Éditeur(s) : HAL CCSD Geological Society of America
Résumé : International audience
The post-rift denudation history of high-elevation divergent continental margins is central to deciphering source-to-sink systems across such margins and to unraveling their topographic evolution. We performed 40Ar-39Ar dating of supergene K-Mn oxides from supergene manganese ore deposits in order to constrain the age of in situ formed laterites on both the lowland and highland sides of the Western Ghats Escarpment of Peninsular India. Documentation of laterites as old as 53 Ma on the highland and 47 Ma at the foot of the escarpment shows that the escarpment stabilized before 47 Ma (possibly 60 Ma). The topographic setting of the dated weathering mantles also constrains denudation of the lowland and the highland since ca. 50 Ma to maximums of 5 m/m.y. and 15 m/m.y., respectively. Our results challenge denudation rates derived from apatite fission track thermochronology by documenting the topography and relief longevity of the southwest Indian margin and its hinterland. The results preclude large-magnitude uplift of Peninsular India after the Eocene, and more generally argue against late Neogene uplift and topographic rejuvenation of continental shields.
ISSN: 0091-7613

hal-01306559
https://hal.archives-ouvertes.fr/hal-01306559
DOI : 10.1130/G37303.1

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Located in central Europe at the junction of the Southern Alps and the Dinarides, the ≈ 100 km long Idrija fault, striking N310 and dipping ≈ 80°NE is often considered as the potential source of the historical 1511 earthquake (estimated macroseismic magnitude: Mm 6.8). Using 1/25,000 to 1/5000 topographical maps, satellite images (SPOT5), 12.5 m illuminated DEM and airborne LiDAR data-derived 1-m-DEM, we examined in detail the Idrija fault trace along a 20-km-long swath in the central portion of the fault. Combining topographic and remote sensing data allows characterizing the recent activity along the Idrija fault and estimating its cumulative displacement along strike.Between Tolmin and Godovič, the fault trace is mostly linear but appears divided into three disconnected segments of 11–20-km-long. Morphological evidences such as offset streams and ridges and major drainage abandonments suggest ongoing movement. At three sites, field observations and LiDAR-DEM analysis allow measuring cumulative dextral offsets comprised between 35 and 65 m. We found two larger offsets of ≈ 140 m and ≈ 360 m at the southeasternmost site. The vertical component is significant and revealed by a rake ranging from 0 to 33°. The derived N303–N310 striking slip-vector is in agreement with the motion along this fault as suggested by the geodesy. Assuming that the smallest measured offsets have been recorded after the last glacial maximum (LGM, about 20 ka ago), the minimum slip-rate for the Idrija fault is about 1.5 mm/yr over this period of time.
ISSN: 0040-1951

hal-01115724
https://hal.archives-ouvertes.fr/hal-01115724
DOI : 10.1016/j.tecto.2014.04.043

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
During the last decade, the interaction of deep processes in the lithosphere and mantle with surface processes (erosion, climate, sea-level, subsidence, glacio-isostatic readjustment) has been the subject of heated discussion. The use of a multidisciplinary approach linking geology, geophysics, geodesy, modelling, and geotechnology has led to the awareness of coupled deep and surface processes. Deep earth dynamics (topography, erosion, tectonics) are strongly connected to natural hazards such as earthquakes, landslides, and tsunamis; sedimentary mass transfers have important consequences on isostatic movements and on georesources, geothermal energy repartitions. The ability to read and understand the link between deep Earth dynamics and surface processes has therefore important societal impacts. Ground-truthing at carefully-selected sites of investigation is imperative to better understand these connections.Due to its youth (<30 Ma) and its subsidence history, the almost land-locked Gulf of Lion–Sardinia continental margins system provides a unique record of sedimentary deposition from the Miocene to present. Due to its high subsidence rate, palaeoclimatic variations, tectonic events and vertical evolution are all recorded here at very high resolution. The late Miocene isolation and desiccation of the Mediterranean, the youngest and most catastrophic event, the Messinian Salinity Crisis (MSC), induced drastic changes in marine environments: widespread deposition of evaporite (gypsum, anhydrite and halite) in the central basin, and intense subaerial erosion along its periphery. These extraordinary mass transfers from land to sea induced strong isostatic re-adjustments that are archived in the sedimentary record and represent a window to the lithospheric rheology and the deep processes.The GOLD (Gulf of Lion Drilling) project, proposes to explore this unique sedimentary record as well as the nature of the deep crustal structure, providing valuable information about the mechanisms underlying vertical motions in basins and their margins.
ISSN: 0264-8172

