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.

The most prominent fault scarps are found in northern Fennoscandia in the northernmost parts of Norway, Sweden and Finland. In addition, signs of glacially triggered faulting were identified in adjacent Russia. The following chapters give an overview about these faults from their identification until the very recent results that include, among other things, new reactivation dating and revised fault geometries at the surface from laser scanning.

The reactivation of glacially induced faults is linked to the increase and decrease of ice mass. But, whether faults are reactivated by glacially induced stresses depends to a large degree on the crustal stress field, fault properties and fluid pressures. The background (tectonic and lithostatic) stress field has a major effect on the potential for reactivation, as the varying stresses induced by the ice sheet affects the state of stress around the fault, bringing the fault to more stable or more unstable conditions. Here, we describe the effect of glacially induced stresses on fault reactivation under three potential background stress regimes of normal, strike-slip and thrust/reverse faulting. The Mohr diagram is used to illustrate how glacially induced stresses affect the location and the size of the Mohr circle. We review these different cases by applying an analysis of the stress state at different time points in the glacial cycle. In addition, we present an overview of fault properties that affect the reactivation of glacially induced faults, such as pore-fluid pressure and coefficient of friction.

The application of gravity gradient measurements to exploration has been growing over the past 20 years. The ability of tensor gradiometry instruments to greatly improve signal/noise when deployed on mobile platforms has transformed the usefulness of this technology. Airborne and marine Full Tensor Gradiometry (FTG) surveys have become an increasingly common part of the exploration and production toolkit. The ability of the modern instruments to provide high-resolution, spatial accuracy and very good signal/noise data has made this technology a more common part of integrated exploration and production management. The technology has a distinct cost advantage over seismic data acquisition and as such can deliver a competitive solution for imaging problems in some circumstances. There are now numerous published examples of effective use of FTG in the oil industry. The development of better instruments such as integration of direct contemporaneous measurement of conventional gravity is encouraging more interest in the technology. The potential for extending the use of FTG to reservoir monitoring and carbon dioxide sequestration assurance is likely to increase the popularity of the technology in future.

There is abundant evidence for high levels of seismic activity during deglaciation of Eastern Canada, suggesting that the seismic response of Eastern Canada to deglaciation is analogous to Fennoscandia, where numerous glacially induced faults have been confirmed. However, the Canadian record of glacially induced faults is scant. The two probable glacially induced faults that are described are few compared to the 100+ surface ruptures that are expected on statistical grounds. Alternative explanations to account for the small number of known ruptures are provided together with an interpretation of certain normal faulting that has been observed in glaciolacustrine sediments. It is recommended that the interpretation of prospective glacially induced fault features utilize a sceptical approach employing judgemental scales that reflect data limitations and associated uncertainties.

As glacially induced faults are reactivated due to a combination of tectonic and glacially induced isostatic stresses, it is interesting to model the corresponding fault slip with dedicated models. The next chapters introduce first such a modelling approach with a well-established model of glacial isostatic adjustment followed by a review of stresses to be considered in sophisticated future modelling.

The gravity and magnetic survey methods have been in use since the early days of geophysical prospecting for petroleum. They find most application in frontier exploration. In that context, regional and global datasets are often available to assist with early evaluations.

The design and execution of modern, targeted surveys has been transformed as a result of advances in instruments and the advent of satellite navigation. Imaging and interpretive techniques have been transformed by modern computer-based approaches. The potential field methods are extremely cost-effective at delineation of basins and determining structural controls on those basins, especially delineating normal faulting within rift basins. Magnetic surveys yield depth to basement and delineate any igneous rocks present. Such surveys therefore enable early decisions about cost-effective placement of seismic surveys and other intensive follow-ups.

In more mature exploration, gravity and gravity gradient data combine well with seismic data in distinguishing between alternate interpretations, thereby removing ambiguities. High-resolution magnetic data offer an effective means of fault connection in conjunction with regional seismic coverage, if shales or mudstones are present.

In a production environment, gravity logging is the most sensitive density log available, and 4D-gravity finds application in gas production and also water-flood monitoring.

Despite early studies indicating fault rupture both before and after deglaciation, it has long been hypothesized that glacially induced faults in Fennoscandia ruptured only once. The now widespread availability of high-resolution digital elevation models allows for testing this hypothesis by examining cross-cutting relationships between the scarps and both glacial and postglacial landforms. Although not widespread, such cross-cutting relationships indicate that segments of the Merasjärvi, Lainio and Pärvie faults have ruptured at least twice. The timing of the Merasjärvi ruptures is unknown; the Lainio ruptures occurred both before and after deglaciation, and at least one of the Pärvie ruptures is postglacial.

