Abstract

During the last stages of the Weichselian glaciation (15,0009,000 years B.P.), the reduction of ice loads induced a rapid uplift in Fennoscandia. This resulted in an active faulting of the bedrock in northern Fennoscandia with the occurrence of large magnitude earthquakes (Mw > 6.0) within the Lapland fault province (LFP). The northernmost known faults within the occur within the Stuoragurra fault complex (SFC), located in the Troms and Finnmark county. The fault line is relatively continuous for 90 km with a maximum displacement of 10 meters and a maximum scarp height of 7 meters. C. 30 faults segments have been grouped into three separate fault systems that were formed between about 600 and 4,000 years before present. The seismic records reported by the Norwegian National Seismic Network (NNSN) and the Norwegian Seismic Array (NORSAR) from 1900 until today, show low seismicity in the area. However, a major earthquake presumed to have occurred with Mw =7.0 less than 600 years ago along the central section of the SFC, makes it necessary to revisit the seismic recordings and to review and reassess any potential seismic risk in the area. Nowadays, the advances in the automatic detection of arrival times in seismic signals are making possible to revisit historical records and to obtain more complete seismic catalogs in short time. In this work we present both, a review and an improvement of the existing historical seismic catalogs around to Stuoragurra fault. We first downloaded all the existing open waveform data in the area from different datacenters (GEOFON, IRIS, ORFEUS, REFIS and UIB-NORSAR), covering the period between the years 2007-2020. Then, we used the Regressive ESTimator (REST) autopicking algorithm described in Comte et el. (2019) to create a new possible catalog of earthquakes in the area. We carefully checked all the obtained earthquakes, discarding the incorrect signals to generate an update catalog; preliminary results show an improvement of about 25% more detected earthquakes than the original catalog. This result provides new and relevant information which can be used for the re-assessment of the seismic hazard in the Stuoragurra fault complex and the surrounding area, being then highly beneficial for the construction of hydropower dams, petroleum facilities and other infrastructure.