◽  
pp. 2105-2118 ◽  
Author(s):  
Laura Petrescu ◽  
Graham Stuart ◽  
Gregory Houseman ◽  
Ian Bastow
Keyword(s):  
Upper Mantle ◽  
Pannonian Basin ◽  
East European Craton ◽  
Tectonic Deformation ◽  
Seismic Zone ◽  
East European ◽  
Lithospheric Thickness ◽  
Delay Times ◽  
Moesian Platform ◽  
Fast Polarization

SUMMARY Since the Mesozoic, central and eastern European tectonics have been dominated by the closure of the Tethyan Ocean as the African and European plates collided. In the Miocene, the edge of the East European Craton and Moesian Platform were reworked in collision during the Carpathian orogeny and lithospheric extension formed the Pannonian Basin. To investigate the mantle deformation signatures associated with this complex collisional-extensional system, we carry out SKS splitting analysis at 123 broad-band seismic stations in the region. We compare our measurements with estimates of lithospheric thickness and recent seismic tomography models to test for correlation with mantle heterogeneities. Reviewing splitting delay times in light of xenolith measurements of anisotropy yields estimates of anisotropic layer thickness. Fast polarization directions are mostly NW–SE oriented across the seismically slow West Carpathians and Pannonian Basin and are independent of geological boundaries, absolute plate motion direction or an expected palaeo-slab roll-back path. Instead, they are systematically orthogonal to maximum stress directions, implying that the indenting Adria Plate, the leading deformational force in Central Europe, reset the upper-mantle mineral fabric in the past 5 Ma beneath the Pannonian Basin, overprinting the anisotropic signature of earlier tectonic events. Towards the east, fast polarization directions are perpendicular to steep gradients of lithospheric thickness and align along the edges of fast seismic anomalies beneath the Precambrian-aged Moesian Platform in the South Carpathians and the East European Craton, supporting the idea that craton roots exert a strong influence on the surrounding mantle flow. Within the Moesian Platform, SKS measurements become more variable with Fresnel zone arguments indicating a shallow fossil lithospheric source of anisotropy likely caused by older tectonic deformation frozen in the Precambrian. In the Southeast Carpathian corner, in the Vrancea Seismic Zone, a lithospheric fragment that sinks into the mantle is sandwiched between two slow anomalies, but smaller SKS delay times reveal weaker anisotropy occurs mainly to the NW side, consistent with asymmetric upwelling adjacent to a slab, slower mantle velocities and recent volcanism.

scholarly journals Automatic 1D integrated geophysical modelling of lithospheric discontinuities: a case study from Carpathian-Pannonian Basin region

2014 ◽  
Vol 44 (2) ◽  
pp. 115-131 ◽  
Author(s):  
Michal Grinč ◽  
Hermann Zeyen ◽  
Miroslav Bielik
Keyword(s):  
East European Platform ◽  
Pannonian Basin ◽  
Moho Depth ◽  
East European ◽  
Lithospheric Thickness ◽  
Eastern Carpathians ◽  
Moesian Platform ◽  
Lithosphere Thickness ◽  
Basin Region ◽  
Southern Carpathians

Abstract Using a very fast 1D method of integrated geophysical modelling, we calculated models of the Moho discontinuity and the lithosphere-asthenosphere boundary in the Carpathian-Pannonian Basin region and its surrounding tectonic units. This method is capable to constrain complicated lithospheric structures by using joint interpretation of different geophysical data sets (geoid and topography) at the same time. The Moho depth map shows significant crustal thickness variations. The thickest crust is found underneath the Carpathian arc and its immediate Foredeep. High values are found in the Eastern Carpathians and Vrancea area (44 km). The thickest crust modelled in the Southern Carpathians is 42 km. The Dinarides crust is characterized by thicknesses more than 40 km. In the East European Platform, crust has a thickness of about 34 km. In the Apuseni Mountains, the depth of the Moho is about 36 km. The Pannonian Basin and the Moesian Platform have thinner crust than the surrounding areas. Here the crustal thicknesses are less than 30 km on average. The thinnest crust can be found in the SE part of the Pannonian Basin near the contact with the Southern Carpathians where it is only 26 km. The thickest lithosphere is placed in the East European Platform, Eastern Carpathians and Southern Carpathians. The East European Platform lithosphere thickness is on average more than 120 km. A strip of thicker lithosphere follows the Eastern Carpathians and its Foredeep, where the values reach in average 160 km. A lithosphere thickness minimum can be observed at the southern border of the Southern Carpathians and in the SE part of the Pannonian Basin. Here, it is only 60 km. The extremely low values of lithospheric thickness in this area were not shown before. The Moesian Platform is characterized by an E-W trend of lithospheric thickness decrease. In the East, the thickness is about 110 km and in the west it is only 80 km. The Pannonian Basin lithospheric thickness ranges from 80 to 100 km.

