Seismodeformations in Late Holocene estuary deposits in the central part of St. Petersburg

Abstract

Deformations in a section of layered Late Holocene estuary-flood plain deposits, found for the first time in the central part of St. Petersburg, are discussed. The discussed reason why this section could have been deformed inside the undeformed stratum is a horizontally directed dynamical shock. The probable causes of deformation are considered, with the most real one being a relatively distant earthquake. An attempt is made to estimate the intensity of this quake for the territory of the city.

The active tectonics of the Vuoksi Fault Zone in the Karelian Isthmus: parameters of paleoearthquakes estimated from bedrock and softsediment deformation features

“…The late-and post-glacial fragmentation of rocks and the deformation of glacial, lacustrine and alluvial sediments was presumably the cause of large earthquakes as described by researchers for different localities in the western part of the Fennoscandian crystalline shield (Kujansuu, 1964;Lundqvist & Lagerbäck, 1976;Bungum & Lindholm, 1997;Kuivamäki et al, 1998;Mörner, 1985Mörner, , 2003Mörner et al, 2003;Olesen et al, 1992;Sjöberg, 1994;Lagerbäck & Sundh, 2008;Kukkonen et al, 2011). Similar studies were carried out for the eastern Fennoscandia, which consists of Russian Karelia, the Kola Peninsula, and the Karelian Isthmus (Lukashov, 1995(Lukashov, , 2004Nikonov & Zykov, 1996;Zykov, 2001;Nikolaeva, 2006;Nikonov, 2008;2012;Nikonov et al, 2014;Nikonov & Shvarev, 2015;Nikolaeva et al, 2017;Shvarev & Rodkin, 2018). Some locations of paleoearthquakes are undisputable large post-glacial faults tens of kilometres long with displacements of some meters.…”