insu-01197393
https://hal-insu.archives-ouvertes.fr/insu-01197393
https://hal-insu.archives-ouvertes.fr/insu-01197393/document
https://hal-insu.archives-ouvertes.fr/insu-01197393/file/Rabineau%20et%20al.-final-MPG2014_REVISED-FINAL-No-Marked_FINAL%2BFigures.pdf
DOI : 10.1016/j.marpetgeo.2015.03.018

Éditeur(s) : s.n. ( El Salvador, El Salvador )
Résumé : (Language) In Spanish and English.
El Salvador.
Shows grid.
Information presented on this map and in accompanying text is based on existing vegetation maps 1:50,000 topographic series compiled photogrammetrically, 1:50,000 soil studies, materials furnished by the Dirección General de Agricultura in June 1964, andvarious U. S. sources.
"Alianza para el Progreso".
El Salvador
El Salvador

642642072
http://ufdc.ufl.edu/UF00103168/00001

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : Rock foundations of the Kephren and Kheops pyramids are examined in comparison with other Fourth Dynasty monuments: the Sphinx, Queen Kentkawes' monument and the Abu Rawash monument. This study is based on geological and topographical observations, photomontages and field measurements. The results, which are correlated with those of former studies, demonstrate the existence of natural hills used as substrata in the construction of the two great pyramids. The minimum volume of these hills can be estimated at 12% and 23% respectively of the volumes of the Kephren and Kheops pyramids. The use of worked rock hills appears to be a construction method under the Fourth Dynasty.
EISSN: 1777-5817

hal-00512644
https://hal.archives-ouvertes.fr/hal-00512644

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Deep-seated gravitational spreading (DSGS) affects the slopes of formerly glaciated mountain ridges. On Mars, DSGS has played a key role in shaping the landforms of the giant Valles Marineris troughs. Though less spectacular, DSGS is common in terrestrial orogens, where understanding its mechanics is critical in the light of the ongoing climate change because it is a potential source of catastrophic landslides in deglaciated valleys. We conducted parametric numerical studies in order to identify important factors responsible for DSGS initiation. DSGS models are computed using an elastoviscoplastic finite element code. Using ADELI's software, we reproduce topographic ridge spreading under the effect of valley unloading. Two types of spreading topographic ridges are investigated, homogeneous or with horizontal rheological layering. We find that gravitational instabilities are enhanced by high slopes, which increase gravitational stress, and low friction and cohesion, which decrease yield stress. In the unlayered ridge, instability is triggered by glacial unloading with plastic strain concentration inside the ridge and at the base of the high slopes. Vertical fractures develop in the upper part of the slope, potentially leading to fault scarps. Ridge homogeneity promotes a deformation mode controlled by uphill-facing normal faulting and basal bulging. In the second case, the ridge encompasses horizontal geological discontinuities that induce rock mass anisotropy. Discontinuity located at the base of the slope accumulates plastic strain, leading to the formation of a sliding plane evolving into a landslide. The presence of a weak layer at ridge base therefore promotes another slope deformation mode ending up with catastrophic failure. Mechanical conditions and slope height being equal, these conclusions can probably be extrapolated to Earth. Compared with Mars, DSGS on Earth is inhibited because terrestrial topographic gradients are lower than in Valles Marineris, an effect counterbalanced by increased gravitational stress, where the intensity of deformation is enhanced because of the Earth gravity potential.
ISSN: 0169-555X

hal-01420007
https://hal.archives-ouvertes.fr/hal-01420007
DOI : 10.1016/j.geomorph.2016.06.011