scholarly journals Determination of rock densities in the Carpathian-Pannonian Basin lithosphere: based on the CELEBRATION 2000 experiment

2016 ◽  
Vol 46 (4) ◽  
pp. 269-287 ◽  
Author(s):  
Barbora Šimonová ◽  
Miroslav Bielik
Keyword(s):  
Lower Crust ◽  
Pannonian Basin ◽  
Average Density ◽  
East European Craton ◽  
P Wave ◽  
Seismic Velocities ◽  
Upper Crust ◽  
East European ◽  
P Wave Velocity

Abstract The international seismic project CELEBRATION 2000 brought very good information about the P-wave velocity distribution in the Carpathian-Pannonian Basin litosphere. In this paper seismic data were used for transformations of in situ P-wave velocities to in situ densities along all profiles running across the Western Carpathians and the Pannonian Basin: CEL01, CEL04, CEL05, CEL06, CEL09, CEL11 and CEL12. The calculation of rock densities in the crust and lower lithosphere was done by the transformation of seismic velocities to densities using the formulae of Sobolev-Babeyko, Christensen-Mooney and in the lower lithosphere also by Lachenbruch-Morgan’s formula. The density of the upper crust changes significantly in the vertical and horizontal directions, while the interval ranges of the calculated lower crust densities narrow down prominently. The lower lithosphere is the most homogeneous - the intervals of the calculated densities for this layer are already very narrow. The average density of the upper crust (ρ̅ = 2.60 g · cm−3) is the lowest in the Carpathian Foredeep region. On the contrary, the highest density of this layer (ρ̅ = 2.77 g · cm−3) is located in the Bohemian Massif. The average densities ρ̅ of the lower crust vary between 2.90 and 2.98 g · cm−3. The Palaeozoic Platform and the East European Craton have the highest density (ρ̅ = 2.98 g · cm−3 and ρ̅ = 2.97 g · cm−3, respectively). The lower crust density is the lowest (ρ̅ = 2.90 g · cm−3) in the Pannonian Basin. The range of calculated average densities ρ̅ for the lower lithosphere is changed in the interval from 3.35 to 3.40 g · cm−3. The heaviest lower lithosphere can be observed in the East European Craton (ρ̅ = 3.40 g · cm−3). The lower lithosphere of the Transdanubian Range and the Palaeozoic Platform is characterized by the lowest density ρ̅ = 3.35 g · cm−3.

scholarly journals A new model of the upper mantle structure beneath the western rim of the East European Craton

2014 ◽  
Vol 6 (1) ◽  
pp. 559-598
Author(s):  
M. Dec ◽  
M. Malinowski ◽  
E. Perchuc
Keyword(s):  
Upper Mantle ◽  
Seismic Velocity ◽  
Seismic Station ◽  
Structural Features ◽  
East European Craton ◽  
P Wave ◽  
Mantle Structure ◽  
Reflected Waves ◽  
East European ◽  
Upper Mantle Structure

