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Paleoseismicity of Sweden - a novel paradigm

  • January 2003
  • Edition: 2003
  • Publisher: Paleogeophysics & Geodynamics (P&G)
  • Editor: Nils-Axel Mörner
  • ISBN: ISBN-91-613.4072-1
Authors:
Nils-Axel Mörner at Paleogeophysics and Geodynamics Institute
Nils-Axel Mörner
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At the time of deglaciation, Sweden, like the rest of Fennoscandia, was an area of high to super-high seismic activity. This novel paradigm is here presented in a series of fifteen papers.
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Paleoseismicity of Sweden
a novel paradigm
Nils-Axel Mörner
Paleogeophysics & Geodynamics, Stockholm University, Stockholm, Sweden
At the time of deglaciation,
Sweden,
like the rest of Fennoscandia,
was an area of high to super-high seismic activity.
This novel paradigm
is here presented in a series of fifteen papers.
This book is a contribution
to the INQUA XVI Congress in Reno, Nevada, in 2003
by the Editor and Authors
and the Sub-Commission on Paleoseismology
of the INQUA Commission on Neotectonics
previously from the author (besides numerous research papers):
Earth Rheology, Isostasy and Eustasy
Editor: Nils-Axel Mörner
John Wiley & Sons, 1980
Climatic Changes on a Yearly to Millennial Basis
Editors: N.-A. Mörner & W. Karlén
Reidel, 1984
Bulletin of the INQUA Neotectonics Commission, Nos. 1–19
Editor: Nils-Axel Mörner
INQUA, 1978–1996
Printed in 2003
by
JOFO Grafiska AB
for
Nils-Axel Mörner
Paleogeophysics & Geodynamics
ISBN–91–631-4072-1
© Nils-Axel Mörner
Produced and distributed
by
Nils-Axel Mörner
Paleogeophysics & Geodynamics, Stockholm University, S-10691 Stockholm, Sweden
www.pog.su.se, Tel. 46-8-164671, Fax. 46–8-164675, E-mail: morner @ pog.su.se
CONTENTS
Paper Title Page
1 Paleoseismicity of Sweden. A novel paradigm 5
2 The Fennoscandian uplift; mode, amount and rates 9
3 Ground shaking and paleoseismic marker-beds 19
4 The Umeå region: the Röbäck structures and events 21
5 The Hudiksvall region: the Boda Cave and its surroundings 29
6 The North Uppland region: Gillberga Gryt and Mehedeby 225
7 The Mälardalen region: the autumn 10,430 BP event 229
8 Southeast Sweden 265
9 The Kattegatt – West Coast area 269
10 The “spotted zone” in the new light of paleoseismics
and methane venting 289
11 The new Active Tectonics map of Fennoscandia 295
12 Paleoseismic Catalogue of Sweden, 2003 301
13 Causal correlation between rate of uplift and paleoseismicity 309
14 Paleoseismics and General Quaternary Geology of Sweden
New aspects in the light of the novel concept of
a high deglacial seismicity 313
15 General Conclusions 319
The 15 papers included are not numbered but marked by their main heading in red.
Mörner: Paper 476-A
Paleoseismicity of
Sweden a novel paradigm
Nils-Axel Mörner
Paleogeophysics & Geodynamics, Stockholm University, Stockholm,
Sweden
Chapter 1
Paleoseismicity of Sweden
A novel paradigm
5
Paleoseismicity of Sweden
A novel paradigm
Nils-Axel Mörner
Paleogeophysics & Geodynamics, Stockholm University, Stockholm, Sweden
Sweden, like the rest of Fennoscandia, has generally been considered to be a stable craton
with low to moderately low seismic activity. Whilst this may be true for today and preglacial
times, it is totally wrong for the deglacial phase with peak rates of glacial isostatic uplift
(Mörner, 1991). The seismic mode – in intensity as well as in driving forces – was simply not
the same as today. At the time of deglaciation, Sweden was a high-seismic region; in seismic
magnitudes as well as in seismic frequency. This has wide implications and we may hence
talk about a novel paradigm.
Geo-philosophy
The problem of continuity or discontinuity is vital in geology. We debate the present as a key
to the past and the past as a key to the present and future. The alternations between ice ages
and interglacials give firm evidence of drastic changes between two climatic modes. In
seismicity, however, we have no previous documentation of any significant changes in mode.
The Swedish data record a drastic change between a high to super-high seismic mode at the
time of deglaciation and a low to moderately low seismic mode today (Papers 5, 7, 13). This
has wide implications in paleoseismics and geodynamics.