Éditeur(s) : Neidine editeurs
Résumé : This text is focused on the popularization of the general public, edited in a magazine connected to the sea. It explicits, in first part, all the factors which make that the surface of the sea is not horizontal. In second part are introduced the principles of the satellite altimetry which allows to measure the slope of the surface of the sea which, because of the variations of Earth' attraction from a point to an other, is directly connected to the topography of the bottom of the oceans. After a historical review of the various altimeter satellite missions launched from the beginning of 1970s to our days, the text discusses the applications allowed by the topographic images of the bottom of seas and the progress that these spatial technologies have offered, regarding the knowledge of the world oceanic domain.
Ce texte de vulgarisation à destination du grand public, édité dans un magazine lié à la mer, explicite en première partie l'ensemble des facteurs qui font que la surface de la mer n'est pas horizontale. En seconde partie sont introduits les principes de l'altimétrie satellitaire qui permet de mesurer la pente de surface de la mer qui elle même, en raison des variations d'attraction terrestre d'un point à un autre, est directement liée à la topographie du fond des océans. Après un rappel historique des différentes missions altimétriques réalisées du début des années 1970 à nos jours, le texte discute des applications que les images topographiques du fond des mers ont permis de développer et les progrès que ces technologies spatiales ont offert en matière de connaissance du domaine océanique sous marin mondial.
Taï Kona (2269-7535) (Neidine editeurs), 2013-05 , N. 2 , P. 34-41

Droits : Tai Kona
http://archimer.ifremer.fr/doc/00142/25351/23433.pdf
http://archimer.ifremer.fr/doc/00142/25351/

Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : International audience
Surface displacements due to temporal changes in environmental mass redistributions are observable in the coordinate time series of many Global Navigation Satellite System (GNSS) sites. In this study, we investigated the effect of loading on estimates of tectonic velocity computed from campaign-style GNSS observations. The study region is in the Pyrenees mountain range between France and Spain (ResPyr campaigns). In this area, seismic activity is continuous and moderate and the expected amplitude of the horizontal tectonic velocity is less than 0.5 mm/yr. In order to determine the velocity, 4 sparse GNSS campaigns were carried out from 1995 to 2010. Considering this small rate of deformation, loading phenomena can contribute a non-negligible artifact to the velocity computation that could affect our geodynamical interpretation. In this investigation, we specifically considered the atmospheric, hydrological, and non-tidal ocean loading phenomena. The computed loading deformations for this region show the horizontal displacements are dominated by the non-tidal ocean loading (maximum 4 mm for the North and 3.1 mm for the East components); the main vertical contributions are due to the atmospheric and continental water storage loading (maximum 14.3 for the atmosphere and 8.1 mm for the hydrology, respectively). We have found that the dominant loading effect on the horizontal velocity is the non-tidal ocean loading (mean of 0.11 mm/yr), whereas the vertical component is dominated by the hydrological loading (mean of 0.21 mm/yr). Since the study area is in a mountainous region, we also analyzed the difference between the atmospheric and the topography dependent atmospheric loading models at our GNSS campaign sites. We did not find any significant difference between the two atmospheric loading models in terms of horizontal velocity. Finally, we performed simulations to identify the optimum timing and frequency of future GNSS campaigns in this area that would minimize the loading effects on tectonic velocity estimates.
ISSN: 0039-3169

hal-00963629
https://hal.archives-ouvertes.fr/hal-00963629
DOI : 10.1007/s11200-012-0458-2

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : In habitat mosaics, plant populations face environmental heterogeneity over short geographical distances. Such steep environmental gradients can induce ecological divergence. Lowland rainforests of the Guiana Shield are characterized by sharp, short-distance environmental variations related to topography and soil characteristics (from waterlogged bottomlands on hydromorphic soils to well-drained terra firme on ferralitic soils). Continuous plant populations distributed along such gradients are an interesting system to study intrapopulation divergence at highly local scales. This study tested (1) whether conspecific populations growing in different habitats diverge at functional traits, and (2) whether they diverge in the same way as congeneric species having different habitat preferences. Phenotypic differentiation was studied within continuous populations occupying different habitats for two congeneric, sympatric, and ecologically divergent tree species (Eperua falcata and E. grandiflora, Fabaceae). Over 3000 seeds collected from three habitats were germinated and grown in a common garden experiment, and 23 morphological, biomass, resource allocation and physiological traits were measured. In both species, seedling populations native of different habitats displayed phenotypic divergence for several traits (including seedling growth, biomass allocation, leaf chemistry, photosynthesis and carbon isotope composition). This may occur through heritable genetic variation or other maternally inherited effects. For a sub-set of traits, the intraspecific divergence associated with environmental variation coincided with interspecific divergence. The results indicate that mother trees from different habitats transmit divergent trait values to their progeny, and suggest that local environmental variation selects for different trait optima even at a very local spatial scale. Traits for which differentiation within species follows the same pattern as differentiation between species indicate that the same ecological processes underlie intra- and interspecific variation.
ISSN: 0305-7364

