The 90-km long Stuoragurra Fault Complex, part of the approximately 4–5-km wide Precambrian Mierojávri–Sværholt Shear Zone, constitutes the Norwegian part of the larger Lapland province of postglacial faults. It consists of three separate fault systems being 6–12 km apart. The faults dip 30–75° to the SE and can be traced to about 500 m depth. Deep seismic profiling shows that the shear zone dips at an angle of about 43° to the southeast and can be traced to about 3 km depth. A total of approximately 80 earthquakes were registered here between 1991 and 2019. Most of them occurred to the southeast of the fault scarps. The maximum moment magnitude was 4.0. The formation of postglacial faults in northern Fennoscandia has previously been associated with the deglaciation of the last inland ice. Dating of fault reactivation reveals, however, a late Holocene age (between around 700 and 4000 a BP). The reverse displacement of around 9 m and fault system lengths of 14 and 21 km of the two southernmost fault systems indicate a moment magnitude of about 7. The results from this study indicate that the expected maximum magnitude of future earthquakes in Fennoscandia is about 7.

This chapter reviews the results of studies of late- and postglacial faults in the Russian part of the Fennoscandian Shield (Kola Peninsula, Karelia, Sankt-Petersburg region). It provides a brief overview and description from north to south of the main seismic lineaments (Murmansk and Kandalaksha) as well as results from a study of some secondary lineaments, individual late- and postglacial faults and seismic dislocations. The obtained data allowed defining a decrease in seismic activity from the Late Glaciation to the present times. It is due to the fading glacial isostatic uplift of the shield and the change of the leading role from the vertically directed forces of glacial isostasy to horizontal compressive strains. Glacial isostasy as a factor giving rise to stresses has nearly exhausted itself by the present time, while the tectonic factor continues to be felt.

Postglacial faults in northern Fennoscandia have been investigated through geophysical methods, trenching, and mapping of brittle deformation structures. Very little is known about postglacial faults through direct measurements. A few short, up to 500 m deep, boreholes exist. Plans for a scientific drilling program were initiated in 2010. The drilling target has been identified: The Pärvie Fault system is the longest known postglacial fault in the world and has been proposed to have hosted an M8 earthquake near the end or just after the last glaciation. Further, this fault system is still microseismically active. The drill sites are north of the Arctic Circle, in a sparsely populated area. Existing site survey data, established logistics, and societal relevance through the fault’s proximity to mining and energy operations make this fault system an appropriate target. The International Continental Scientific Drilling Program approved a full drilling proposal in October 2019. This chapter presents an abbreviated version of the approved proposal.

Glacially triggered faulting, also called glacially induced faulting or postglacial faulting, describes fault movement caused by a combination of tectonic and glacially induced isostatic stresses. Stresses induced by the advance and retreat of an ice sheet are thought to be released during or after ice melting and reactivate pre-existing faults. The most impressive fault scarps that witness such activity, are found in Northern Europe. It was assumed these features are unique. This view has changed recently as new faults were discovered – even outside the former glaciated area – and fault activity dating showed several phases of reactivation thousands of years after deglaciation ended. This book summarizes the research until the very recent findings. It reviews the theoretic aspects, i.e. the knowledge to understand the presence of glacially induced fault structures, followed by an overview of geological, geophysical, geodetic and geomorphological investigations methods, a summary of all known glacially induced faults worldwide and an outline for modelling of these stresses and faults.

This chapter investigates the Fennoscandian uplift area since the latest Ice Age and addresses the question if glacial isostatic adjustment may influence current seismicity. The region is in an intraplate area, with stresses caused by the lithospheric relative plate motions. Discussions on whether uplift and plate tectonics are the only causes of stress have been going on for many years in the scientific community.

This review considers the improved sensitivity of the seismograph networks, and at the same time attempts to omit man-made explosions and mining events in the pattern, to present the best possible earthquake pattern. Stress orientations and their connection to the uplift pattern and known tectonics are evaluated. Besides plate motion and uplift, one finds that some regions are affected stress-wise by differences in geographical sediment loading as well as by topography variations. The stress release in the present-day earthquakes shows a pattern that deviates from that of the time right after the Ice Age. This chapter treats the stress pattern generalized for Fennoscandia and guides the interested reader to more details in the national chapters.

Numerous methods have been applied to dating postglacial faults in Fennoscandia. Traditionally, these range from determining relative ages based on cross-cutting relationships to determining absolute ages based on stratigraphy and radiocarbon dates. More recently, however, direct dating of fault scarps using terrestrial cosmogenic nuclide dating has been attempted.

The benefits and limitations of these methods are described citing examples from recent literature. Subsequently, the dates themselves are discussed in the context of the longstanding hypothesis that postglacial faults in Fennoscandia ruptured only once during or shortly after deglaciation. While each of the studies reviewed applies only to the investigated faults, collectively recent literature indicates a longer lasting and more complex spatial and temporal history of postglacial faulting in the Fennoscandian Shield area.

Using information from airborne light detection and ranging (LiDAR) data has produced a breakthrough in identification of postglacial faults and earthquake-deformed Quaternary deposits. LiDAR digital elevation models (DEMs) also improve the collection of detailed information on their spatial distribution, characteristics and geometry, and provides guidance for the more costly and time-consuming field studies. In areas of weak glacial erosion, younger and older (i.e. Pre-Late Weichselian) ruptures have been discovered superimposed on the same or adjacent postglacial fault segments, as has been identified when combining the DEM information and test pit sedimentological studies. We discuss Finnish examples and identify advantages, disadvantages and limitations. Advantages include verification of previously known fault scarps, detection of new postglacial fault segments, systems and entire complexes and the ability to measure the dimensions (lengths and offset) of the fault scarps from the LiDAR DEM data. Disadvantages include that inventory of the sub- and postglacial fault scarps is only possible when linear scarps cross-cut glacial and postglacial sediments.