Structural criteria
A fault may be easily identified in an open area. Fault covered by sediments and faults in deep
forests are very hard, sometimes even impossible, to trace by simple ground observations.
Therefore, we have to rely on secondary structures like bedrock fracturing, sediment
deformation, liquefaction, tsunami beds, slumps and other effects of ground-shaking. Our
studies of various forms of liquefaction and their relation to varves are of basic significance in
the study of paleoseismics in Sweden (Papers 5, 7, 9). The varve-dating often allows us to
assign an age of the paleoseismic event as to one single year. Because of this unique time
resolution, we are also able to define the spatial distribution of liquefaction which provides an
independent relative measure of seismic magnitudes (Paper 5, Fig. 5; Mörner, 2001).
Practical implication
Because of the drastic change in seismic mode between today and the time of deglaciation,
any statistical treatment of present day data will have no significance what so ever for long-
term safety and hazard estimates (Paper 5, section 12). The whole concept of a long-term
stability and hence a “safe” storage for an unguarded high-level nuclear waste repository falls
apart as fiction and expectation rather than sound geological facts (e.g. Mörner, 2001).
Geological implications
The concept of a high deglacial paleoseismicity including extensive ground-shaking (with
related deformation of sediments and bedrock surfaces), wide areas of liquefaction and
multiple tsunami events has fairly large implication in our understanding and interpretation of
Swedish Quaternary geology (Paper 14). So, for example, is the onset of the classical Yoldia
Sea stage (sensu stricto) in the Baltic now understood in terms of an exceptionally large
6
earthquake occurring in the autumn of varve 10,430 vBP which gave rise to a tsunami wave
that washed the Närke Strait free of pack-ice and ice-bergs allowing the Atlantic water to
invade the Baltic momentarily (Mörner, 1995, 1996). In several cases and especially in the
county of Halland, different sedimentary deformations were misinterpreted in terms of glacial
tectonics and frost activity with lead to quite absurd ideas regarding glacial conditions and sea
level changes (further discussed in Paper 9).
INQUA Neotectonics Commission
As secretary and president, I was for many years (1978-1994) responsible for the INQUA
Commission on Neotectonics. During this period, the commission transformed into a both
important and effective international body. In collaboration with a large number of
colleagues, we step by step built up a deep understanding of neotectonics and paleoseismics
as recorded in the annual Bulletin of the Neotectonics Commission (19 issues). From 1981,
we had a separate sub-commission on paleoseismics. No doubt, the INQUA Neotectonics
commission is the base also for our progress in Sweden.
Paleogeophysics & Geodynamics
Having been employed by the Swedish National Research Council since 1973 and organised
the international GDP-meeting in Stockholm in 1977 on “Earth Rheology and Late Cenozoic
Isostatic Movements” (Mörner, 1980), I, in 1991, got a separate unit at Stockholm University
on Paleogeophysics & Geodynamics. This initiated intensive work on paleoseismics and
neotectonics including Ph.D. projects (e.g. Sjöberg, 1994; Tröften 1997). After an intensive
debate, we were, in 1997, granted funding for the “Boda Cave Project” allowing us to work in
an effective international team and being able to present a heavy report built on integrated
studies using multiple parameters (Paper 5; Mörner et al., 2001). In 1999, we run a major
international excursion through Sweden visiting most sites of paleoseismic findings and a
number of key sites in the study of land uplift and sea level changes (Mörner, 1999).
Personal aspects
Our Boda Cave Report (Mörner et al., 2001; Paper 5) was finished and presented to SKB on
the Swedish National Day, June 6, 2001. We had an extensive observational material from the
whole of Sweden from Umeå in the north to Skåne in the south. Also, I had together with
Franck Audemard cleaned up and documented all available sites of liquefaction structures.
Therefore, I decided to compile all data in a separate book. This book on “Paleoseismicity of
Sweden” is a contribution to the INQUA XVI Congress in Reno in 2003 from the Sub-
commission on Paleoseismology of the INQUA Commission on Neotectonics.
Integration and interaction
Fig. 1 illustrates the integration of isostasy and eustasy in the observed changes in sea level in
Fennoscandia further discussed in Paper 2. It also, illustrated its potential in testing different
eustatic factors and the rheological parameter behind uplift. As output also comes a new
concept of neotectonics, which includes the presently presented new paradigm on seismo-
tectonics and paleoseismics with a high to super-high activity some 9000–11,000 years ago.
Fig. 2 illustrates the global geophysical system of multiple interacting parameters in
response to an Ice Age with formation of continental ice caps. The system includes many
different variables and effects operating in feedback coupling relation.