hal-01032430
https://hal.archives-ouvertes.fr/hal-01032430
DOI : 10.1093/aob/mct176

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
The seismic behavior of the Himalayan arc between central Nepal and Arunachal Pradesh remains poorly understood due to the lack of observations concerning the timing and size of past major and great earthquakes in Bhutan. We present here the first paleoseismic study along the Himalayan topographic front conducted at two sites in southern central Bhutan. Paleoseismological excavations and related OxCal modeling reveal that Bhutan experienced at least two great earthquakes in the last millennium: one between the seventeenth and eighteenth century and one during medieval times, producing a total cumulative vertical offset greater than 10 m. Along with previous studies that reported similar medieval events in Central Nepal, Sikkim, and Assam, our investigations support the occurrence of either (i) a series of great earthquakes between A.D. 1025 and A.D. 1520 or (ii) a single giant earthquake between A.D. 1090 and A.D. 1145. In the latter case, the surface rupture may have reached a total length of ~800 km and could be associated with an earthquake of magnitude Mw = 8.7–9.1.
ISSN: 0148-0227

hal-01622276
https://hal.archives-ouvertes.fr/hal-01622276
DOI : 10.1002/2015JB012733

Éditeur(s) : HAL CCSD Blackwell Publishing
Résumé : International audience
In the Causses platform (south-east France), Late Hettangian to Sinemurian deposits were interpreted previously as shallow-water carbonate ramp deposits. A new look at these deposits has shown a fault-controlled mosaic carbonate platform that is different from the carbonate ramp models. Within the platform mosaic, 15 lithofacies have been recognized, which are organized in four facies associations, including peritidal, restricted shallow sub-tidal, sand dunes and sub-tidal shelf facies associations. The rapid lateral and vertical facies changes, and the lack of consistent landward or seaward direction indicated by the pattern of facies changes, question the existence of a shoreline suggested by the traditional models for this region. Instead, the facies organization and cycle stacking pattern suggest deposition in a mosaic of intertidal islands between which sub-tidal restricted or open conditions could coexist in very close proximity. Such a platform mosaic would have been defined by tectonic activities along normal faults which segmented the shallow-water Causses platform. The facies and facies associations are arranged into metre-scale, peritidal and sub-tidal cycles that are also variable. Certain cycles show the same stacking pattern in all the sections and seem to be traceable over tens of kilometres. On the contrary, other cycles cannot be correlated; they are present only in specific sections and have a maximum lateral extension of 1 or 2 km. These metre-scale cycles stack to form four medium-scale cycles bounded by surfaces that display sub-aerial exposure features. Medium-scale cycles stack into two larger-scale cycles (tens of metres thick) and are bounded by well-defined karstic surfaces. Based on their lateral continuity and their stacking pattern, the metre-scale cycles are controlled probably by high frequency eustatic variations overprinting the topographic irregularities formed by differential subsidence of fault-bounded blocks. Episodic fault activities may reorganize the topography so that, even if eustatic changes may still be the major control of cycles, the expression and number of cycles could be different. Cycles of medium and large-scale are interpreted as being allogenic, controlled by changes in eustasy and/or subsidence rates as evidenced by their lateral continuity and the correlations of the large-scale cycles with third-order depositional sequences.
ISSN: 1469-3496

hal-00411940
https://hal.archives-ouvertes.fr/hal-00411940
DOI : 10.1111/j.1365-3091.2007.00896.x