Additionally, it can be demonstrated that parallel segments of the Pärvie and Lansjärv faults ruptured at different times despite being only a few kilometres from each other. Given these results, the single rupture hypothesis must be reassessed for the high-relief scarps in northern Sweden, but it may still hold true for some of the low-relief scarps.

The chapter describes the exploration process which isfocussed on building a geological model of the subsurface which predicts the presence of hydrocarbons, and through a process of investment, reduces the uncertainty of the model so the risk of project failure is acceptable.

A staged approach for exploring for, and producing, oil and gas is described. First, explorers screen basins and find potentially prospective hydrocarbon provinces. Following this regional screening, they identify specific plays that may contain the elements for a working petroleum system (reservoir, source rocks and seal). Then, following a successful exploration programme that identified hydrocarbons, the next stage appraises the scale and productive characteristics of the discovery in order to design an effective, economic development. The traditional final stage is the production of the discovered hydrocarbons, where this is commercially attractive.In many basins the economic life of a reservoir is being extended to allow for the sequestration of carbon dioxide as a vital element in our ability to reduce carbon emissions.

The application of geophysical technologies to each stage of the exploration and production process is described through an articulation of the key problem that needs to be solved.The choice of which technology to use is determined by the geophysical property change and its scale.

Modelling of stresses that influence glacially triggered faulting has progressed substantially in the last decades with more complex models and improved modelling techniques, incorporation of a variety of relevant processes, better constraints of ice-loading history, higher model resolution and 3D geometries. Some recent developments are collected in this section to portray the scope and variability of numerical modelling relevant to glacially triggered faulting. These range from modelling of the general in situ stress field to studies on the stress field induced by glacial loading and unloading.

An appropriate estimation of the ambient background stress field is crucial for determining the effect of additional ice loading (or unloading) on pre-stressed faults. Contributions from local and far-field stress sources (topography, tectonics) need to be reconciled with in situ measurements from boreholes and fault-plane solutions from earthquakes. We describe the different types of stresses in glaciated regions with a focus on Scandinavia together with the techniques used to incorporate stresses into numerical models.

To model glacial triggering of earthquakes, it is necessary to obtain the spatio-temporal variation of glacial isostatic adjustment-induced stress during a glacial cycled. This can be computed efficiently using commercial Finite Element codes with appropriate modifications to include the important effects of ‘pre-stress advection’, ‘internal buoyancy’ and ‘self-gravity’. The modifications described in Wu (2004) are reviewed for incompressible and so-called materially compressible flat-earths. When the glacial isostatic adjustment-induced stress is superimposed on the background tectonic stress and overburden pressure, the time variation of earthquake potential at various locations in the Earth can be evaluated for any fault orientation. To model more complex slip and fault behavior over time, the three-stage Finite Element model approach of Steffen et al. (2014) is reviewed. Finally, selected numerical examples and their results from both modelling approaches are shown.

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.

Microseismic monitoring, an extension of classical earthquake seismology, has found many applications in the resource industry. In particular, it has become an essential tool for observing the results of hydraulic fracturing on unconventional reservoirs, without which the reservoirs are not economic. Such monitoring allows for direct observation of the effectiveness of the well treatment, for the selection of improved treatment parameters, and contributes to the overall field development plan. Data from microseismic monitoring contributes to the understanding of the stimulated reservoir model, the drainage volume of individual wells, estimated production, production interference and the stress in the reservoir. This chapter presents an introduction to how these data are acquired, analysed and integrated with other data to affect a successful well completion and field development program.

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.

The polar region is the area surrounding the Earth’s geographical poles (Antarctica, Arctic). While glacially induced faults are well known in the formerly glaciated areas of Northern Europe, such faults within the Arctic and Antarctica are unidentified, although the theory of their physical mechanism would allow their presence. Mainly, the fact that most of the polar region is covered either by ocean (Arctic) or ice sheets (Antarctica, Greenland) prevents detailed analysis of those regions with respect to glacially induced faults. However, there are several indications that suggest an existence of glacially induced faults in the polar region. Here, we summarize findings about potential glacially induced faults in Northern Canada, Greenland, Iceland and Svalbard on the northern hemisphere and revisit the seismicity in Antarctica.