7
Fig. 1. Separation of isostasy and eustasy and their effects on different concepts.
Fig. 2. Global interaction of multiple parameters and their feedback coupling.
8
References
Mörner, N.-A., 1980. Earth Rheology, Isostasy and Eustasy (N.-A. Mörner, Ed.), John Wiley,
p. 1-599.
Mörner, N.-A., 1991. Intense earthquakes and seismotectonics as a function of glacial
isostasy. Tectonophysics, 188, 407-410.
Mörner, N.-A., 1995. The Baltic Ice Lake–Yoldia Sea transition. Quaternary International,
27, 95-98.
Mörner, N.-A., 1996. Liquefaction and varve disturbance as eveidence pf paleoseismic events
and tsunamis; the autumn 10,430 BP event in Sweden. Quaternary Sci. Rev., 15, 939-
948.
Mörner, N.-A., 1999. Sweden Excursion, May 1999. Sea level changes, uplift, paleo-
seismicity, climate, coastal dynamics. Excursion guide, P&G, Stockh. Univ., 81 pp.
Mörner, N.-A., 2001. In absurdum: long-term predictions and nuclear waste handling.
Engineering Geology, 61, 75-82.
Mörner, N.-A., Audemard, F., ., Bronge, C., Dawson, S., Grant, D., Kvamsdal, O., Nikonov,
A., Sidén, A., Sjöberg, R., Strandh, L., Sun, G., Tröften, P.E., Wigren, H. and Zykov, D.,
2001. The Boda Cave and its surroundings. The 9663 BP paleoseismic event. Report to
SKB, www.pog.su.se (public).
Sjöberg; R., 1994. Bedrock caves and fractured rock surfaces in Sweden. Occurrence and
origin. Ph.D.-thesis, P&G, Stockholms Universitet, 110 pp.
Tröften, P.E., 1997. Neotectonics and paleoseismicity in southern Sweden with emphasis on
sedimentological criteria. Ph.D.-thesis, P&G, Stockholms Universitet, 124 pp.
Note about the dating systems used in this book
In this book, I discuss dates derived from both varves and radiocarbon.
For distinction, I label varve-ages with vBP and C14-ages with cBP.
... Wikström, 2015). Gotland lay beneath a large icestream flowing south during glacial maxima, and thus experienced significant glacial erosion and then large earthquakes during isostatic rebound (Mörner, 2003). Following deglaciation in the Bølling-Allerød (B-A) Interstadials, the island was flooded by the Baltic Ice Lake, the brackish Yoldia Sea, and the freshwater Ancylus Lake, for several millennia (Fredén, 2009). ...
... There are >2000 tectonic fracture and talus caves formed in non-karstic rocks in Sweden and many in Norway, where Ljøtehølet in southern Norway has a depth of 55m (Schrøder, 1980). The longest talus cave is Bodagrottorna in Sweden, which comprises a field of large talus blocks ( Figure 6) above entrances that reach a depth of 11m (Mörner, 2003). The total length of its underground cavities is 2600m. ...
... Because eustatic sea level was also rising as the planet deglaciated, the absolute uplift since the start of the B-A relative to the centre of the Earth was much higher. It has reached c. 830m at the centre of the pre-B-A Scandinavian ice dome, which was c. 100km west of the Baltic coast in Sweden (Mörner, 2003). ...
The ages of the Scandinavian caves. [Published in Norsk Grotteblad (70), 15-33, 40]
Article
Full-text available
  • Jun 2018
Over 2550 dissolutional caves are known in Norway and Sweden. These caves have formed mainly in stripe karst Caledonide marble outcrops that have negligible primary porosity. Speleogenesis was commonly initiated by tectonic inception, in fractures caused by isostatic rebound during one or more Quaternary deglaciations. This was followed by dissolution in fast-flowing aggressive meltwater during deglacial speleogenesis in phreatic conditions and sporadically by later interglacial speleogenesis, creating tiers of relict phreatic passages above an active streamway in the more complex caves. About 50 dissolutional caves are also formed in other limestones. Well over 300 coastal caves are recorded along the coastlines, with about 50 tunnel caves above the Baltic coast, and over 800 fracture and over 1200 talus caves occur in both countries. This article reaches the firm conclusion that the survival of any non-hypogenic karst cave passages formed before the Mid-Pleistocene Revolution, about one million years ago, would be exceptional. The larger Norwegian coastal caves were mainly formed and enlarged by marine abrasion and ice wedging during the onsets of one or more of the last few glaciations and by later roof collapses. Some probably exist beneath the Norwegian Sea. The same processes enlarged the entrances of several well-known karst caves. The fracture and talus caves were formed by seismic events during Weichselian deglaciation. Because of the removal of caves and cave passages by the glacial erosion of marbles and other rocks, many surviving caves might be related to earlier palaeo ‘cave passages in the sky’.