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
S U M M A R Y Over the last decade, thermomechanical models have revealed the control of both tectonics and erosion on the morphology of continental plateaus margins. However, unravelling the specific effects of these two coupled processes has been difficult in practice. Here, to assess the control of erosion, we investigate the dynamics of the eastern and the northern borders of the Tibetan Plateau, which are characterized by a low convergence rate and a steep topographic escarpment adjacent to the Sichuan and Tarim basins, respectively. Thermomechanical modelling of continental lithosphere coupled with fluvial denudation reveals that important crustal deformation with large-scale horizontal displacements can occur, without any convergence, as a response to mass transfer due to gravitational collapse and to erosional unloading. These processes are sensitive to crustal structure, geothermal gradient as well as surface erosion. At a timescale of several million years, our results suggest that this denudation-triggered deformation exerts a primary control on the evolution of those plateau margins by counterbalancing the mass removal due to erosion and stabilizing the topographic escarpment. This finding supports a possible explanation for the morphology of the Longmen Shan, eastern Tibet, in which the paradoxical combination of persistent high-topographic gradients close to the foreland and low convergence rates can be related to the influence of erosion on deformation patterns.
ISSN: 0956-540X

hal-01577060
https://hal-amu.archives-ouvertes.fr/hal-01577060
https://hal-amu.archives-ouvertes.fr/hal-01577060/document
https://hal-amu.archives-ouvertes.fr/hal-01577060/file/godard2009erosional.pdf
DOI : 10.1111/j.1365-246X.2009.04324.x

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
Apatite fission track analysis (AFTA) data are used to bring new light on the long-term and recent history of the Baikal rift region (Siberia). We describe the evolution of the topography along a NW-SE profile from the Siberian platform to the Barguzin range across the Baikal-southern Patom range and the northern termination of Lake Baikal. Our results show that the Baikal-Patom range started to form in the Early Carboniferous and was reactivated in Middle Jurassic-Lower Cretaceous times during the orogenic collapse of the Mongol-Okhotsk belt. Samples located in the Siberian platform recorded a continuous sedimentation up to the early Carboniferous but remain unaffected by later tectonic episodes. The Barguzin basin probably started to form as early as Late Cretaceous, suggesting a continuum of deformation between the postorogenic collapse and the opening of the Baikal Rift System (BRS). The initial driving mechanism for the opening of the BRS is thus independent from the India-Asia collision. AFTA show a late Miocene-early Pliocene increase in tectonic extension in the BRS that confirms previous thoughts and might reflect the first significant effect of the stress field generated by the India-Asia collision.
ISSN: 0278-7407

hal-00420895
https://hal.archives-ouvertes.fr/hal-00420895
DOI : 10.1029/2008TC002404

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Fractures or discontinuities perpendicular to the least stress σ3 were generated in a synthetic rock analogue (granular, frictional, cohesive, and dilatant) material in axisymmetric extension tests. These fractures are of two types defined by the mean stress σ. When σ is very small, the fractures form through the mode I cracking at tensile σ3 equal to the material tensile strength. The fracture walls have smooth surfaces. At higher σ, these surfaces become rougher, with the topography features forming faint or delicate plumose patterns. The amplitude of the plumose topography increases with σ. The axial stress σ3 at fracturing reduces in magnitude and changes in sign with the σ increase. Thus σ3 orthogonal discontinuities can form at compressive σ3. SEM observations show that these discontinuities are deformation localization bands where the material is characterized by the heterogeneous decohesion and volume and porosity increase due to dilatancy. The band thickness is several grain sizes. At formation, the bands are not opened, so they are not mode I fractures. They become fractures with plumose fractography after the separation of the sample parts along the band. The formation mechanism of these discontinuities or fractures is not completely clear, but it is suggested that it represents a running constitutive instability in the form of dilatancy banding (with further σ increase the bands become inclined to σ1, i.e., shear). The similarity between the experimentally generated plumose surface fractures and natural joints is discussed, and it is suggested that they can be formed as propagating constitutive instabilities.
ISSN: 0148-0227

hal-00585846
https://hal.archives-ouvertes.fr/hal-00585846
DOI : 10.1029/2010JB008104

