Abstract. The Sami word ráhppát means rough bouldery/stony terrain with sharp-relief topography in Finnmark, northern Norway. Ráhppát is a common name in the region of the Younger Dryas landforms, yet the origin of ráhppát has remained obscure. The timing of the Younger Dryas is concomitant with the maximum neotectonic fault instability in Fennoscandia. Hence, earthquake activity may have been one of the contributing factors for the Younger Dryas morphologies. Ráhppát on the Maskevarri fell, classified as a part of Tromsø-Lyngen sub-stage of the Younger Dryas, was studied by means of geomorphology and measurements of electrical-sedimentary anisotropy. Ráhppát was found to be built up of an anastomosing network of stony eskerlike ridges and mounds bordered with arch-shaped and sinusoidal ridges. These bordering ridges exhibit sedimentary (azimuthal soil electrical conductivity) anisotropy parallelto-ridge trends and were interconnected to meltwater gullies suggesting generation through short-lived conduit infills. We did not find electrical-sedimentary evidence to support the concept of englacial thrusting and/or compression, often described for Younger Dryas moraines. Maskevarri Ráhppát is typified by ∼ 500 ponds and small lakes on three different elevations descending in an up-ice direction. These may have generated through late glacial earthquake(s) also contributing to subglacial deformation of Maskevarri Ráhppát.
The cyclic nature of glaciations and related postglacial faulting represents a risk for the deep geological disposal of spent nuclear fuel in areas likely to be affected by future glaciations. Seismic history was therefore studied by means of detecting geomorphological structures on airborne laser scanning digital elevation models and underground by excavating in an esker and trenching across a postglacial fault located in northern Fennoscandia. OLS dating and assessing the geomorphological structures was used for timing of the seismic history. The results suggest that the faulting of different segments in the Pasmajärvi complex is due to at least two late Weichselian events, which probably occurred both subglacially and postglacially. The most reliable input for the moment magnitude estimates was vertical slip profiles, and therefore these estimates (MW ≈ 6.4–6.9) are suggested. © 2020 John Wiley & Sons, Ltd.
Abstract. The Sami word ráhppát means rough bouldery/stony terrain with sharp-relief topography in Finnmark, North Norway. Ráhppáts are common features in the region of the Younger Dryas landforms, yet their origin has remained obscure. The timing of the Younger Dryas is concomitant with the maximum neotectonic fault instability in Fennoscandia, hence earthquake activity was one of the contributing factors for the Younger Dryas morphologies. Ráhppát on the Maskevarri fell, classified as a part of Tromsø-Lyngen sub-stage of the Younger Dryas, was studied by means of geomorphology and measurements of electrical-sedimentary anisotropy. Ráhppát was found to be built up of a network of stony ridges and mounds on fell terraces bordered with arch-shaped and sinusoidal ridges. These bordering ridges exhibit sedimentary (azimuthal soil electrical conductivity) anisotropy parallel-to-ridge trends and were interconnected to meltwater gullies suggesting generation through short-lived conduit infills. We did not find electrical-sedimentary evidence to support the concept of englacial thrusting and/or compression, often described for Younger Dryas moraines. Maskevarri Ráhppát is typified by ~ 500 ponds and small lakes on three different terrace elevations descending in an up-ice direction. These escarpments may have generated trough late glacial earthquake(s) contributing to subglacial deformation of Maskevarri Ráhppát.
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