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... The ideas were proposed in early papers by Mörner (1979) and Sjöberg (1986). They were later expanded in comprehensive works by Mörner et al. (2000), Mörner (2003) and Mörner and Sjöberg (2018), which included the theory that some earthquakes were accompanied by explosions of methane gas, as reported most recently by Mörner et al. (2021). In parallel with this research, the Swedish cave database recorded the existence of >2000 non-karst caves, some being described in Grottan. ...
... Text & foto: Trevor Faulkner the formation of talus caves, fracture caves and the deformations of sedimentary deposits along the coast, which have been well-dated to seismic events in the early Holocene (Mörner, 2003). Although this theory might need to be expanded at some sites to include modern ideas about paraglacial Rock Slope Failures after deglaciation, it is just dismissed by the authors in favour of their new proposal, without any comparative discussion of it or its merits. ...
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... Ice c. 3 km thick melted away at the end of the Weichselian glaciation. This caused rapid isostatic rebound that peaked at c. 0.5 m per year at the Baltic coast during the early Holocene (MÖRNER, 2003) and produced steep sea level curves at the Norwegian coast (SVENDSEN & MANGERUD, 1987). The rapid uplift created large earthquakes up to Magnitude 8, as evidenced by many examples of screes, rock splitting, soft sediment deformation (Fig. 3), mega-slides, talus (Fig. 4) and talus caves on the Swedish High Coast (MÖRNER & SJÖBERG, 2018). ...
The high-flow low-storage extreme in marble aquifers. [Published in the Proceedings of the 18th International Congress of Speleology, France, 2022, Vol 4, 129-132.]
Conference Paper
Full-text available
  • Jul 2022
High grade marbles have negligible primary porosities after limestone metamorphism. Nevertheless, there are >2800 marble caves in Scandinavia, Scotland and North America. About a third consist of shallow vadose passages without pre-Holocene speleothems, which could not have survived the last glaciation. They therefore formed during the Holocene. However, other caves in Norway clearly pre-date the Holocene or survived several glaciations. These were initiated by phreatic 'pure' water flows from ice-dammed lakes through neotectonic fractures that were opened by isostatic rebound during deglaciation, many passages being horizontal even in vertical and angled foliations. Some flow routes were short enough and fractures wide enough for fast flow rates (shown by small sizes of later wall scallops) during tectonic inception to be immediately beyond rates required for chemical breakthrough or even for the Fast Rate Law. This was despite the absence of vegetation, resulting in little CO 2 in pure glacial meltwater. Phreatic passages enlarged at fast rates to ≤2 m diameter in the typical 1000 years duration of deglacial water flow, possibly followed by vadose entrenchment in the succeeding interglacial. The resulting marble aquifers have high flow rates and low storage capacity.
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... На протяжении последних десятилетий в региональной геологии выдвинут ряд принципиально важных положений, позволяющих по новому подойти к проблеме тектонической активности и сейсмичности платформенных (щитовых) территорий. Трудами разных исследователей, как в России, так и за рубежом собрано множество свидетельств о следах сильных древних землетрясений в Фенноскандии (Lukashov, 1995, Николаева, 2001, 2013, Morner, 2003, Kukkonen et al., 2010, Родкин и др., 2012, и др.). При этом сама проблема позднеледниковой и голоценовой сейсмичности остается дискуссионной как по вопросам генезиса, так и параметризации палеоземлетрясений. ...
Шонгуйские дислокации в структуре основных сейсмогенных зон Кольского региона: проявления, тектоническая позиция, возраст
Article
  • Jan 2020
Abstract. The paper presents new results of seismogeological studies in the northern Kola Region. Various types of seismic dislocations near the Shonguy settlement have been thoroughly studied, which allows to specify parameters of possible seismic sources specify the structural position of the focus and collect information on the kinematics of seismogenic blocks. It has been found that the Shongui dislocations are associated with a large morphostructural zone of higher order where strong earthquakes occurred repeatedly at the end of the Late Glacial and during the Holocene. Key words: paleoseismic dislocations, earthquakes, seismogenic zone, Kola Peninsula, Fennoscandian Shield.