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In southeastern Taiwan a slice of forearc basement belonging to the Philippine Sea Plate upper-plate is suspected to subduct under the Luzon arc as a consequence of the transition from oceanic to incipient continental subduction. Effects on the morphology, deformation, geometry of structures and tectonic evolution of the orogenic wedge in the collision area are numerous. This study examines the impact of foreare lithosphere subduction on forearc basin and accretionary wedge deformation. A morpho-structural analysis of the geological features observed onland and offshore allows describing in detail the complex deformation suffered by the area. A combined approach by analogue modeling is applied to better understand the phenomenon. Comparison between nature and experimental results shows that subduction of a forearc basement slice induces intense shortening and concomitant deformation in the foreare domain. Such process involves deformation of the foreare basin previously developed in a setting of oceanic subduction. Sediments of the forearc basin are involved in the growth of a new thrust ridge backthrusted against the basement slope of the volcanic arc edifice. Sediments coming from the growing orogenic wedge are trapped in the trough developed between its backpart and the topographic high of the new rising ridge. A syn-collisional orogenic basin develops which structural evolution characterizes the progressive shortening of the forearc domain. Most of the deformation and tectonic events recorded offshore or onland in the complex area south of Taiwan can be explained using results of our specific modeling which well describe the tectonic processes associated with continental subduction under a volcanic are.
ISSN: 0040-1951

hal-00420080
https://hal.archives-ouvertes.fr/hal-00420080
DOI : 10.1016/j.tecto.2007.11.016

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The Middle Atlas is a region where xenolith-bearing volcanism roughly coincides with the maximum of lithospheric thinning beneath continental Morocco. It is therefore a key area to study the mechanisms of lithospheric thinning and constrain the component of mantle buoyancy that is required to explain the Moroccan topography. Samples from the two main xenolith localities, the Bou Ibalghatene and Tafraoute maars, have been investigated for their mineralogy, microstructures, crystallographic preferred orientation, and whole-rock and mineral compositions. While Bou Ibalghatene belongs to the main Middle Atlas volcanic field, in the ‘tabular’ Middle Atlas, Tafraoute is situated about 45 km away, on the North Middle Atlas Fault that separates the ‘folded’ Middle Atlas, to the South-East, from the ‘tabular’ Middle Atlas, to the North-West. Both xenolith suites record infiltration of sub-lithospheric melts that are akin to the Middle Atlas volcanism but were differentiated to variable degrees as a result of interactions with lithospheric mantle. However, while the Bou Ibalghatene mantle was densely traversed by high melt fractions, mostly focused in melt conduits, the Tafraoute suite records heterogeneous infiltration of smaller melt fractions that migrated diffusively, by intergranular porous flow. As a consequence the lithospheric mantle beneath Bou Ibalghaten was strongly modified by melt–rock interactions in the Cenozoic whereas the Tafraoute mantle preserves the record of extensional lithospheric thinning, most likely related to Mesozoic rifting. The two xenolith suites illustrate distinct mechanisms of lithospheric thinning: extensional thinning in Tafraoute, where hydrous incongruent melting triggered by decompression probably played a key role in favouring strain localisation, vs. thermal erosion in Bou Ibalghatene, favoured and guided by a dense network of melt conduits. Our results lend support to the suggestion that lithospheric thinning beneath the Atlas mountains results from the combination of different mechanisms and occurred in a piecewise fashion at a short wavelength scale.
ISSN: 0040-1951

hal-01171756
https://hal.archives-ouvertes.fr/hal-01171756
DOI : 10.1016/j.tecto.2014.11.020

