Palaeoseismic Deformations in the Eastern Baltic Region (Kaliningrad District of Russia)

Estonian Journal of Earth Sciences, 2017, 66, 3, 119–129 https://doi.org/10.3176/earth.2017.09 Palaeoseismic deformations in the Eastern Baltic region (Kaliningrad District of Russia) Olga Druzhininaa, Albertas Bitinasb, Anatoly Molodkovc and Tatyana Kolesnika a I. Kant Baltic Federal University, A. Nevsky St. 14, Kaliningrad, 236041, Russia; [email protected], [email protected] b Klaipėda University, 84 H. Manto St., Klaipėda LT-92294, Lithuania; [email protected] c Department of Geology, School of Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia; [email protected] Received 12 October 2016, accepted 10 March 2017, available online 8 June 2017 Abstract. The article presents new data on sedimentological structures, which have been discovered at the Ryadino archaeological excavation in the northeast of the Kaliningrad District of Russia (the Šešupė River Valley). Tongue-shaped and dome- shaped diapir-like structures indicate liquefaction-induced features. As the most plausible reason, the earthquake-induced shaking is discussed. A preliminary estimation of the time interval for the seismic event covers the period from the early up to the late Holocene. The reasons for seismic activity in this region can be related to neotectonic movements (including glacio-isostatic rebound) as recorded in the southeastern Baltic Sea area of the Fennoscandian ice sheet margin zone. The relation between a palaeoseismic event and the essential changes in the hydrographic network in the region is also discussed. Key words: palaeoseismicity, liquefaction, soft-sediment deformation structures, glacio-isostatic rebound, Šešupė River valley. INTRODUCTION According to Stewart et al. (2000) and Sandersen & Jørgensen (2015), the loading and unloading of ice Palaeoseismological investigations have a long tradition sheets, which covered large areas of northern Europe, in many European regions affected by glaciations. can affect areas hundreds of kilometres outside the former Successful attempts have been made in studies aimed at ice-sheet margins and the areas that could potentially be extending the seismic catalogues, identifying the causes affected by deglaciation tectonics. These areas may of recent and past seismic activity, estimating the therefore have considerable size and include wide maximum possible magnitudes, earthquake recurrence territories from the British Isles to the Baltic region and intervals, etc. (Mörner 1985, 2003, 2011; Stewart et al. further to the east. 2000; Hoffmann & Reicherter 2012; Nikonov 2013; Van High seismic activity in the Fennoscandian shield Loon & Pisarska-Jamroźy 2014; Sandersen & Jørgensen area and the adjacent Baltic Sea territories (including 2015; Grützner et al. 2016; Van Loon et al. 2016). evidence of tsunamis in the Baltic Sea) during the Most of the palaeoseismic events identified are dated late glacial and the Holocene has been documented to the late Pleistocene and early Holocene and have led in a number of studies (e.g. Mörner 2003, 2011, 2013; to a conclusion about the relationship existing between Nikonov 2004; Bitinas & Lazauskienė 2011; Bitinas 2012; postglacial rebound and seismic activity (Stewart et al. Mörner & Dawson 2012; Rotnicki et al. 2016). Seismic 2000; Mörner 2003; Houtgast et al. 2005). The Fenno- activity in the Eastern Baltic Sea region (including Baltic scandian postglacial rebound and glacial forebulge in states and Kaliningrad District of Russia) is significantly relation to the underlying tectonic stress have engendered lower than the seismicity in the Fennoscandian shield. a pattern of alternating regions of higher and lower Nevertheless, a considerable number (>40) of seismic seismicity, whereas evidences of active faulting and events with magnitudes (M) up to 5, including those, seismicity are mostly connected to the areas where ice which produced surface ruptures, have been recorded in sheets reached their maximum thickness, including the the area (Nikonov 2008a, 2008b; Bitinas & Lazauskienė marginal regions (Mörner 2003; Steffen & Wu 2011; 2011; Van Loon et al. 2016). Historical data on earth- Hoffmann & Reicherter 2012; Brandes et al. 2015). quakes on the territories of former Prussia (1302) and © 2017 Authors. This is an Open Access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International Licence (http://creativecommons.org/licenses/by/4.0). 