Postglacial Faulting in Norway

Olesen, Odleiv; Olsen, Lars; Gibbons, Steven J.; Ruud, Bent Ole; Høgaas, Fredrik; Johansen, Tor Arne; Kværna, Tormod

doi:10.1017/9781108779906.015

Cited by 6 publications

(6 citation statements)

References 34 publications

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“…Once established, profound zones of weakness have a well-documented capacity for reactivation, even in cases where the secondary stress situation is different from the primary one. Accordingly, such zones tend to remain active over long geological time spans [9,26,75,98,110,135,136], accumulating varying types of fault rocks and fracture systems such that originally deepseated, high pressure-temperature, quasi-plastic deformation products become overprinted by brittle structures generated at shallower levels of burial [136][137][138]. High-resolution chronological work is crucial in the documentation of such developments (e.g., [78,92]) and therefore needs to be included in the database on such structural elements.…”

Section: Discussionmentioning

confidence: 99%

“…It is marked by a more than 100 m-wide low-resistivity zone, probably reflecting fracturing in the footwall and hanging wall of the fault. Radiocarbon dating has shown that the largest earthquake along the Stuoragurra Fault Complex occurred less than 500 years ago [98,110]. The recurrence interval of large earthquakes in intraplate regions like Norway can be several hundred years or even longer.…”

Section: Dynamic Lineament Analysismentioning

confidence: 99%

“…Holocene reactivation of ancient faults (e.g., the Stuoragurra Fault Complex) can be studied by trenching across fault scarps. Radiocarbon dating of organic matter located in buried and severely deformed sediment horizons provides reliable ages for the maximum age of faulting [98,110].…”

Section: Technical Presumptions and Requirements In Lineament Analysismentioning

confidence: 99%

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The Concept of Lineaments in Geological Structural Analysis; Principles and Methods: A Review Based on Examples from Norway

Gabrielsen,

Olesen

2024

Geomatics

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Application of lineament analysis in structural geology gained renewed interest when remote sensing data and technology became available through dedicated Earth observation satellites like Landsat in 1972. Lineament data have since been widely used in general structural investigations and resource and geohazard studies. The present contribution argues that lineament analysis remains a useful tool in structural geology research both at the regional and local scales. However, the traditional “lineament study” is only one of several methods. It is argued here that structural and lineament remote sensing studies can be separated into four distinct strategies or approaches. The general analyzing approach includes general structural analysis and identification of foliation patterns and composite structural units (mega-units). The general approach is routinely used by most geologists in preparation for field work, and it is argued that at least parts of this should be performed manually by staff who will participate in the field activity. We argue that this approach should be a cyclic process so that the lineament database is continuously revised by the integration of data acquired by field data and supplementary data sets, like geophysical geochronological data. To ensure that general geological (field) knowledge is not neglected, it is our experience that at least a part of this type of analysis should be performed manually. The statistical approach conforms with what most geologists would regard as “lineament analysis” and is based on statistical scrutiny of the available lineament data with the aim of identifying zones of an enhanced (or subdued) lineament density. It would commonly predict the general geometric characteristics and classification of individual lineaments or groups of lineaments. Due to efficiency, capacity, consistency of interpretation methods, interpretation and statistical handling, this interpretative approach may most conveniently be performed through the use of automatized methods, namely by applying algorithms for pattern recognition and machine learning. The focused and dynamic approaches focus on specified lineaments or faults and commonly include a full structural geological analysis and data acquired from field work. It is emphasized that geophysical (potential field) data should be utilized in lineament analysis wherever available in all approaches. Furthermore, great care should be taken in the construction of the database, which should be tailored for this kind of study. The database should have a 3D or even 4D capacity and be object-oriented and designed to absorb different (and even unforeseen) data types on all scales. It should also be designed to interface with shifting modeling tools and other databases. Studies of the Norwegian mainland have utilized most of these strategies in lineament studies on different scales. It is concluded that lineament studies have revealed fracture and fault systems and the geometric relations between them, which would have remained unknown without application of remote sensing data and lineament analysis.

