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Dauteuil O., Tournat F., Bouffette J., Van Vliet-Lanoë, B. , Embry J.C., Quete Y , Lefevre A. |
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Finite Holocene deformation outside the rift zone of North Iceland. |
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2005 |
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Tectonophysics |
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404 |
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203-216 |
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316 |
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0040-1951 |
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4102 |
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BERGERAT F. et ANGELIER J. |
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Immature and mature transform zones near a hot spot: the South Iceland Seismic Zone and the Tjörnes Fracture Zone (Iceland). |
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2008 |
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Tectonophysics |
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447 |
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142-154 |
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316 |
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0040-1951 |
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4105 |
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Author |
Corchete V, |
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Title |
Shear-wave velocity structure of Antarctica from Rayleigh-wave analysis
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Journal Article |
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Year |
2013 |
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Tectonophysics |
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583 |
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1-15 |
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Keywords |
Rayleigh wave, Shear wave, Crust, Upper mantle, Antarctica, |
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133 |
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0040-1951 |
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4650 |
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Bergerat Françoise, Homberg Catherine, Angelier Jacques, Bellou Magalie, |
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Title |
Surface traces of the Minnivellir, Réttarnes and Tjörvafit seismic faults in the South Iceland Seismic Zone: Segmentation, lengths and magnitude of related earthquakes
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Journal Article |
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2011 |
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Tectonophysics |
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498 |
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14 |
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11-26 |
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Keywords |
South Iceland Seismic Zone, Transform zone, Paleoseismic fault, Fault segmentation, Offset fault vs. earthquake magnitude, Riedel-type fault pattern, |
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316 |
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Bachelor's thesis |
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0040-1951 |
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yes |
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3740 |
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Author |
Plateaux Romain, Bergerat Françoise, Béthoux Nicole, Villemin Thierry, Gerbault Muriel, |
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Title |
Implications of fracturing mechanisms and fluid pressure on earthquakes and fault slip data in the east Iceland rift zone
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Journal Article |
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2011 |
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Tectonophysics |
Abbreviated Journal |
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- |
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Icelandic rift, Stress permutation, Volcano-tectonics, Paleostresses, Fluid pore pressure, Fracturing mechanisms, |
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Abstract |
Comparison of the eroded off-rift zone left inactive by plate motion with the inner active seismic rift zone allows us to constrain the fracturing mechanisms. In eastern off-rift zone, we measured 423 fault slips (including normal and strike-slip faults). Inversion of fault slip data reveals the parallelism of the minimum stress (3) computed for the normal and for the strike-slip faulting, and consistency with the direction of plate divergence. North of the Vatnajökull, in the active rift zone, we analysed 14,250 earthquakes recorded by the Icelandic Meteorological Office (IMO) between 2004 and 2009, especially northeast of the Askja volcano. Two main average focal depths were determined at 5 km (Herðubreið table mountain) and 15 km (Upptyppingar hyaloclastite ridge). The double couple focal mechanisms determined by IMO revealed that more than half of the mechanisms are strike-slip. Faulting type both in active and off-rift zone reveals an unusual importance of strike-slip regime in such an extensional tectonic context. This can be explained by stress permutations (1/2). Similarities in terms of stress orientations and type of faulting are observed both in the old and present-day rift zones. We assume that the seismic events may be generated by rapid deep magma intrusion, also associated with shallower hydrothermal activities. We thus propose that the presence of fluids, shear failure (double couple focal mechanism) and stress permutations in both active and off-rift zones are closely linked. Assuming a DruckerPrager failure criterion, we evaluated analytically that a state near of lithostatic pore pressure is a necessary condition for shear failure at shallow (5 km) and deep (15 km) depth, in a simple context of crustal extension that allows for stress permutations. However, processes favouring stress permutations cannot be further constrained from our observations since the dynamics of fluid, materiel heterogeneity and post-glacial rebound can also play a significant role. |