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... Numerous traces of strong earthquakes were discovered and studied in the recent decades in the different parts of Fennoscandia, from the west -in Sweden, Norway, and Finland (Kujansuu, 1964;Lundqvist & Lagerbäck, 1976;Olesen et al., 1992;Sjöberg, 1994;Bungum & Lindholm, 1997;Kuivamäki et al., 1998;Dehls et al., 2000;Mörner, 2003;Lagerbäck & Sundh, 2008;Kukkonen et al., 2011), to the east -in Russia (Lukashov, 1995(Lukashov, , 2004Zykov, 2001;Nikonov et al., 2001;Nikonov, , 2003Nikonov, , 2007Nikonov, , 2008Nikonov & Miidel, 2003;Nikolaeva, 2008;Nikolaeva et al., 2016;Nikonov & Zykov, 2017). ...
New evidence of the Vuoksi River origin by geodynamic cataclysm
Article
Full-text available
  • Dec 2018
The territory of investigations is located in the SE periphery of the Fennoscandian Shield. It served as an arena of periodic significant restructuring of the hydrographic network associated with the filling and discharge of large late-glacial and Holocene basins during the degradation of the Scandinavian ice sheet and in postglacial time. One such restructuring is a sudden change of the Saimaa Lake direction of flow in the middle Holocene from the west to south to the Lake Ladoga basin via the drainage hollow, inherited by modern Vuoksi River valley. Origin of the Vuoksi River is associated with the catastrophic water breakthrough of the Saimaa Lake across the marginal ridge Salpausselkä I of about 5.7 cal. kyr BP. This event usually connects with water accumulation and overflow due to non-uniform post-glacial uplift according to modern concepts. The authors propose a great earthquake as the immediate cause of the break waters of Saimaa Lake. This suggestion is based on the study of specific deformations of the rocky riverbed in the area of breakthrough and of the loose deposits in the banks of the Vuoksi River valley downstream. Open cracks and horizontally displaced rock blocks were discovered in the area of the former rapids near town Imatra. Their systematic displacements on the both sides of the rocky gorge indicate the shear kinematics of fault zone. Different types of deformations had occurred in loose sediments of the low terraces (3–4 m) in the Vuoksi River valley and 20–30 km below the headwaters. In three studied stratigraphic sections the three cardinal different types of deformations were discovered: 1) normal fault with vertical displacements, 2) tectonic inclination, and 3) traces of catastrophic mudflow. The time diapason of the terrace forming (and of the corresponding deformations) is determined of 8.3 to 1.8 cal. kyr BP (by the ages of adjacent terrace levels), which corresponds to the origination time of the Vuoksi River. The earthquake, which presumably was a trigger for the formation of the Vuoksi River, was generated by the activation of ancient fault zone, manifested in the crystalline foundation. Periodic post-glacial tectonic activity of this zone is revealed in traces of strong seismic events both in the bedrock (initial emergence of the gorge, its renewal during the breakthrough), and in loose deposits (deformations in different levels of terraces).
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... The late-and post-glacial fragmentation of rocks and the deformation of glacial, lacustrine and alluvial sediments was presumably the cause of large earthquakes as described by researchers for different localities in the western part of the Fennoscandian crystalline shield (Kujansuu, 1964;Lundqvist & Lagerbäck, 1976;Bungum & Lindholm, 1997;Kuivamäki et al., 1998;Mörner, 1985Mörner, , 2003Mörner et al., 2003;Olesen et al., 1992;Sjöberg, 1994;Lagerbäck & Sundh, 2008;Kukkonen et al., 2011). Similar studies were carried out for the eastern Fennoscandia, which consists of Russian Karelia, the Kola Peninsula, and the Karelian Isthmus (Lukashov, 1995(Lukashov, , 2004Nikonov & Zykov, 1996;Zykov, 2001;Nikolaeva, 2006;Nikonov, 2008;2012;Nikonov et al., 2014;Nikonov & Shvarev, 2015;Nikolaeva et al., 2017;Shvarev & Rodkin, 2018). ...
