For more than 40 years, Earth observation satellites have been regularly providing images of glaciers that can be used to derive surface displacement fields and study their dynamics. In the context ...of global warming, the analysis of displacement field time series (DFTS) can provide useful information. Efficient data mining techniques are, thus, required to extract meaningful displacement evolutions from such large and complex datasets. In this paper, a pattern-based data mining approach, which handles confidence measures, is proposed to analyze DFTS. In order to focus on the most reliable measurements, a displacement evolution reliability measure is defined. It is aimed at assessing the quality of each evolution and pruning the search space. Experiments on two different DFTS (annual displacement fields derived from optical data over Greenland ice sheet and 11-day displacement fields derived from synthetic aperture radar data over Alpine glaciers) show the potential of the proposed approach.
We study the controls on drainage development in tectonically active regions using a numerical tectonic surface processes model combining tectonic uplift caused by fault‐related folding with erosion ...by fluvial incision, hillslope diffusion, and landsliding. Our model shows the fundamental control exerted by the dip of the detachment underlying the folds on drainage evolution. When the detachment is horizontal, the relative rates of tectonic uplift and fluvial incision control the evolution. For a nonzero dip, in contrast, the lateral displacement gradient associated with fold propagation sets up a lateral slope behind the active structure, which deflects the stream network. We also demonstrate the importance of landsliding for the attainment of realistic and steady state topography. In contrast, discontinuous tectonic movements do not appear to influence the system. We apply our model to the Dundwa fault‐related fold ridge (Siwalik, Nepal). We estimate a remarkably low mean propagation rate for different segments of the structure. This finding, together with the structure and morphology of the ridge, leads us to propose that the ridge developed by linkage of several component segments. The drainage evolution predicted when modeling this scenario compares favorably with field observations. Our models provide insights into the dynamics of fault‐related fold propagation: In particular, as a result of fault segment linkage, estimates of propagation rate of these structures may be strongly scale‐dependent, and the observed morphology and drainage patterns on fault‐related fold ridges may be controlled by fault geometry rather than by the relative rates of tectonics and surface processes.
The Medlicott-Wadia Thrust (MWT) is one of the major active out-of-sequence thrusts in the Himalaya. Studies on Quaternary terraces in its vicinity have been performed using sedimentological, ...geomorphic and geochronological methods. We focus on the Riasi zone, south of the Pir Panjal range, in the Jammu and Kashmir region of India. The sedimentary units of Quaternary landforms have been mapped as a function of their location with respect to the thrust faults, their relative chronology, and their lithology. Three aggrading sedimentary units, five thin units above strath surfaces at the footwall of the fault system, and seven thin units above strath surfaces at its hangingwall are identified. The terraces have been dated by combining Optically Stimulated Luminescence (OSL) on fine-grained deposits and cosmogenic-nuclide dating (10Be) on sandstone pebbles sampled along depth profiles throughout the alluvial units. Three major allostratigraphic units were defined with upper surface ages estimated at ~4, ~15, and 36±3ka; the two older allostratigraphic units are encased terraces at the hangingwall but superposed sedimentary units at the footwall. They are related to phases of elevation of the river level (respectively 30 and 60m) at ~36–38 and 14–15ka and to a phase of extensive lateral incision before ~4ka. These units present vertical offsets induced by the MWT of 50, 190, and 375m, respectively. By taking the aggradation/incision rates at the footwall of the MWT into account, we found that the uplift of the hangingwall remains uniform since 36ka, with a value of ~10mm/yr. Therefore, the aggradation/incision events observed in the Riasi area cannot be ascribed to variations in the tectonic rates and are most likely driven by climatic fluctuations. The high uplift rate is possibly local and related to the Chenab recess, which affects the Himalayan frontal structure. Our results indicate that the MWT is an active growth fault, and one of the main emergences of the active Indian/Asian plate boundary in Western Himalaya.
•The Main-Wadia Thrust is a very active out-of sequence thrust of Western Himalaya.•Three allostratigraphic units are dated at ~36, ~15, and 4ka by using 10Be and OSL methods.•The forming of the terraces is linked to climatic changes.•It found a constant vertical throw rate of 10.6±2mm/yr and an ~11mm/yr shortening since ~36ka.
Triple-A syndrome (MIM 231550; also known as Allgrove syndrome) is an autosomal recessive disorder characterized by adrenocorticotropin hormone (ACTH)-resistant adrenal insufficiency, achalasia of ...the oesophageal cardia and alacrima. Whereas several lines of evidence indicate that triple-A syndrome results from the abnormal development of the autonomic nervous system, late-onset progressive neurological symptoms (including cerebellar ataxia, peripheral neuropathy and mild dementia) suggest that the central nervous system may be involved in the disease as well. Using fine-mapping based on linkage disequilibrium in North African inbred families, we identified a short ancestral haplotype on chromosome 12q13 (<1 cM), sequenced a BAC contig encompassing the triple-A minimal region and identified a novel gene (AAAS) encoding a protein of 547 amino acids that is mutant in affected individuals. We found five homozygous truncating mutations in unrelated patients and ascribed the founder effect in North African families to a single splice-donor site mutation that occurred more than 2,400 years ago. The predicted product of AAAS, ALADIN (for alacrima-achalasia-adrenal insufficiency neurologic disorder), belongs to the WD-repeat family of regulatory proteins, indicating a new disease mechanism involved in triple-A syndrome. The expression of the gene in both neuroendocrine and cerebral structures points to a role in the normal development of the peripheral and central nervous systems.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
We studied a newly identified, multiple-kilometer-long rock slope failure in the Aiguilles Rouges massif (Chamonix valley, France). Owing to a high-resolution light detection and ranging (LiDAR) ...digital elevation model (DEM) and field work, we mapped morphostructures, including scarps, open fractures, and counterscarps. In some places, vertical offsets can reach tens of meters and crevasses can be meters wide. The evidence of gravitational activity (boulder displacements from analyses of archival satellite images) and the sharpness of the scarp outcrops together suggest very recent movements. These observations agree with ground displacement rates of a few millimeters per year estimated by interferometric synthetic aperture radar (InSAR) time series between 2014 and 2018.