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316 |
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0040-1951 |
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yes |
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Serial |
3755 |
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Author |
Célérier Bernard, Etchecopar Arnaud, Bergerat Françoise, Vergely Pierre, Arthaud François, Laurent Philippe, |
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Title |
Inferring stress from faulting: From early concepts to inverse methods
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Journal Article |
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2012 |
Publication |
TECTONOPHYSICS |
Abbreviated Journal |
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Volume |
581 |
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206-219 |
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Keywords |
Fault and slip, Faulting, Inverse methods, Stress, |
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Abstract |
We review the evolution of concepts on and methods of estimating the state of stress from fault movements. Theories of failure in isotropic materials suggested a simple geometrical construction of optimal principal stress directions from a fault plane and its associated slip. These optimal directions align shear stress and slip directions and maximize the difference between shear stress and frictional resistance on the fault plane. Optimal stress directions for calcite twinning are obtained by a similar construction, with the difference that they maximize shear stress. Force representation of seismic sources independently introduced pressure, P, and tension, T, axes at positions that also maximize shear stress on both nodal planes. |
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316 |
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0040-1951 |
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yes |
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Serial |
4259 |
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Author |
Bascou Jérôme, Henry Bernard, Ménot René-Pierre, Funaki Minoru, Barruol Guilhem, |
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Title |
Contribution of AMS measurements in understanding the migmatitic terrains of Pointe Géologie, Terre Adélie (East-Antarctica)
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Journal Article |
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Year |
2013 |
Publication |
Tectonophysics |
Abbreviated Journal |
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603 |
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123-135 |
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A detailed magnetic mapping using Anisotropy of Magnetic Susceptibility (AMS) technique was carried out in Pointe Géologie archipelago (Terre Adélie, East Antarctica) that represents a hot crust having experienced a long-lived anatectic event during Paleoproterozoic times, 1.69 Ga ago. AMS measurements allowed to better analyse the tectonic structure of the crystalline basement that is built up by rocks affected by various degrees of partial melting and then, devoid of clear strain markers. AMS sampling was performed from main rocks types of Pointe Géologie: migmatites including leucosomes and melanosomes, coarse-grained pink granites, anatexites and mylonitic gneisses. For melanosomes, the magnetic foliation is dominantly in agreement with the observed field foliation, i.e. dominantly N–S sub-vertical in shear zones and gently inclined in dome structures. AMS technique reveals a sub-horizontal magnetic lineation in migmatites from shear zones and a gently plunging one in dome structures. Magnetic properties of leucosomes and of coarse-pink granitic dykes contrast with melanosomes. The bulk susceptibility and anisotropy degree are significantly lower in granitic magmas that in melanosomes. In addition, in well-defined leucosomes, granitic dykes and anatexites, the magnetic ellipsoid is characterized by a higher plunge of the magnetic lineation, which tends to be vertical. This is associated to a rheological contrast between the solid-state deformation suffered by oxide grains in the melanosomes and their reorientation in a viscous flow during the transfer of felsic melt to the granitic dykes. Magnetic structure of leucosomes, granitic dykes and anatexites highlights the role of the gravity-induced upwelling of a crust undergoing high degree of partial melting in a transpressional regime. |
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1003 |
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0040-1951 |
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yes |
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4779 |
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Author |
Chang Sung-Joon, Ferreira Ana MG, Ritsema Jeroen, van Heijst Hendrik J, Woodhouse John H, |
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Title |
Global radially anisotropic mantle structure from multiple datasets: A review, current challenges, and outlook
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Journal Article |
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2014 |
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Tectonophysics |
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617 |
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1-19 |
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Keywords |
Radial anisotropy, Group velocity, Crustal corrections, Tomography, LPO, SPO, |
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133 |
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0040-1951 |
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yes |