The active tectonics of the Vuoksi Fault Zone in the Karelian Isthmus: parameters of paleoearthquakes estimated from bedrock and softsediment deformation features
Article
Full-text available
  • Dec 2018
The area under study is located in the south-eastern periphery of the Fennoscandian crystalline shield. At present this is a tectonically quiet region without large seismic events. But it is well known that in post-glacial time the Fennoscandian shield was an arena of active postglacial tectonics and large earthquakes. The evidence for such events was found in various parts of Fennoscandia. The traces left by some paleoearthquakes show an undisputed character of large post-glacial faults some tens of kilometres long and of a few meters in displacement. However, some other features left by earthquakes are under discussion. Numerous deformations in bedrock and in soft sediments which can be considered as being due to earthquakes were found in the Russian Karelia. Interpretation of some of these deformation structures can lead to different conclusions about their origin, for example, weathering, cryogenic, glacial, and gravitational factors. One possible way to overcome these difficulties is an integrated study of different types of deformations at key sites, comparison of these with each other and with the tectonic features of the region, and the search for common structural and kinematic features. Another problem is the estimation of parameters of paleoearthquakes. This problem includes the determinations of their location, intensities, magnitudes, and age. The key site under study is located in the northern part of the Karelian Isthmus in the re-activated (during post-glacial time) tectonic zone (the Vuoksi Fault Zone), whose signature in the relief is seen in the form of the straight-line valley of the Vuoksi River. We studied different types of post-glacial seismogenic deformations at this locality. There are seismically induced gravitational and vibrational deformations in solid rock, as well as folds and ruptures in loose sediments. The key site of large deformation examined here includes three zones: 1) the main zone of deformations or the Central Fractured Massif (CFM); 2) the seismically induced colluvial zone; 3) the outer zone of deformations in loose sediments. We have established that all types of deformations are kinematically similar in the CFM and around it (at distances of a few kilometres). A detailed examination of deformations and their spatial and temporal relationships allows us to distinguish three generations of earthquake-induced deformations: 1) Late Glacial, 2) Early Holocene, and 3) Middle to Late Holocene. We estimate the intensities of the respective earthquakes as I=IX, IX, and VII-VIII. Clearly, the intensities decrease from post-glacial to present time, but the recent level of seismicity is unclear and may be much higher than hypothesized. In addition, the evidence for shear kinematics of the fault shows that earthquakes were not only caused by post-glacial rebound, but also resulted from a different tectonic mechanism possibly related to plate tectonics.
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Part III - Glacially Triggered Faulting in the Fennoscandian Shield
Article
  • Dec 2021
Glacially triggered faulting describes movement of pre-existing faults caused by a combination of tectonic and glacially induced isostatic stresses. The most impressive fault-scarps are found in northern Europe, assumed to be reactivated at the end of the deglaciation. This view has been challenged as new faults have been discovered globally with advanced techniques such as LiDAR, and fault activity dating has shown several phases of reactivation thousands of years after deglaciation ended. This book summarizes the current state-of-the-art research in glacially triggered faulting, discussing the theoretical aspects that explain the presence of glacially induced structures and reviews the geological, geophysical, geodetic and geomorphological investigation methods. Written by a team of international experts, it provides the first global overview of confirmed and proposed glacially induced faults, and provides an outline for modelling these stresses and features. It is a go-to reference for geoscientists and engineers interested in ice sheet-solid Earth interaction.
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Seismicity and Sources of Stress in Fennoscandia
Chapter
Full-text available
  • Dec 2021
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.
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geosciences History of the Environmental Seismic Intensity Scale ESI-07
Article
Full-text available
  • May 2019
This brief note aims to describe the history, from its early original idea, of the new macroseismic scale: The Environmental Seismic Intensity Scale 2007 (ESI 2007). It can be used together with other existing scales or alone when needed for measuring the intensity of an earthquake on the basis of the primary and secondary effects of a seismic event on the natural environment. These effects could be the major sources of earthquake hazards, as recently proved. This note also aims to contribute to the understanding of processes that induced the researcher to develop an idea, to pursue it, and bring it to its end, first through the help of valuable Italian researchers and then through the constructive exchange of ideas with researchers of different cultural backgrounds operating almost everywhere in the world. This note is sponsored and approved by the International Union for Quaternary Research (INQUA), and the Environmental Seismic Intensity scale (ESI-07) was published in 2007 after a revision process of about eight years.