We sampled two vertical profiles along the top scarps to define the chronology of the slope failure using beryllium-10 (10Be) surface exposure dating. Glacially polished surfaces cut by these gravitational scarps were also sampled to determine glacial retreat timing as well as to constrain the pre-exposure 10Be inheritance. In total, 11 samples were studied.
Our results highlight a significant time lag (approximately 15 ka) between the first evidence of nonglacial activity and the initiation of the slope failure that happened 1.3–2.5 ka ago, depending on the inheritance schemes. This suggests that the delayed opening of the crevasse is only one stage of a process that began when the valley was deepened and the glacial debuttressing is not the unique driving factor. This process of progressive failure of an excessively steep slope may continue, and the evolution of this slope failure may constitute a hazard for the upper part of the Chamonix valley.
Soft-sediment deformation structures have been analyzed at six sites of the Kathmandu valley. Microgranulometric study reveals that silty levels (60 to 80% silt) favor the development of ...soft-sediment deformation structures, while sandy levels (60 to 80% sand) are passively deformed. Nonetheless well sorted sand levels (more than 80% sand) generate over-fluid pressure during compaction if located beneath a silty cap, leading to fluidization and dike development. 3-D geometry of seismites indicates a very strong horizontal shearing during their development. Using a physical approach based on soil liquefaction during horizontal acceleration, we show that the fluidization zone progressively grows down-section during the shaking, but does not exactly begin at the surface. The comparison of bed-thickness and strength/depth evolution indicates three cases: i) no soft-sediment deformation occurs for thin (few centimeters) silty beds; ii) the thickness of soft-sediment deformation above sandy beds is controlled by the lithological contrast; iii) the thickness of soft-sediment deformation depends on the shaking intensity for very thick silty beds. These 3 cases are evidenced in the Kathmandu basin. We use the 30
cm-thick soft-sediment deformation level formed during the 1833 earthquake as a reference: the 1833 earthquake rupture zone extended very close to Kathmandu, inducing there MMI IX–X damages. A 90
cm-thick sediment deformation has therefore to be induced by an event greater than MMI X. From a compilation of paleo and historic seismology studies, it is found that the great (M
~
8.1) historical earthquakes are not characteristic of the greatest earthquakes of Himalaya; hence earthquakes greater than M
~
8.6 occurred. Kathmandu is located above one of the asperities that laterally limits the extent of mega-earthquake ruptures and two successive catastrophic events already affected Kathmandu, in 1255 located to the west of this asperity and in ~
1100 to the east.
► Soft-sediment deformation is controlled by the fluidization of silty levels. ► Shearing between planes parallel to the surface causes soft-sediment deformation. ► Pre-historic seismites are three times thicker than seismites linked to MMI X historic events. ► Kathmandu is at the transition between two segments of Himalaya. ► Two successive catastrophic earthquakes occurred during the 12th and 13th centuries.
In this paper, 3 years of surface displacement measurements obtained by space-borne synthetic aperture radar (SAR) observations are presented over the Argentière glacier in the Mont-Blanc massif, ...France. This temperate glacier is instrumented by a network of four Global Positioning System (GPS) stations used as ground truth. Thirty-eight pairs of descending and ascending high-resolution TerraSAR-X (TSX) acquisitions covering the study region are used to derive displacement fields at 11-day intervals in spring and summer 2009 and summer 2011. The combination of ascending and descending pairs acquired over the same period allows 3-D displacement fields to be inverted. Our SAR analysis quantifies displacement rates from 10 cm/day at the altitude of 2600 m to 30 cm/day at the altitude of 1800 m. Time series of SAR displacement results are compared with in situ GPS measurements of a continuous station set up at the altitude of 2441 m. Both data sources present displacement of the same order of magnitude with an average value of 20 cm/day in 3-D and show intra-seasonal variabilities, with fast accelerations over short time intervals.
A new generation of space-borne SAR sensors were launched in 2006-2007 with ALOS, TerraSAR-X, COSMO-Sky-Med and RadarSat-2 satellites. The data available in different bands (L, C and X bands), with ...High Resolution (HR) or multi-polarization modes offer new possibilities to monitor glacier displacement and surface evolution by SAR remote sensing. In this paper, the first results obtained with TerraSAR-X HR SAR image time series acquired over the temperate glaciers of the Chamonix Mont-Blanc test site are presented. This area involves well-known temperate glaciers which have been monitored and instrumented i.e. stakes for annual displacement/ablation, GPS for surface displacement and cavitometer for basal displacement, for more than 50 years. The potential of 11-day repeated X-band HR SAR data for Alpine glacier monitoring is investigated by a combined use of in situ measurements and multi-temporal images. Interpretations of HR images, analysis of interferometric pairs and performance assessments of target/texture tracking methods for glacier motion estimation are presented. The results obtained with four time series covering the Chamonix Mont-Blanc glaciers over one year show that the phase information is rarely preserved after 11 days on such glaciers, whereas the high resolution intensity information allows the main glacier features to be observed and displacement fields on the textured areas to be derived.
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