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Electrical-sedimentary anisotropy of landforms adjacent to postglacial faults in Lapland

Sutinen, Raimo, Hyvönen, Eija, Liwata-Kenttälä, Pauliina, Middleton, Maarit, Ojala, Antti, Ruskeeniemi, Timo, Sutinen, Aleksi, Mattila, Jussi
Geomorphology 2019 v.326 pp. 213-224
anisotropy, deformation, earthquakes, geophysics, glaciers, isotropy, lidar, liquefaction, radioactive waste, sediments, transportation, Finland, Lapland, Scandinavia
Postglacial faults (PGFs) are common SW-NE-trending features in the northern part of the Fennoscandian shield being attributed to former high-magnitude (Mw ≈ 7–8.2) earthquakes (Arvidsson, 1996). These are of interest for the long-term seismic hazard of deep geological nuclear waste repositories. The PGFs are still seismically active; and many of the deformation features, such as paleolandslides, are spatially coextensive within these earthquake zones. Based on the 14C-datings of landslide-buried organic materials, three postglacial seismic episodes (≈9.7–11, ≈5–6, and 1.3–1.8 ky ago) have been found in western Finnish Lapland. Because the model predictions by Wu et al. (1999) suggested that the onset of fault instability started at 15 ky and that the maximum fault instability was reached at 13–10 ky in Fennoscandia, we postulate that not only subaerial but also subglacial types of deformations may have been associated with the past seismic events. Here, we present LiDAR DEM observations and sediment electromagnetic anisotropy data on the landforms, such as the rim-ridged/arcuate Pulju moraine (Kujansuu, 1967), roundish (liquefaction) bowls, postdepositional (liquefaction) deformations on streamlined landforms, as well as hummocky ridge fields of massflow sediments. The sediments in the Pulju moraine and massflow ridges displayed clear anisotropy, indicating lateral transportation in subglacial wet-based environment. Instead, sediments in the bowl-shaped morphologies next to PGFs and deformed ice-stream flutings tended to be isotropic, suggesting postdepositional and vertical liquefaction processes. Based on the LiDAR morphology and sedimentary anisotropy data, these landforms may be linked to past earthquakes.