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Jordbruelv revisited [Published by the Norwegian Speleological Society in Norsk Grotteblad (56) 16-30, 32, 2011]
Article
Full-text available
  • Jan 2011
Norsk Grotteblad nr 56, Juni 2011 Jordbruelv revisited The Jordbruelv, a large tributary of the Gåsvasselv, drains the western sides of Elgfjell and Jordhulefjell in Grane kommune, south Nordland, within the Lomsdal – Visten National Park. It has a catchment area of c. 30km2, providing an annually-averaged flow rate of ~2m3sec-1. Faulkner (2009a) described the Elgfjell / Jordbruelv area and its geology. The major marble outcrop in the lower Jordbruelv area is mapped as a single outcrop ~600m wide at Bjørkåsen and Fatfjell. This continues north via Gåsvatn to Elgfjell as separate ‘fingers’ that dip at 60–70°W. However, the caves reported here lie within a narrower band of Vertical Stripe Karst (VSK) that is separated by c. 500m of mica schist from the main outcrop to its east. It follows the Jordbruelv valley north via the Jordbru (Rockbridge) to the head of the Jordbruelv Gorge, where the stream meets the limestone at the Waterfall, and continues along the ridge towards the summit of Jordhulefjell. This marble outcrop comprises grey, or grey and white striped, Low Magnesium Calcite: the yellow-brown striped variety of High Magnesium Calcite, seen on Elgfjell, has not been observed in the lower Jordbruelv area. The caves near the powerful Jordbruelv Waterfall and downstream via the Jordbruelv Gorge to beyond the Jordbru are summarised, together with their exploration. These include Etasjegrotta, the Invasjonsgrotta – Cliff Cave system and the Vatnhullet – Jordbru Main Rising submerged system. It is now clear that these caves comprise parts of one hydrologically-connected system that has a total length over 3km. The speleogenesis of this system is considered: (a) from the evidence of deglacial neotectonic movements seen on the surface in the Gorge and the Jordbru and underground in Beehive Cave, Cliff Cave and Invasjonsgrotta; (b) from the likely deglacial hydrology at the end of the Weichselian glaciation (Faulkner, 2005); and (c) from the nature of the laminated sediment bank in Oddstue in Invasjonsgrotta that records seismic liquefaction whilst still submerged just below the surface of the Elgfjell icedammed lake. By working backwards in time and upwards in elevation, a scenario for the development stages for the system is presented. It is concluded that the Jordbruelv Gorge and the Jordbru have probably existed for two or three glacial cycles, when the Jordbruelv valley started to create the deeper hydraulic gradients necessary for local interglacial cave development during and after the ‘Super Saalian’ glaciations. The relict Cliff Cave – Invasjonsgrotta phreatic conduit probably enlarged to its present size when submerged during the final Saalian deglaciation that ended about 128,000 years ago, when the water resurged from an entrance north of Vatnhullet. The submerged Whybro Passage beneath it likely started to carry water that emerged as a Vauclusian rising at Vatnhullet at the same time and during the following Eemian interglacial. It then continued to enlarge to its 10m diameter during the Weichselian deglaciation and the Holocene, when the Vatnhullet entrance was bypassed by fractures leading to the Main Rising, after the Gorge and Jordbru had been excavated nearly to the present depth. Etasjegrotta is probably a more-recent development that started synchronous phreatic enlargement of its tiered conduits on about 20 levels during the Weichselian deglaciation (although its inception fractures and the upper phreatic loops may date from the Saalian deglaciation) and has continued with vadose entrenchment and phreatic enlargement at its lowest levels only during the Holocene.
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Bedrock caves and fractured rock surfaces in Sweden : occurence and origin
Article
Full-text available
  • Nov 2013
Thèse (doctorat)--Stockholm University, 1994. Earlier it has been stated that seismotectonically formed features only occured in the northern parts of Sweden. The aim of this thesis has been to analyse the distribution and probable origin of a large number of fractured bedrock surfaces, fractured hills, boulder heaps as ”blown up” hills (several of these containing long cave systems), and some large rock slides containing cave systems. These features are found all over Sweden. For the first time these phenomena have been described in one context. The origin of these features has been looked for among the following processes: glacial tectonics, frost deformation, postglacial aseismic stress adjustment, hydro-fracturing, methane ventings and seismotectonics. During the deglaciation of the Weichselian ice-sheet a combination of a very fast isostatic uplift, and corresponding changes in stress and strain, resulted in a (especially in northern Sweden) well documented neoseismotectonic activity. Several bedrock features such as a number of fractured surfaces, fractured hills, boulder heaps (with and without cave systems), and some collapsed rock walls (often containing caves), seems to have been formed as a function of this neoseismicity. In certain cases a possible combination with other processes such as methane wentings, hydro-fracturing, and post glacial stress adjustment cannot be excluded. The neoseismotectonic bedrock features described in this thesis are distributed over most parts of Sweden: - or rather wherever we have looked for them
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In absurdum: Long-term predictions and nuclear waste handling
Article
Careful use of scientific knowledge allows predictions into the future. When the time units for our predictions increases to hundreds of thousands of years, we have extended our abilities 'in absurdum'. This is true for long-term safety statements regarding the handling of our high-level nuclear waste. The Fennoscandian Shield has been claimed to offer exceptionally stable bedrock conditions over immense time periods. We only need to go back to the last deglacial phase some 10,000 years ago to have a totally different situation from that of today. At that time Sweden was characterized by exceptionally high seismic activity; both in amplitude and frequency. These conditions (like a number of related phenomena) will be repeated at future Ice Ages. In such an environment, there can be no safe repository in the bedrock. In the absence of true long-term safety, we can only recommend the utilization of the Dry Rock Deposit (DRD) method where the waste is stored in the bedrock under dry conditions, under constant control and monitoring, accessible for maintenance and possible future methods of rendering the waste harmless and even removal.
