Distribution and morphology of landslides in northern Finland: An analysis of postglacial seismic activity

Abstract

The ages and sizes of landslides occurring in seismically active areas can be used to reconstruct the seismic history of the area and estimate the maximum moment magnitudes of past earthquakes. Here, we present a data set of 121 landslides discovered in northern Finland that were analyzed for their morphometric characteristics. We show that 89 debris slide type landslides in the data set are clustered close to known postglacial faults (PGFs) and thus provide information on the characteristics of postglacial paleoseismic events. By using empirical correlations between the landslide volume–area data and earthquake moment magnitude, we estimate maximum moment magnitudes Mw≈6.9–7.7 for postglacial earthquakes in the Suasselkä, Isovaara–Riikonkumpu, Venejärvi, and Vaalajärvi areas, where earlier estimates based on fault length and displacement have yielded magnitudes varying between Mw≈6.5 and 7.5. We also show that the landslides in northern Finland are located within a radius of 35km from the closest known PGF and that sizes of the landslides decrease as a function of distance from PGFs, hence providing strong empirical evidence for their seismic origin. As far as we are aware, this is the first use of landside data in quantifying postglacial seismicity within the Fennoscandian Shield area.