TTZ-South seismic experiment

T Janik,T Amashukeli,A Murovskaya,A Tolkunov,S Chulkov,T Yegorova,A G Łuszyński,D Wójcik,O Legostaeva,V Omelchenko,D Gryn,P Środa,V Starostenko,W Czuba,J Mechie,K Kolomiyets,K Zajats,P Aleksandrowski,D Lysynchuk

doi:10.24028/gzh.0203-3100.v42i3.2020.204698

Abstract

The wide-angle reflection and refraction (WARR) TTZ-South transect carried out in 2018 crosses the SW region of Ukraine and the SE region of Poland. The TTZ-South profile targeted the structure of the Earth’s crust and upper mantle of the Trans-European Suture Zone, as well as the southwestern segment of the East European Craton (slope of the Ukrainian Shield). The ~550 km long profile (~230 km in Poland and ~320 km in western Ukraine) is an extension of previously realized projects in Poland, TTZ (1993) and CEL03 (2000). The deep seismic sounding study along the TTZ-South profile using TEXAN and DATA-CUBE seismic stations (320 units) made it possible to obtain high-quality seismic records from eleven shot points (six in Ukraine and five in Poland). This paper presents a smooth P-wave velocity model based on first-arrival travel-time inversion using the FAST (First Arrival Seismic Tomography) code. The obtained image represents a preliminary velocity model which, according to the P -wave velocities, consists of a sedimentary layer and the crystalline crust that could comprise upper, middle and lower crustal layers. The Moho interface, approximated by the 7.5 km/s isoline, is located at 45—47 km depth in the central part of the profile, shallowing to 40 and 37 km depth in the northern (Radom-Łysogory Unit, Poland) and southern (Volyno-Podolian Monocline, Ukraine) segments of the profile, respectively. A peculiar feature of the velocity cross-section is a number of high-velocity bodies distinguished in the depth range of 10—35 km. Such high-velocity bodies were detected previously in the crust of the Radom-Łysogory Unit. These bodies, inferred at depths of 10—35 km, could be allochthonous fragments of what was originally a single mafic body or separate mafic bodies intruded into the crust during the break-up of Rodinia in the Neoproterozoic, which was accompanied by considerable rifting. The manifestations of such magmatism are known in the NE part of the Volyno-Podolian Monocline, where the Vendian trap formation occurs at the surface.

Highlights

IntroductionThe TTZ-South experiment is the latest in a series of three wide-angle reflection/refraction (WARR) seismic studies situated along a NW-SE oriented line in Central Europe
This paper presents a smooth P-wave velocity model based on first-arrival travel-time inversion using the FAST (First Arrival Seismic Tomography) code
A peculiar feature of the velocity cross-section is a number of high-velocity bodies distinguished in the depth range of 10—35 km

Summary

Introduction

The TTZ-South experiment is the latest in a series of three wide-angle reflection/refraction (WARR) seismic studies situated along a NW-SE oriented line in Central Europe. TTZ-South profile that runs along the southwestern edge of the East European Craton in southeastern Poland and western Ukraine. The main purpose of these WARR studies was to determine the Earth’s crustal and upper mantle structure along the Teisseyre-Tornquist (TTZ) zone in southeastern Poland and western Ukraine (Fig. 1). Studies of the tectonic structure in the area of the junction of the EEC with the accreted terranes of the West European Platform of mainly Palaeozoic age are extremely important for understanding the geodynamic processes that have formed the structure of the lithosphere in this region. In the late Riphean—Early Vendian, during the break-up of the Rodinia supercontinent, the rifted margin of the EEC and an extensive system of aulacogens was formed, including the VolhyniaOrsha aulacogen It forms a zone of structural heterogeneity at the border of Sarmatia and Fennoscandia. Locations and parameters of explosive sources used along the TTZ-South profile

Number of boreholes

Conclusions