Éditeur(s) : HAL CCSD
Résumé : Among erosion processes, river incision is classicaly described as a key process controlling erosion of landscapes. Incision efficiency is mainly influenced by climate and erodibility. This latter is not only dependent on the nature of the bedrock, but also on its past deformation, which affects its rheological effective properties, such as fracture density. The main objectives of this thesis are: (1) to better constrain the relationship between effective properties and erodibility, and (2) to quantify the influence of erodibility and erosion on both the temporal and spatial building or decay of the topography. Several numerical tools are developed. A 1D formalism of landscape evolution is introduced, including river incision with stochastic distribution of water discharge and hillslope landsliding. A new remeshing algorithm called Surface Lagrangian Remeshing (SLR) is developed as a complement to remeshing algorithms dealing with internal elements. It allows one to take into account long-term erosion into 2D Lagrangian numerical codes based on triangular finite elements. Then the potentiality of measuring erodibility in-situ using a Schmidt hammer (R) is assessed for the active orogen of Taiwan, the diagenetic Annot sandstones and St Clement fault zone. Results suggest a strong control of R by effective properties. A linear model based on effective medium theory is applied to a fault zone with an unmacthed resolution (750 measures, 25 measures per square meter). The model successfully correlates R to fracture density. These results demonstrate that effective elasticity as well as erodibility are sensitive to the density and type of fractures. Finally I focus on the erosional and rheological conditions that allows reproducing post-orogenic evolution of mountain belts. A model coupling surface erosion and regional isostatic uplift is consistent with observations. The topographic decay and decrease of the ratio of surface elevation over crustal root thickness is at first order controlled by the initial geometry of the mountain belt and erosion efficiency. This new model highlights the control ofclimate and erodibility on the topographic decay and of lithospheric rheology on the perseverance of crustal roots.
Parmi les processus d'érosion, l'incision des rivières est classiquement décrit comme un processus clé contrôlant l'érosion des paysages. L'efficacité de l'incision est principalement influencée par le climat et par l'érodabilité. Ce dernier paramètre ne dépend pas seulement de la nature du substratum rocheux, mais aussi de sa déformation passée qui affecte ses propriétés rhéologiques équivalentes. Les principaux objectifs de cette thèse sont: (1) de mieux contraindre les relations entre propriétés équivalentes et érodabilité, et (2) de quantifier l'influence de l'érosion et de l'érodabilité sur la formation ou la décadence, spatiale et temporelle, de la topographie. Plusieurs outils numériques sont développés. Un formalisme 1D d'évolution des paysages est proposé, prenant en compte simultanément l'incision des rivières avec une distribution stochastique des débits en eau et l'érosion des versants par glissements de terrain. Un nouvel algorithme de remaillage appelé Surface Lagrangian Remeshing (SLR) est développé. Il permet de prendre en compte l'érosion à long terme dans les codes numériques 2D Lagrangiens basés sur des éléments finis triangulaires. Ensuite, la possibilité de mesurer in-situ l'érodabilité avec un marteau de Schmidt (R) est évaluée pour: l'orogène actif de Taiwan, les grès diagénétiques d'Annot et la zone de faille de St Clément. Les résultats suggèrent un fort contrôle de R par les propriétés équivalentes des roches testées. Un modèle linéaire, basé sur la théorie des milieux équivalents, est appliqué à une zone de faille avec une résolution inégalée (750 mesures, 25 mesures par mètre carré). Le modèle permet de corréler avec succès la densité de fracture et R. Ces résultats démontrent empiriquement que l'élasticité équivalente ainsi que l'érodabilité sont sensibles à la densité et à la nature des fractures. Enfin j'étudie les conditions d'érosion et de rhéologie qui permettent de reproduire l'évolution des chaînes de montagnes post-orogéniques. Un modèle couplant érosion en surface et soulèvement isostatique régional est compatible avec les observations. Les taux de décroissance topographique et de diminution du rapport de l'élévation de surface sur l'épaisseur de racine crustale sont contrôlés au premier ordre par la géométrie initiale de la chaîne de montagne et par l'efficacité de l'érosion. Ce nouveau modèle met en évidence le contrôle du climat et de l'érodabilité sur la décroissance topographique et de la rhéologie lithosphérique sur la persévérance des racines crustales.
https://tel.archives-ouvertes.fr/tel-00602341

tel-00602341
https://tel.archives-ouvertes.fr/tel-00602341
https://tel.archives-ouvertes.fr/tel-00602341/document
https://tel.archives-ouvertes.fr/tel-00602341/file/thesephilippesteer.pdf