119 Estonian Journal of Earth Sciences, 2017, 66, 3, 119–129 Lithuania (1328) both with M ~5, Latvia (in 1616, M 4.8), deformations. Such structures have been found and a tsunami event in 1779 on the Baltic Sea coast near described in a number of locations in Estonia, Latvia, Trzebiatów (Poland), recent earthquakes in Estonia Lithuania, Poland and Belarus. The majority of these (in 1976, M 4.78) and the Kaliningrad District (Russia) seismite-type structures were formed during the late (in 2004, M 5.2) provide evidence of seismic activity in glacial and Holocene periods, and several of them are this part of Subbalticum (Nikonov 2008a, 2008b, 2010). related to the middle Pleistocene, Eemian interglacial Palaeoseismological studies of the Eastern Baltic and early Weichselian strata (Bitinas & Lazauskienė area have a relatively short history. However, recent 2011; Bitinas 2012; Van Loon & Pisarska-Jamroźy 2014; detailed analysis of the Quaternary deposits of this Van Loon et al. 2016). territory based on modern state-of-the-art palaeo- The territory of the Kaliningrad District (Fig. 1) was seismology has led to considerable advancements in for many years considered as seismically inactive, the understanding of some important aspects of regional and no evidence of palaeoseismicity has been recorded seismic geology. Many of the soft-sediment deformed before 2004. The situation changed after the Kaliningrad structures (SSDS), earlier interpreted as cryoturbations, earthquake in 2004 with М 5.2, which led to the glaciotectonic features or so-called water-escape destruction of 1046 buildings and surface ruptures structures, could be the liquefaction-induced sediment (Nikonov 2010). The location of the causative faults is Fig. 1. A, location of the study area; B, the geological and geomorphological situation at the Ryadino archaeological site and its surroundings (after Bitinas et al. 2017). 120 O. Druzhinina et al.: Palaeoseismic deformations in the Eastern Baltic disputable, but could probably be related to two zones at GEOLOGICAL SETTING a depth of about 20 km: a meridional active fault along the western coast and a latitudinal one along the northern The Eastern Baltic area belongs to the Baltic syncline coast of the Sambian Peninsula (Nikonov 2008a, 2010) in the west of the East European Platform. After the (Fig. 2). The earthquake of 2004 gave an impulse to deglaciation, during the late Pleistocene and Holocene, investigations of recent and historical seismicity in the the southeastern part of the Baltic Sea region (vicinity region. A number of SSDS, interpreted as palaeoseismic of Klaipėda) was uplifting due to glacio-isostatic rebound deformations, have been identified and described in at a rate of up to 6.8 mm per year, whereas at the several locations in the Sambian Peninsula. On the new present time the subsidence up to 0.5–2.0 mm per year map of seismic activity published in 2013, the Eastern is prevailing (Šliaupa et al. 2005). Recent studies of Baltic region is shown as one of the seismically most Holocene vertical crustal movements have revealed that active regions of the East European Plain (Nikonov 2013). against the background of the overall subsidence of the The present article provides new data on SSDS Baltic syncline there exist several stable or slightly demonstrating the liquefaction features, which were uplifting blocks, probably followed by active faults – identified in the northeast of the Kaliningrad District of the Łeba, Sambian and Klaipeda tectonic blocks (Aizberg Russia (the Šešupė River Valley) during the archaeo- et al. 2001; Nikonov et al. 2009). logical excavation of the Ryadino Palaeolithic site in The study area is located at the confluence of the 2009–2010 (Fig. 1). The goal of this study is to link the Šešupė and the Neman rivers. The present relief and the inferred liquefaction structures to a palaeoseismic event uppermost part of the sediments were formed at the very and to contribute to the understanding of the palaeo- end of the last (Weichselian) glaciation (Fig. 1). seismicity of the area under consideration in the context According to geological-geomorphological data, part of regional and continental tectonic history. of the Šešupė River valley was a part of the main channel Fig. 2. Map showing the main tectonic faults on the territory of the Kaliningrad District (Russia), Lithuania and Poland (after Aizberg et al. 2001). 121 Estonian Journal of Earth Sciences, 2017, 66, 3, 119–129 for meltwater discharge from north to south, and further carried out by the X-ray fluorescence method using to the west, along the valley of the present-day Pregolya a SPECTROSCAN-MAKC spectrometer. Statistical River, during the final stage of the Weichselian glaciation processing was performed using Statistica 6.0 software. (Guobytė & Jusienė 2007; Bitinas et al. 2017). It Fine-grained fraction (0.25–0.50 mm) was used for happened when large territories of Lithuania and the the reconstruction of palaeoenvironmental conditions by Kaliningrad District were partly deglaciated, but the using the geochemical

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