Evidence for postglacial seismicity in lacustrine records in the western Kola Peninsula (north-western Russia)

Abstract

In this article we describe and interpret disturbances in the sedimentary records of four lakes on the western flank of Lake Imandra (NE Fennoscandia, Kola Peninsula). The research framework comprises sedimentological and textural criteria for a visual description of sedimentary structures sediment core data, chronological (radiocarbon dating) data, and ground-penetrating radar (GPR) data. Disturbances preserved in lake sequences contain a mixture of chaotic fragments of sand, silt, polychromatic gyttja, peat, and wood fragments embedded in the organogenic matrix. The synchronicity of disturbances, fast sediment accumulation in lakes, relationship with Quaternary faults, the observed mass movements in lake sediments are interpreted as potential consequences of the earthquake shaking. A seismic event with a magnitude Mw no less than 4.5–5 and intensity of shaking I0 = IV–VI took place in the Middle Holocene, 6400–6100 cal. yr BP. Our studies show that although this area is not seismically active today, some of the main fault zones experienced short periods of reactivation also in the postglacial time, when glacioisostatic rebound after the ice retreat was already very low.