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Section: Discussionmentioning

confidence: 99%

Section: Dynamic Lineament Analysismentioning

confidence: 99%

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The Concept of Lineaments in Geological Structural Analysis; Principles and Methods: A Review Based on Examples from Norway

Gabrielsen,

Olesen

2024

Geomatics

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“…The inference that the last 20 years of earthquake data in northern Sweden indicates that the area has high seismic hazard is interesting in the light of recent work on the PGFs in the region. Smith et al (2021) found repeated ruptures on the Lainio PGF, with the latest recurring after deglaciation, and (Olesen et al, 2021) identified ruptures of magnitude 7 as recently as 700 years ago on the Stuoragurra fault in northern Norway. Taken together, all observations suggest that seismic hazard should be taken into careful consideration in the region, especially since the region is home to major mining operations, large hydroelectric power dams and an increasing number of wind energy installations.…”

Section: Discussionmentioning

confidence: 99%

“…Such large events have been inferred to be triggered by the glacial isostatic stress contribution from the late deglacial phase (e.g. , but as the recent trenching of the Stuoragurra fault in northern Norway indicate ruptures of magnitude 7 as late as 700 years ago (Olesen et al, 2021), the potential for very large earthquakes in the current stress field needs to be considered.…”

Section: Maximum Magnitudementioning

confidence: 99%

Probabilistic Seismic Hazard Assessment of Sweden

Joshi,

Lund,

Roberts

2023

Preprint

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Abstract. Assessing seismic hazard in stable continental regions (SCR) such as Sweden poses unique challenges compared to active seismic regions. With diffuse seismicity, low seismicity rate, few large magnitude earthquakes and little strong motion data, estimating recurrence parameters and determining appropriate attenuation relationships is challenging. This study presents a probabilistic seismic hazard assessment of Sweden based on a recent earthquake catalogue which includes a large number of events with magnitudes ranging from 5.9 to -1.4, enabling recurrence parameters to be calculated for more source areas than in previous studies, and with less uncertainty. Recent ground motion models developed specifically for stable continental regions, including Fennoscandia, are used in logic trees accounting for their uncertainty and the hazard is calculated using the OpenQuake engine. The results are presented in the form of mean peak ground acceleration (PGA) maps at 475 and 2500 year return periods and hazard curves for four seismically active areas in Sweden. We find the highest hazard in the northernmost part of the country, in the post-glacial fault province. This is in contrast to previous studies, which have not considered the high seismic activity on the post-glacial faults. We also find relatively high hazard along the northeast coast and in southwestern Sweden, whereas the southeast and the mountain region to the northwest have low hazard. For a 475 year return period we estimate the highest PGAs to be 0.04–0.05 g, in the far north, and for a 2500 year return period it is 0.1–0.15 g in the same area. Significant uncertainties remain to be addressed in regards to the SCR seismicity in Sweden, including the homogenization of small local magnitudes with large moment magnitudes, the occurrence of large events in areas with little prior seismicity and the uncertainties surrounding the potential for large earthquakes on the post-glacial faults in northern Fennoscandia.

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Reactivation of Non‐Optimally Orientated Faults Due to Glacially Induced Stresses

Steffen

2021

Tectonics

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The deformation due to an ice load is accompanied by displacement and stress changes. These stress changes are known to have created large‐magnitude earthquakes along pre‐existing faults during and after deglaciation of the Late Quaternary ice sheets. However, these so‐called glacially induced faults have been found to be not optimally orientated in their respective regional stress regime. Here, we analyzed the potential of non‐optimally orientated fault reactivation within a glacially induced stress field as well as changes of the stress regimes due to these additional stresses. A finite element model is used to estimate glacially induced stresses, which are then combined with background stress magnitudes. Non‐optimally orientated faults can be reactivated by glacially induced stresses within thrust‐, strike‐slip‐, and normal‐faulting stress regimes, but depending on their location with respect to the ice sheet and their orientation within the regional stress field. While faults with large variations of dip and strike outside of the ice sheet are prone to reactivation when the background stress field is a normal‐ or strike‐slip‐faulting stress regime, faults within a thrust‐faulting stress regime can also be reactivated within the ice margin during and after the deglaciation. Outside the ice margin, instabilities in a thrust‐faulting stress regime develop along the intermediate principal stress axis. Stress regime changes can occur for all background stress states. Finally, we find that certain conditions in a strike‐slip‐faulting stress regime can also explain the observed glacially induced thrust faults in Northern Europe.

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Postglacial Faulting in Norway

Cited by 6 publications

References 34 publications

The Concept of Lineaments in Geological Structural Analysis; Principles and Methods: A Review Based on Examples from Norway

The Concept of Lineaments in Geological Structural Analysis; Principles and Methods: A Review Based on Examples from Norway

Probabilistic Seismic Hazard Assessment of Sweden

Reactivation of Non‐Optimally Orientated Faults Due to Glacially Induced Stresses

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