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The Baltic Ice Lake-Yoldia Sea transition
Article
The Baltic Ice Lake, the Yoldia Sea, the Ancylus Lake and the Littorina Sea are the four classical stages in the postglacial evolution of the Baltic basin. The picture is complicated by what concerns the details of each of these stages. Between the Baltic Ice Lake and the Yoldia Sea it is necessary to introduce a separate lake stage; an entirely lacustrine phase of 300 years right after the drainage of the Baltic Ice Lake and before the ingression of salt water that, by definition, signifies the onset of the Yoldia Sea. During this lake stage, a fully lacustrine ‘Ancylusfauna’ lived along the coasts of the islands of Gotland and Öland. For historical reasons and mistakes, we term this new stage the ‘Yoldia’ Lake stage (thus avoiding too much reorganization).
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Liquefaction and varve deformation as evidence of paleoseismic events and tsunamis. The autumn 10,430 BP case in Sweden
Article
Coastal seismic events generate instantaneous changes in relative sea level (i.e. land level vs sea level). Tsunamis may cause disastrous damage to coasts and coastal habitation. Liquefaction and deformations of annually varved sediments provide information on paleoseismic events. The evidence for a major earthquake and associated tsunami waves in Sweden are explored. Thanks to the varve chronology, liquefaction structures and varve deformations caused by this event can be dated at the autumn 10,430 varve years BP. The magnitude is estimated at 8 (or more) on the Richter scale. The tsunami washed the previously blocked outlet of the Baltic free of icebergs and pack-ice so that marine water could suddenly invade the entire Baltic, forming the Yoldia Sea.
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Intense earthquakes and seismotectonics as a function of glacial isostasy
Article
Old shields and plate interiors have often been assumed to exhibit a high crustal stability. During the last decade, or two, we have learnt more and more about the fragility, not to say untenability, of this concept, however. High-magnitude earthquakes and large scale fault-movements have been recorded where they were not supposed to be able to occur. Within formerly glaciated areas like Northern Europe, Scotland and northern North America a rapidly increasing number of field observations indicates that the glacial isostatic readjustment process was linked to intense seismotectonic activity. We will here investigate the Fennoscandian situation and propose a novel causation model for the high deglaciation seismicity in comparison with the present day situation.
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Sea level changes, uplift, paleoseismicity, climate, coastal dynamics. Excursion guide
  • May 1999
  • pp
  • N.-A Mörner
Mörner, N.-A., 1999. Sweden Excursion, May 1999. Sea level changes, uplift, paleoseismicity, climate, coastal dynamics. Excursion guide, P&G, Stockh. Univ., 81 pp.
The Boda Cave and its surroundings. The 9663 BP paleoseismic event
  • Jan 2001
  • N.-A Mörner
  • F Audemard
  • C Bronge
  • S Dawson
  • D Grant
  • O Kvamsdal
  • A Nikonov
  • A Sidén
  • R Sjöberg
  • L Strandh
  • G Sun
  • P E Tröften
  • H Wigren
  • D Zykov
Mörner, N.-A., Audemard, F.,., Bronge, C., Dawson, S., Grant, D., Kvamsdal, O., Nikonov, A., Sidén, A., Sjöberg, R., Strandh, L., Sun, G., Tröften, P.E., Wigren, H. and Zykov, D., 2001. The Boda Cave and its surroundings. The 9663 BP paleoseismic event. Report to SKB, www.pog.su.se (public).
Note about the dating systems used in this book In this book, I discuss dates derived from both varves and radiocarbon. For distinction, I label varve-ages with vBP and C14-ages with cBP
  • Jan 1997
  • P E Tröften
Tröften, P.E., 1997. Neotectonics and paleoseismicity in southern Sweden with emphasis on sedimentological criteria. Ph.D.-thesis, P&G, Stockholms Universitet, 124 pp. Note about the dating systems used in this book In this book, I discuss dates derived from both varves and radiocarbon. For distinction, I label varve-ages with vBP and C14-ages with cBP.