Samovar: a thermomechanical code for modeling of geodynamic processes in the lithosphere—application to basin evolution     

Yuriy Elesin  Taras Gerya  Irina M. Artemieva  Hans Thybo 《Arabian Journal of Geosciences》2010,3(4):477-497

We present a new 2D finite difference code, Samovar, for high-resolution numerical modeling of complex geodynamic processes. Examples are collision of lithospheric plates (including mountain building and subduction) and lithosphere extension (including formation of sedimentary basins, regions of extended crust, and rift zones). The code models deformation of the lithosphere with viscoelastoplastic rheology, including erosion/sedimentation processes and formation of shear zones in areas of high stresses. It also models steady-state and transient conductive and advective thermal processes including partial melting and magma transport in the lithosphere. The thermal and mechanical parts of the code are tested for a series of physical problems with analytical solutions. We apply the code to geodynamic modeling by examining numerically the processes of lithosphere extension and basin formation. The results are directly applicable to the Basin and Range province, western USA, and demonstrate the roles of crust–mantle coupling, preexisting weakness zones, and erosion rate on the evolutionary trends of extending continental regions. Modeling of basin evolution indicates a critical role of syn-rift sedimentation on the basin depth and a governing role of Peierls deformation in cold lithospheric mantle. While the former may increase basin depth by 50%, the latter limits the depth of rift basins by preventing faulting in the subcrustal lithosphere.  相似文献   

The dependence of transport properties ofin situ rocks on pore fluid composition and temperature     

I. M. Artemieva 《Surveys in Geophysics》1996,17(3):289-306

Fluids saturating cracked rocks within the crust can vary widely in composition and physical properties, which depend greatly on pressure and temperature. External non-hydrostatic stress applied to a cracked medium may result in a significant change of crack volume (and hence, for the undrained regime, pore-fluid pressure) due to the processes of crack closure (opening), and thus lead to a drastic change of the overall physical parameters of a rock. The purpose of the study is to estimate theoretically, using the effective-medium theory, the macroscopic seismic and transport parameters (such as permeability) of cracked rocks (granites) saturated with hydrocarbon gases, oils, brines and water. Variations of crack geometry and fluid parameters in the closed system (at constant fluid mass) under uniaxial compression are considered as well. The results show that composition of a saturating fluid as well as fluid temperature greatly influence the effective permeability and shear velocities of a rock mass, while thermal conductivity is not so sensitive to variations of fluid parameters.  相似文献   

Analytical extension of lunar libration tables     

Natasha Petrova 《Earth, Moon, and Planets》1996,73(1):71-99

Tables of lunar physical libration defining the analytical dependence upon the parameters of the lunar gravitational field are presented. The tables are obtained on the framework of the main problem in lunar libration by integration of the Hamilton equations reduced to the harmonic oscillator equations.The variables of physical libration have been obtained in the form of Poisson series. The distinguishing feature of the tables is that these series are the analytical extension of semianalytical solution computed for a number of dynamical parameters LURE2.A comparison with the Eckhardt's solution is briefly presented. The previously revealed disagreement of the mean inclination of lunar equator to ecliptic with that in Eckhardt's solution 500 has been maintained.  相似文献   

Cenozoic uplift and subsidence in the North Atlantic region: Geological evidence revisited     

