Random partitioning and adaptive filters for multiple-point stochastic simulation     

Mansoureh?SharifzadehlariEmail authorView author&#;s OrcID profile  Nader?Fathianpour  Philippe?Renard  Rassoul?Amirfattahi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(5):1375-1396

Multiple-point geostatistical simulation is used to simulate the spatial structures of geological phenomena. In contrast to conventional two-point variogram based geostatistical methods, the multiple-point approach is capable of simulating complex spatial patterns, shapes, and structures normally observed in geological media. A commonly used pattern based multiple-point geostatistical simulation algorithms is called FILTERSIM. In the conventional FILTERSIM algorithm, the patterns identified in training images are transformed into filter score space using fixed filters that are neither dependent on the training images nor on the characteristics of the patterns extracted from them. In this paper, we introduce two new methods, one for geostatistical simulation and another for conditioning the results. At first, new filters are designed using principal component analysis in such a way to include most structural information specific to the governing training images resulting in the selection of closer patterns in the filter score space. We then propose to combine adaptive filters with an overlap strategy along a raster path and an efficient conditioning method to develop an algorithm for reservoir simulation with high accuracy and continuity. We also combine image quilting with this algorithm to improve connectivity a lot. The proposed method, which we call random partitioning with adaptive filters simulation method, can be used both for continuous and discrete variables. The results of the proposed method show a significant improvement in recovering the expected shapes and structural continuity in the final simulated realizations as compared to those of conventional FILTERSIM algorithm and the algorithm is more than ten times faster than FILTERSIM because of using raster path and using small overlap specially when we use image quilting.  相似文献   

Methane Occurrences in Aquifers Overlying the Barnett Shale Play with a Focus on Parker County,Texas          下载免费PDF全文

Jean‐Philippe Nicot  Patrick Mickler  Toti Larson  M. Clara Castro  Roxana Darvari  Kristine Uhlman  Ruth Costley 《Ground water》2017,55(4):469-481

Clusters of elevated methane concentrations in aquifers overlying the Barnett Shale play have been the focus of recent national attention as they relate to impacts of hydraulic fracturing. The objective of this study was to assess the spatial extent of high dissolved methane previously observed on the western edge of the play (Parker County) and to evaluate its most likely source. A total of 509 well water samples from 12 counties (14,500 km²) were analyzed for methane, major ions, and carbon isotopes. Most samples were collected from the regional Trinity Aquifer and show only low levels of dissolved methane (85% of 457 unique locations <0.1 mg/L). Methane, when present is primarily thermogenic (δ¹³C 10th and 90th percentiles of ?57.54 and ?39.00‰ and C1/C2+C3 ratio 10th, 50th, and 90th percentiles of 5, 15, and 42). High methane concentrations (>20 mg/L) are limited to a few spatial clusters. The Parker County cluster area includes historical vertical oil and gas wells producing from relatively shallow formations and recent horizontal wells producing from the Barnett Shale (depth of ～1500 m). Lack of correlation with distance to Barnett Shale horizontal wells, with distance to conventional wells, and with well density suggests a natural origin of the dissolved methane. Known commercial very shallow gas accumulations (<200 m in places) and historical instances of water wells reaching gas pockets point to the underlying Strawn Group of Paleozoic age as the main natural source of the dissolved gas.  相似文献   

The fourth Arab Impact Cratering and Astrogeology Conference (AICAC IV), April 9–12, 2017, Algiers (Algeria)          下载免费PDF全文

D. Belhaï  H. Chennaoui‐Aoudjehane  D. Baratoux  L. Ferrière  A. Lamali  R. Sahoui  P. Lambert  A. Ayadi 《Meteoritics & planetary science》2017,52(9):2067-2071

We present a report about the fourth Arab Impact Cratering and Astrogeology Conference (AICAC IV) that took place in Algiers at the USTHB (Université des Sciences et Technologie Houari Boumedienne, Algiers, Algeria) in the presence of the presidents of the USTHB and Boumerdès Universities, the Director of CRAAG (Centre de Recherche en Astronomie, Astrophysique et Géophysique), and the General Director of the National Administration for Scientific Research (NASR/DGRSDT). This series of conferences aims to promote research interest for impact cratering in the Arab world and beyond, including for instance in African countries. In spite of persistently restraining travel measures to Algeria, the fourth edition held in Algiers was marked by continuous international participation, with participants from seven different countries. This conference focused on presentations of scientific results in the research fields related to planetology, meteorites, and impact craters. In particular, the Algerian impact structures were under the spotlights during both oral and poster sessions. During this conference, the presence of freshly graduated Ph.D. students and new Ph.D. projects related to impact cratering or meteoritic science was a positive sign for the consolidation of research groups in this domain in the Arab world and Africa. Therefore, international cooperation or external support and funding are still needed to ensure the development of this scientific discipline in this part of the world.  相似文献   

The Stubenberg meteorite—An LL6 chondrite fragmental breccia recovered soon after precise prediction of the strewn field          下载免费PDF全文