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : Approximately 4 yr of campaign and continuous Global Positioning System (GPS) measurements across the Dead Sea fault system (DSFS) in Lebanon provide direct measurements of interseismic strain accumulation along a 200-km-long restraining bend in this continental transform fault. Late Cenozoic transpression within this restraining bend has maintained more than 3000 m of topography in the Mount Lebanon and Anti-Lebanon ranges. The GPS velocity field indicates 4-5 mm yr(-1) of relative plate motion is transferred through the restraining bend to the northern continuation of the DSFS in northwestern Syria. Near-field GPS velocities are generally parallel to the major, left-lateral strike-slip faults, suggesting that much of the expected convergence across the restraining bend is likely accommodated by different structures beyond the aperture of the GPS network (e.g. offshore Lebanon and, possibly, the Palmyride fold belt in SW Syria). Hence, these geodetic results suggest a partitioning of crustal deformation involving strike-slip displacements in the interior of the restraining bend, and crustal shortening in the outer part of the restraining bend. Within the uncertainties, the GPS-based rates of fault slip compare well with Holocene-averaged estimates of slip along the two principal strike-slip faults: the Yammouneh and Serghaya faults. Of these two faults, more slip occurs on the Yammouneh fault, which constitutes the primary plate boundary structure between the Arabia and Sinai plates. Hence, the Yammouneh fault is the structural linkage that transfers slip to the northern part of the transform in northwestern Syria. From the perspective of the regional earthquake hazard, the Yammouneh fault is presently locked and accumulating interseismic strain.
ISSN: 0956-540X

hal-00406620
https://hal.archives-ouvertes.fr/hal-00406620
DOI : 10.1111/j.1365-246X.2006.03328.x

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Lateral variations along the Himalayan arc are suggested by an increasing number of studies and carry important information about the orogen’s segmentation. Here we compile the hitherto most complete land gravity dataset in the region which enables the currently highest resolution plausible analysis. To study lateral variations in collisional structure we compute arc-parallel gravity anomalies (APaGA) by subtracting the average arc-perpendicular profile from our dataset; we compute likewise for topography (APaTA). We find no direct correlation between APaGA, APaTA and background seismicity, as suggested in oceanic subduction context. In the Himalayas APaTA mainly reflect relief and erosional effects, whereas APaGA reflect the deep structure of the orogen with clear lateral boundaries. Four segments are outlined and have disparate flexural geometry: NE India, Bhutan, Nepal & India until Dehradun, and NW India. The segment boundaries in the India plate are related to inherited structures, and the boundaries of the Shillong block are highlighted by seismic activity. We find that large earthquakes of the past millennium do not propagate across the segment boundaries defined by APaGA, therefore these seem to set limits for potential rupture of megathrust earthquakes.
ISSN: 2045-2322

hal-01420404
https://hal.archives-ouvertes.fr/hal-01420404
https://hal.archives-ouvertes.fr/hal-01420404/document
https://hal.archives-ouvertes.fr/hal-01420404/file/hetenyi2016.pdf
DOI : 10.1038/srep33866

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Lithospheric-scale faults related to oblique subduction are responsible for some of the most hazardous earthquakes reported worldwide. The mega-thrust in the Sunda sector of the Sumatran oblique subduction has been intensively studied, especially after the infamous 2004 Mw 9.1 earthquake, but its onshore kinematic complement within the Sumatran subduction, the transform Sumatran Fault System, has received considerably less attention. In this paper, we apply a combination of analysis of Digital Elevation Models (ASTER GDEM) and field evidence to resolve the kinematics of the leading edge of deformation of the northern sector of the Sumatran Fault System. To this end, we mapped the northernmost tip of Sumatra, including the islands to the northwest, between 4.5°N and 6°N. Here, major topographic highs are related to different faults. Using field evidence and our GDEM structural mapping, we can show that in the area where the fault bifurcates into two fault strands, two independent kinematic regimes evolve, both consistent with the large-scale framework of the Sumatran Fault System. Whereas the eastern branch is a classic Riedel system, the western branch features a fold-and-thrust belt. The latter contractional feature accommodated significant amounts (c. 20%) of shortening of the system in the study area. Our field observations of the tip of the NSFS match a strain pattern with a western contractional domain (Pulau Weh thrust splay) and an eastern extensional domain (Pulau Aceh Riedel system), which are together characteristic of the tip of a propagating strike-slip fault, from a mechanical viewpoint. For the first time, we describe the strain partitioning resulting from the propagation of the NSFS in Sumatra mainland. Our study helps understanding complex kinematics of an evolving strike-slip system, and stresses the importance of field studies in addition to remote sensing and geophysical studies.
ISSN: 0040-1951

hal-01467196
https://hal.archives-ouvertes.fr/hal-01467196
DOI : 10.1016/j.tecto.2016.04.050