Abstract. In this article we present a new 1-D P wave seismic velocity model (called MP1-SUW) of the upper mantle structure beneath the western rim of the East European Craton (EEC) based on the analysis of the earthquakes recorded at the Suwałki (SUW) seismic station located in NE Poland which belongs to the Polish Seismological Network (PLSN). This analysis was carried out due to the fact that in the wavefield recorded at this station we observed a group of reflected waves after expected P410P at epicentral distances 2300–2800 km from SUW station. Although the existing global models represent the first arrivals, they do not represent the full wavefield with all reflected waves because they do not take into account the structural features occurring regionally such as 300 km discontinuity. We perform P wave traveltime analysis using 1-D forward ray-tracing modelling for the distances up to 3000 km. We analysed 249 natural seismic events that were divided into four azimuthal spans with epicentres in the western Mediterranean Sea region (WMSR), the Greece and Turkey region (GTR), the Caucasus region (CR) and the part of the North Atlantic Ridge near the January Mayen Island (JMR). Events from each group were sorted into four seismic sections respectively. The MP1-SUW model documents bottom of the asthenospheric low velocity zone (LVZ) at the depth of 220 km, 335 km discontinuity and the zone with the reduction of P wave velocity atop 410 km discontinuity which is depressed to 440 km depth. The nature of a regionally occurring 300 km boundary here we explained by tracing the ancient subduction regime related to the closure of the Iapetus Ocean, the Rheic Ocean and the Tornquist Sea.

scholarly journals A new model of the upper mantle structure beneath the western rim of the East European Craton

Solid Earth ◽  
2014 ◽  
Vol 5 (1) ◽  
pp. 523-535
Author(s):  
M. Dec ◽  
M. Malinowski ◽  
E. Perchuc
Keyword(s):  
Upper Mantle ◽  
Seismic Velocity ◽  
Seismic Station ◽  
Velocity Model ◽  
East European Craton ◽  
P Wave ◽  
Mantle Structure ◽  
Reflected Waves ◽  
East European ◽  
Upper Mantle Structure

Abstract. We present a new 1-D P wave seismic velocity model (called MP1-SUW) of the upper mantle structure beneath the western rim of the East European Craton (EEC) based on the analysis of the earthquakes recorded at the Suwałki (SUW) seismic station located in NE Poland which belongs to the Polish Seismological Network (PLSN). Motivation for this study arises from the observation of a group of reflected waves after expected P410P at epicentral distances 2300–2800 km from the SUW station. Although the existing global models represent the first-arrival traveltimes, they do not represent the full wavefield with all reflected waves because they do not take into account the structural features occurring regionally such as 300 km discontinuity. We perform P wave traveltime analysis using 1-D and 2-D forward ray-tracing modelling for the distances of up to 3000 km. We analysed 249 natural seismic events from four azimuthal spans with epicentres in the western Mediterranean Sea region (WMSR), the Greece and Turkey region (GTR), the Caucasus region (CR) and the part of the northern Mid-Atlantic Ridge near the Jan Mayen Island (JMR). For all chosen regions, except the JMR group for which 2-D modelling was performed, we estimate a 1-D average velocity model which will characterize the main seismic discontinuities. It appears that a single 1-D model (MP1-SUW model) explains well the observed traveltimes for the analysed groups of events. Differences resulting from the different azimuth range of earthquakes are close to the assumed picking uncertainty. The MP1-SUW model documents the bottom of the asthenospheric low-velocity zone (LVZ) at the depth of 220 km, 335 km discontinuity and the zone with the reduction of P wave velocity atop 410 km discontinuity which is depressed to 440 km depth. The nature of the regionally occurring 300 km boundary is explained here by tracing the ancient subduction regime related to the closure of the Iapetus Ocean, the Rheic Ocean and the Tornquist Sea.