Addi Bischoff  Jean‐Alix Barrat  Kerstin Bauer  Christoph Burkhardt  Henner Busemann  Samuel Ebert  Michael Gonsior  Janina Hakenmüller  Jakub Haloda  Dennis Harries  Dieter Heinlein  Harald Hiesinger  Rupert Hochleitner  Viktor Hoffmann  Melanie Kaliwoda  Matthias Laubenstein  Colin Maden  Matthias M. M. Meier  Andreas Morlok  Andreas Pack  Alexander Ruf  Philippe Schmitt‐Kopplin  Maria Schönbächler  Robert C. J. Steele  Pavel Spurný  Karl Wimmer 《Meteoritics & planetary science》2017,52(8):1683-1703

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Geological controls on BSR occurrences in the incipient arc-continent collision zone off southwest Taiwan     

Che-Chuan Lin  Andrew Tien-Shun Lin  Char-Shine Liu  Guan-Yu Chen  Wei-Zhi Liao  Philippe Schnurle 《Marine and Petroleum Geology》2009

Bottom simulating reflectors (BSRs) observed on seismic sections are often considered as indicators for the existence of free gas, delineating the base of the gas hydrate stability zone. Abundant BSRs seen on seismic sections acquired off the SW coast of Taiwan indicate the likely and prevalent existence of gas hydrates in the study area. This study aims to characterize the occurrence of BSRs off SW Taiwan and to understand their relationship to topography, tectonic activity, and possible migration paths of gas-bearing fluids in this area.  相似文献   

Is feeding behaviour related to glass eel propensity to migrate?     

Sarah Bureau du Colombier  Patrick Lambert  Agnès Bardonnet 《Estuarine, Coastal and Shelf Science》2008

Several studies have shown that eel diadromy is facultative and that migratory divergences may appear during glass eel estuarine migration. The origin of the differences in migratory behaviour among glass eels remains unclear but initial evidence supports the role of individual energetic and thyroidal status. Even if starvation is usually associated with glass eel migration, feeding does seem to occur in some glass eels. The aim of the present study was to investigate feeding behaviour and glass eel growth in relation to the propensity to migrate. Feeding rate and weight gain were higher in fish having a high propensity to migrate (M⁺ fish) than in fish having a low propensity to migrate (M⁻ fish) in fed glass eels, whereas no clear difference in the variation in body weight was observed among unfed fish (controls). M⁻ fish initially had lower percent dry weight than M⁺ fish, which suggests a link between appetite, propensity to migrate, and energy content. We discuss the role played by endocrine signals on these processes. In fish, thyroid hormones contribute to the control of growth and development. In addition, they play a role in flatfish and leptocephalus metamorphosis and appear to be involved in smolt and glass eel migratory behaviour. As such, they represent a good candidate which would promote the propensity to migrate as well as digestive system development. Their role in the hormonal control of food intake however remains vague.  相似文献   

Post‐Last Glacial Maximum glacier fluctuations in the southern Écrins massif (westernmost Alps): insights from 10Be cosmic ray exposure dating     

Felix Martin Hofmann  Helena Alexanderson  Philippe Schoeneich  Jordan R. Mertes  Laëtitia Lanni 《Boreas: An International Journal of Quaternary Research》2019,48(4):1019-1041

Only a few chronological constraints on Lateglacial and Early Holocene glacier variability in the westernmost Alps have hitherto been obtained. In this paper, moraines of two palaeoglaciers in the southern Écrins massif were mapped. The chronology of the stabilization of selected moraines was established through the use of ¹⁰Be cosmic ray exposure (CRE) dating. The equilibrium line altitude (ELA) during moraine deposition was reconstructed assuming an accumulation area ratio (AAR) of 0.67. Ten pre‐Little Ice Age (LIA) ice‐marginal positions of the Rougnoux palaeoglacier were identified and seven of these have been dated. The ¹⁰Be CRE age of a boulder on the lowermost sampled moraine indicates that the landform may have been first formed during a period of stable glaciers at around 16.2±1.7 ka (kiloyears before AD 2017) or that the sampled boulder experienced pre‐exposure to secondary cosmic radiation. The moraine was re‐occupied or, alternatively, shaped somewhat before 12.2±0.6 ka when the ELA was lowered by 230 m relative to the LIA ELA. At least six periods of stable ice margins occurred thereafter when the ELA was 220–160 m lower than during the LIA. The innermost dated moraine stabilized at or before 10.9±0.7 ka. Three ¹⁰Be CRE ages from a moraine of the Prelles palaeoglacier indicate a period of stationary ice margins at or before 10.9±0.6 ka when the ELA was lowered by 160 m with respect to the end of the LIA. The presented ¹⁰Be CRE ages are in good agreement with those of moraines that have been attributed to the Egesen stadial. Assuming unchanged precipitation, summer temperature in the southern Écrins massif at ~12 ka must have been at least 2 °C lower relative to the LIA.  相似文献   