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5092 |
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Gaëlle Lamarque, Jérôme Bascou, Claire Maurice, Jean-Yves Cottin, Nicolas Riel, René-Pierre Ménot |
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Title |
Microstructures, deformation mechanisms and seismic properties of a Palaeoproterozoic shear zone: The Mertz shear zone, East-Antarctica |
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Journal |
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Year |
2016 |
Publication |
Tectonophysics |
Abbreviated Journal |
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Volume |
680 |
Issue |
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Pages |
174-191 |
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Keywords |
Crustal deformation Crystallographic preferred orientation (CPO) East Antarctica Microstructures Shear zone Strain localization |
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Abstract |
The Mertz shear zone (MSZ) is a lithospheric scale structure that recorded mid-crustal deformation during the 1.7Ga orogeny. We performed a microstructural and crystallographic preferred orientation (CPO) study of samples from both mylonites and tectonic boudins that constitute relics of the Terre Adélie Craton (TAC). The deformation is highly accommodated in the MSZ by anastomosed shear bands, which become more scattered elsewhere in the TAC. Most of the MSZ amphibolite-facies mylonites display similar CPO, thermal conditions, intensity of deformation and dominant shear strain. Preserved granulite-facies boudins show both coaxial and non-coaxial strains related to the previous 2.45Ga event. This former deformation is more penetrative and less localized and shows a deformation gradient, later affected by a major phase of recrystallization during retrogression at 2.42Ga. Both MSZ samples and granulite-facies tectonic boudins present microstructures that reflect a variety of deformation mechanisms associated with the rock creep that induce contrasted CPO of minerals (quartz, feldspar, biotite, amphibole and orthopyroxene). In particular, we highlight the development of an “uncommon” CPO in orthopyroxene from weakly deformed samples characterized by (010)-planes oriented parallel to the foliation plane, [001]-axes parallel to the stretching lineation and clustering of [100]-axes near the Y structural direction. Lastly, we computed the seismic properties of the amphibolite and granulite facies rocks in the MSZ area in order to evaluate the contribution of the deformed intermediate and lower continental crust to the seismic anisotropy recorded above the MSZ. Our results reveal that (i) the low content of amphibole and biotite in the rock formations of the TAC, and (ii) the interactions between the CPO of the different mineralogical phases, generate a seismically isotropic crust. Thus, the seismic anisotropy recorded by the seismic stations of the TAC, including the MSZ, must be due to mantle rather than crustal structures. |
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1003 |
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0040-1951 |
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0040-1951 |
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yes |
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6748 |
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Author |
Lev Vinnik, Elena Kozlovskaya, Sergey Oreshin, Grigoriy Kosarev, Katerina Piiponen, Hanna Silvennoinen |
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Title |
The lithosphere, LAB, LVZ and Lehmann discontinuity under central Fennoscandia from receiver functions |
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2016 |
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Tectonophysics |
Abbreviated Journal |
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667 |
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189-198 |
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Keywords |
LAB Lehmann discontinuity Low-velocity zone Partial melting Receiver functions Seismic anisotropy |
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Abstract |
P- and S-wave velocity profiles (Vp and Vs) from the Earth's surface to a depth of 300km are obtained by simultaneous inversion of P- and S-wave receiver functions for the temporary POLENET/LAPNET array in northern Finland and 5 permanent stations in southern Finland. The obtained Vp/Vs velocity ratio in the uppermost mantle is anomalously low (1.65–1.70 versus the standard 1.8). This ratio can be explained by a high (~30%) fraction of orthopyroxene in the depleted upper mantle. An increase of ~4% in the Vs values is detected at a depth of 110–130km. Under southern Finland the high-velocity mantle keel may extend beyond the depth of 300km, but under northern Finland we detect a low-Vs zone (LVZ) with the top at a depth of 160km. This depth corresponds to the intersection of the geotherm with the wet solidus of peridotite at a temperature near ~1100°C, and suggests partial melting as an explanation for the origin of the LVZ. The bottom of the LVZ (the Lehmann discontinuity) is found at a depth of 240km. The fast direction of seismic azimuthal anisotropy beneath northern Finland in the depth interval from 200–240km to 320km is parallel to the current APM direction (60°) but in the interval from 160km to 200–240km the fast direction (150°) appears to be normal to the APM direction (Vinnik et al., 2014). The present study indicates that the fast direction of 150° confines to the LVZ where the flow in the direction normal to the APM direction is unlikely. More likely, the flow direction is parallel to the APM direction and normal to the fast direction of anisotropy, as suggested by experiments with sheared peridotite-type rocks containing melt. |
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1021 |
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0040-1951 |
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8166 |
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