Earthquake Occurrence and Seismotectonics in Norway and Surrounding Areas

Bungum, Hilmar

doi:10.1007/978-94-009-2311-9_29

Cited by 18 publications

(5 citation statements)

References 26 publications

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“…In addition to the postglacial uplift, there are two main sources of evidence of neotectonics in Scandinavia: the recent earthquake record, and the observation of movement along faults (e.g. Husebye et al, 1978;Olesen, 1988;Bungum, 1989;Olesen et al, 1992 and1995). Local instrumentation can now record small earthquakes of magnitude 2, as summarised on a neotectonics map by Dehls et al (2000a).…”

Section: Neotectonicsmentioning

confidence: 99%

Tectonic Inception in Caledonide Marbles

Faulkner

2006

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Trevor Faulkner: Tektonska incepcija v kaledonskih marmorjih V centralni Skandinaviji je več kot tisoč izdankov marmorja v katerih je znanih preko tisoč jam. Razlika med temi jamami in tistimi v apnencih, je pogojena s procesi metamorfoze in zanemarljivo primarno poroznostjo prvih. S tem je povezano drobno plastenje (foliacija) in posledična odsotnost lezik. Najgloblja jama je globoka 180 m, kljub temu, da vertikalni razpon izdankov znaša do 900 m. Jame največkrat najdemo v skupinah in so v vertikalnem merilu precej naključno porazdeljene, pri čemer jih redko najdemo več kot 50 m pod površjem. Kljub temu, da so nekateri izdanki pasastega krasa dolgi več deset kilometrov, zelo dolgih jam ne poznamo, kraški hidrološki sistemi pa ne presegajo dolžine 3.5 km. Ker so jame kratke in blizu površja, je kemijska incepcija manj verjetna. Zato predlagam model tektonske incepcije, ki predvideva, da so jame v kaledonskih marmorjih nastale zgolj vzdolž sistemov odprtih razpok, pri čemer je dimenzija in frekvenca teh razpok povezana z magnitude tektonskih premikov, ki so nastali kot posledica izostatičnega uravnoteženja ob umikih ledenikov po ledenih dobah. Sistemi takih razpok so nastajali vzdolž incepcijskih površin med marmorji in neprepustnimi plastmi in vzdolž incepcijskih razpok v marmorjih, ki so vzporedne ali pravokotne s plastenjem. Model gradim tudi na poročilih o delno odcepljenem tankem vrhnjem delu skorje v podobnih okoljih na Škotskem. Model podpirajo tudi opažanja kasnejših neotektonskih premikov, na katere kažejo ostri robovi in tektonska zrcala v jamah in na površju.

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Section: Neotectonicsmentioning

confidence: 99%

Tectonic Inception in Caledonide Marbles

Faulkner

2006

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“…For longer times, the stress is relaxed 696 G. Spada et al in the whole planet, as for the uniform viscosity model. For B 2 50, the maximum shear stress in the lithosphere can be as high as 100bar and pre-existing faults induced by a previous tectonics, such as the opening of the North-Atlantic, can be reactivated by the unloading event (Stein et al 1979;Hasegawa & Hermann 1989;Bungum 1989). These results indicate that the existence of an active seismicity around deglaciated areas requires a substantial viscosity increase in the lower mantle, in agreement with recent findings from Holocene rebound data and sea-level fluctuations in NW Europe (Lambeck et al 1990).…”

Section: Stress Fields In the Lithosphere A N D Upper Mantlementioning

confidence: 99%

Effects on post-glacial rebound from the hard rheology in the transition zone

Spada¹,

Sabadini²,

Yuen³

et al. 1992

Geophysical Journal International

112

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We analyse the influences of a viscosity increase in the transition zone between 420 and 670 km on the geophysical signatures induced by post-glacial rebound, ranging from the perturbations in the Earth's rotation to the short wavelength features associated with the migration of the peripheral bulge. A self-gravitating model is adopted, consisting of an elastic lithosphere, a three-layer viscoelastic mantle and an inviscid core.\ud \ud The horizontal displacements and velocities and the stress pattern are extremely sensitive to the viscosity increase and to the chemical stratification of the transition zone. The hardening of the upper and the chemical density jumps in mantle below the 420 discontinuity induces a channel effect which contaminates the horizontal deformation both in the near-field and in the far-field from the ice-sheets. These findings indicate that intraplate geodetic data can be used to put bounds on the viscosity increase in the transition zone and on the amount of chemical stratification in the mantle.\ud \ud The stress field induced in the lithosphere by the Pleistocenic ice-sheet disintegration is a very sensitive function of mantle viscosity stratification. The existence of seismic activity along passive continental margins of previously glaciated areas requires a substantial viscosity increase in the mantle, with the viscosity of the transition zone acting as a controlling parameter. A viscously stratified mantle is responsible for a delayed upward migration of stress in the lithosphere which can account for the seismicity today

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“…Although Northern Europe is in an intraplate seismotectonic environment, it experiences earthquakes up to magnitude 6 (Bungum 1989;Slunga 1989;WahlstrÎm 1989;Arvidsson & Kulhanek 1994). Furthermore, during late glacial and early postglacial times, Fennoscandia and the British Isles appear to have been seismically more active and events as large as magnitude 8 could have occurred (Arvidsson 1996).…”

Section: Introductionmentioning

confidence: 99%

Dependence of horizontal stress magnitude on load dimension in glacial rebound models

Johnston

Lambeck

2002

Geophysical Journal International

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Summary It has been proposed that the deglaciation of the Northern Hemisphere triggered large earthquakes within intraplate environments and in this paper we examine this hypothesis by evaluating quantitatively the stress state in the lithosphere produced by time‐dependent surface loads. A series of models demonstrate the dependence of horizontal incremental stress in an elastic plate overlying an inviscid or viscoelastic mantle on the lateral extent of a load applied at the surface. The horizontal stress is largest when the dominant wavelength (that is twice the diameter) of the load is close to eight times the elastic thickness of the plate when the mantle is inviscid and, for the particular viscosity model employed in this paper, close to 12 times the elastic thickness for a viscoelastic mantle. At wavelengths close to the critical wavelength, the horizontal incremental stress may be up to six times as large as the vertical incremental stress. For appropriate earth‐model parameters amplification of horizontal stress is close to maximum for ice loads with a radius of 280 km, comparable to the dimensions of the former ice sheet over Great Britain. This amplification may be sufficiently large that loading by small ice sheets can lead to failure on marginally stable faults, in contrast to the behaviour for large ice sheets. The models also predict greater fault instability for Fennoscandia than for the larger Laurentide ice sheet, consistent with the observation of large postglacial faults in northern Sweden. The model is used to predict the stability of faults and style of faulting due to rebound stresses in the absence of a background tectonic stress field since the last glacial maximum (∼ 18 000 years ago) in Northern Europe. Within the formerly glaciated region thrust faulting is predicted to occur at the end of deglaciation and normal faulting is predicted to occur in peripheral regions for the entire period since the last glacial maximum.

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Earthquake Occurrence and Seismotectonics in Norway and Surrounding Areas

Cited by 18 publications

References 26 publications

Tectonic Inception in Caledonide Marbles

Tectonic Inception in Caledonide Marbles

Effects on post-glacial rebound from the hard rheology in the transition zone

Dependence of horizontal stress magnitude on load dimension in glacial rebound models

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