Compositional tomography of a gold‐bearing sample by Laser‐induced breakdown spectroscopy     

Flix Gervais  Kheireddine Rifai  Philippe Plamondon  Lütfü zcan  Franois Doucet  Franois Vidal 《地学学报》2019,31(5):479-484

This contribution presents the first results of compositional tomography of a geological sample. The volume render of 6 × 8 × 1 mm³ was constructed by assembling 63 compositional maps acquired in 21 min (19.5 s/layer) by laser‐induced breakdown spectroscopy (LIBS), which determines the chemical composition of the analysed spot from the light emitted by a plasma produced by the laser. This technique is, therefore, able to directly reveal the 3D distribution of chemical elements in a sample. As an example, the spatial distribution and 3D geometry of visible gold in an ultramafic schist are presented. Inasmuch as this newly developed portable LIBS instrument is able to the rapidly characterize the 3D geometry of any geological materials, it has a high potential to be useful for the mining industry and for a wide range of geosciences, such as structural geology, petrology, sedimentology and economic geology.  相似文献   

Impact of Hurricane Irene and Tropical Storm Lee on riparian zone hydrology and biogeochemistry          下载免费PDF全文

Philippe Vidon  Sara Marchese  Stephen Rook 《水文研究》2017,31(2):476-488

Although riparian zones are well known to reduce nitrogen (N) and phosphorus (P) runoff to streams, they also have the potential to affect greenhouse gas (CO₂, N₂O, and CH₄) fluxes to the atmosphere. Following large storms, soil biogeochemical conditions often become more reduced, especially in oxbow depressions and side channels, which can lead to hot moments of greenhouse gas production. Here, we investigate the impact of the remnants of Hurricane Irene and Tropical Storm Lee on riparian zone hydrology (water table: WT), and biogeochemistry (oxidation‐reduction potential [ORP], dissolved oxygen [DO], NO₃^?, PO₄^3?, CO₂, N₂O, CH₄). Results indicate that large storms have the potential to reset WT levels for weeks to months. Overbank flooding at our site following Irene and Lee led to the infiltration of well‐oxygenated water at depth (higher DO and ORP) while promoting the development of anoxic conditions within soil aggregates near the soil surface (increased N₂O and CH₄ fluxes). A short‐term increase in CO₂ emission was observed following Irene at our site where aerobic respiration was water‐limited. Over a 2‐year period, an oxbow depression exhibited higher WT, higher N₂O and CH₄ fluxes (hot moment), higher CO₂ fluxes (seasonal), and lower NO₃^? concentrations (seasonal) than the rest of the riparian zone. However, neither Irene, nor Lee, nor the oxbow depression significantly impacted PO₄^3?. Dissolved organic carbon, ORP, and DO data illustrate the time‐lag (>20 years) between the creation of an oxbow depression and the development of reducing conditions despite clear differences in riparian zone and oxbow WT dynamics.  相似文献   

Quaternary thermokarst and thermal erosion features in northern France: origin and palaeoenvironments     

Brigitte Van Vliet‐Lanoë  Jacques Brulhet  Philippe Combes  Cédric Duvail  Frédéric Ego  Stéphane Baize  Isabelle Cojan 《Boreas: An International Journal of Quaternary Research》2017,46(3):442-461

A thermokarst is a collapse feature resulting from the thawing of ice‐rich permafrost or of massive ice of various origins. Little attention has been paid to the sedimentary fabric resulting from this type of collapse, except for glaciotectonic features. In western Europe, two palaeo‐forms are commonly studied: lithalsas and ice‐wedge casts. Collapsed pingos are much rarer. Very few papers have compiled present‐day and fossil data. Here, field data collected from quarries in the eastern Paris Basin were analysed, providing useful records of thermokarst collapses in alluvial calcareous silts, sands, and gravels. These forms have a circular shape when viewed on satellite images. Permafrost is attested regionally by the recurrent occurrence of meter‐sized pattern grounds at the surface of the chalk and of ice‐wedge casts. Traces of segregation and reticulate ice are common. These features are primarily connected to a major interstadial, c. 150 ka BP, orbitally forced and commonly associated with a major glacial retreat. They occur both in drained and waterlogged situations, resulting in a specific pattern of deformation. They are controlled by the brittle and plastic behaviour of sediments and resemble passive glaciotectonism. Normal and reverse faults, with the offset decreasing downward, are common, and those with local shear are reported. Lithalsas, seasonal frost blisters, spring frost blisters and perhaps pingos seem to have formed. Most of these deformations correspond to thermokarst sinkholes bordered by gravitational collapse faults. The offset of these faults increases towards the surface, and the faults have been recurrently confused with neotectonism triggered by palaeo‐earthquakes. However, there are no faults beneath the observed deformation features, and the region lacks recorded seismic activity over the last century. Our data may be helpful in interpreting similar structures elsewhere.  相似文献