Strong Earthquake of February 18, 1772, on the West Murman Coast: Tectonic Disposition, Natural Deformations, and Novel Estimates of the Source Parameters

Abstract

This article, continuing the study of the powerful event of February 18, 1772, on the northern Kola Peninsula according to written sources about it (Nikonov, 2020a), provides materials and analyzes several groups of natural processes in the epicentral and adjacent areas in terms of natural manifestations of seismic disturbances with arguments in favor of their occurrence as result of the earthquake of February 18, 1772. The groups include materials of a geophysical profile-section along the seafloor north of the Cape Pogan-Navolok, changes in the nature of new accumulations of debris at the bottom along the Murman Coast west of Cape Pogan-Navolok, in the area on the eastern coast of Kola Bay. Signatures of seismic disturbances in all groups are quite consistent with the event of 1772 and, thus, allow an increase in the shaking intensity score by VI–VII points independent of written data (in the 2020 article there were only two points: the settlement of Kola and cape Pogan-Navolok at the NW outlet of Kola Bay. On this basis, the source parameters of the event are determined anew. In addition, some features of the new tsunami at the outlet of Ura Bay to the Barents Sea are considered. The earthquake of February 18, 1772, according to the set of revealed signatures, is recognized as the most powerful of the currently known historical earthquakes in the Murmansk seismogenic zone, which is today acknowledged as a higher-order seismically active zone.