Spatiotemporal Variation of Crustal Anisotropy in the Source Area of the 2004 Niigata, Japan Earthquake

2019 ◽  
Vol 109 (4) ◽  
pp. 1331-1342
Author(s):  
Lingmin Cao ◽  
Honn Kao ◽  
Kelin Wang ◽  
Chuanxu Chen ◽  
Jim Mori ◽  
...  
Keyword(s):  
Stress Field ◽  
Source Area ◽  
Source Zone ◽  
Spatiotemporal Pattern ◽  
Tectonic Deformation ◽  
Tectonic Zone ◽  
Crustal Anisotropy ◽  
Stress Changes ◽  
Delay Times ◽  
Fast Polarization

Abstract We investigate the spatiotemporal pattern of crustal anisotropy in the source area of the 2004 Niigata earthquake (M 6.8) that occurred in the northern segment of the Niigata–Kobe tectonic zone, central Japan, by measuring shear‐wave splitting parameters from waveform data of local earthquakes. Our results show that the fast polarization directions in the upper crust have spatial variations across the region of the earthquake that are likely caused by both structural and stress field effects. The northwest–southeast direction near the northeastern end of the source zone (beneath station N.NGOH) and the east–west direction to the southwest (beneath station N.KWNH) are consistent with the spatial variation of the orientation of the maximum compression of the local stress field. Fast polarization directions at other stations tend to align in the directions of active faults and folds and thus are considered to be structure induced. These spatial patterns were unaffected by the earthquake. However, at two stations (N.NGOH and N.KWNH) we observe an increase in both the average and scatter of the normalized delay times (δt) during the aftershock period. In addition, two stations (HIROKA and N.YNTH) that are located in the strike‐normal direction east of the source area show an increase in the average of the normalized δt and a rotation of up to 90° of the fast direction immediately after the mainshock. We also notice that stations located very close to the source fault (DP.YMK and DP.OJK) show larger average delay times compared with stations farther away (HIROKA and N.YNTH) during the postseismic stage. To explain the temporal changes in the strength of the anisotropy, we speculate that spatiotemporal variations in microcrack development in and around the source area could be caused by static stress changes due to tectonic deformation and the earthquake rupture.

scholarly journals Traces of the crustal units and the upper-mantle structure in the southwestern part of the East European Craton

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 821-836 ◽  
Author(s):  
I. Janutyte ◽  
E. Kozlovskaya ◽  
M. Majdanski ◽  
P. H. Voss ◽  
M. Budraitis ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Synthetic Data ◽  
Velocity Model ◽  
East European Craton ◽  
P Wave ◽  
Seismic Velocities ◽  
P Waves ◽  
Data Set ◽  
Teleseismic Tomography ◽  
East European

Abstract. The presented study is a part of the passive seismic experiment PASSEQ 2006–2008, which took place around the Trans-European Suture Zone (TESZ) from May 2006 to June 2008. The data set of 4195 manually picked arrivals of teleseismic P waves of 101 earthquakes (EQs) recorded in the seismic stations deployed to the east of the TESZ was inverted using the non-linear teleseismic tomography algorithm TELINV. Two 3-D crustal models were used to estimate the crustal travel time (TT) corrections. As a result, we obtain a model of P-wave velocity variations in the upper mantle beneath the TESZ and the East European Craton (EEC). In the study area beneath the craton, we observe up to 3% higher and beneath the TESZ about 2–3% lower seismic velocities compared to the IASP91 velocity model. We find the seismic lithosphere–asthenosphere boundary (LAB) beneath the TESZ at a depth of about 180 km, while we observe no seismic LAB beneath the EEC. The inversion results obtained with the real and the synthetic data sets indicate a ramp shape of the LAB in the northern TESZ, where we observe values of seismic velocities close to those of the craton down to about 150 km. The lithosphere thickness in the EEC increases going from the TESZ to the NE from about 180 km beneath Poland to 300 km or more beneath Lithuania. Moreover, in western Lithuania we find an indication of an upper-mantle dome. In our results, the crustal units are not well resolved. There are no clear indications of the features in the upper mantle which could be related to the crustal units in the study area. On the other hand, at a depth of 120–150 km we indicate a trace of a boundary of proposed palaeosubduction zone between the East Lithuanian Domain (EL) and the West Lithuanian Granulite Domain (WLG). Also, in our results, we may have identified two anorogenic granitoid plutons.

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