I. Anell  H. Thybo  I.M. Artemieva   《Tectonophysics》2009,474(1-2):78

The topographic evolution of the “passive” margins of the North Atlantic during the last 65 Myr is the subject of extensive debate due to inherent limitations of the geological, geomorphological and geophysical methods used for studies of uplift and subsidence. We have compiled a database of sign, time and amplitude (where possible) of topographic changes in the North Atlantic region during the Cenozoic (65–0 Ma). Our compilation is based on published results from reflection seismic studies, AFT (apatite fission track) studies, VR (vitrinite reflectance) trends, maximum burial, sediment supply studies, mass balance calculations and extrapolation of seismic profiles to onshore geomorphological features. The integration of about 200 published results reveal a clear pattern of topographic changes in the North Atlantic region during the Cenozoic: (1) The first major phase of Cenozoic regional uplift occurred in the late Palaeocene–early Eocene (ca 60–50 Ma), probably related to the break-up of the North Atlantic between Europe and Greenland, as indicated by the northward propagation of uplift. It was preceded by middle Palaeocene uplift and over-deepening of some basins of the North Sea and the surrounding areas. (2) A regional increase in subsidence in the offshore marginal areas of Norway, the northern North Sea, the northern British Isles and west Greenland took place in the Eocene (ca 57–35 Ma). (3) The Oligocene and Miocene (35–5 Ma) were characterized by regional tectonic quiescence, with only localised uplift, probably related to changes in plate dynamics. (4) The second major phase of regional uplift that affected all marginal areas of the North Atlantic occurred in the Plio-Pleistocene (5–0 Ma). Its amplitude was enhanced by erosion-driven glacio-isostatic compensation. Despite inconclusive evidence, this phase is likely to be ongoing at present.  相似文献   

Crater ejecta: Markers of impact catastrophes   总被引：1，自引：0，他引：1  

V. V. Shuvalov  N. A. Artemieva  M. Yu. Kuz’micheva  T. V. Losseva  V. V. Svettsov  V. M. Khazins 《Izvestiya Physics of the Solid Earth》2012,48(3):241-255

The role of impact crater ejecta in the evolution of the Earth and Solar System planets is considered. Using the methods of numerical modeling, the accretion and erosion of planets, the redistribution of planetary material due to impacts of large cosmic bodies and related geospheric interactions, the asymmetrical deposition of ejecta around the crater rim, and the possibility of nonballistic transportation of ejecta are analyzed. The influence of impact events on the Earth’s envelopes is compared with the effects of volcanic eruptions.  相似文献   

Geophysical and Hydrologic Studies of Lake Seepage Variability          下载免费PDF全文

Laura Toran  Jonathan Nyquist  Donald Rosenberry  Michael Gagliano  Natasha Mitchell  James Mikochik 《Ground water》2015,53(6):841-850

Variations in lake seepage were studied along a 130 m shoreline of Mirror Lake NH. Seepage was downward from the lake to groundwater; rates measured from 28 seepage meters varied from 0 to ?282 cm/d. Causes of this variation were investigated using electrical resistivity surveys and lakebed sediment characterization. Two‐dimensional (2D) resistivity surveys showed a transition in lakebed sediments from outwash to till that correlated with high‐ and low‐seepage zones, respectively. However, the 2D survey was not able to predict smaller scale variations within these facies. In the outwash, fast seepage was associated with permeability variations in a thin (2 cm) layer of sediments at the top of the lakebed. In the till, where seepage was slower than that in the outwash, a three‐dimensional resistivity survey mapped a point of high seepage associated with heterogeneity (lower resistivity and likely higher permeability). Points of focused flow across the sediment–water interface are difficult to detect and can transmit a large percentage of total exchange. Using a series of electrical resistivity geophysical methods in combination with hydrologic data to locate heterogeneities that affect seepage rates can help guide seepage meter placement. Improving our understanding of the causes and types of heterogeneity in lake seepage will provide better data for lake budgets and prediction of mass transfer of solutes or contaminants between lakes and groundwater.  相似文献   

An Empirical Evaluation of the Influence of Ethanol on Natural Attenuation of Gasoline Constituents          下载免费PDF全文

Kirk O'Reilly  Catalina Espino Devine  Natasha Sihota  Katharine North 《Ground Water Monitoring & Remediation》2016,36(3):62-72

Since the 1990s, questions have arisen as to whether the release of ethanol‐blended fuel will inhibit natural attenuation of other gasoline constituents in groundwater. This study evaluated the hypothesis that ethanol affects hydrocarbon attenuation and whether the use of ethanol‐blended fuel alters the applicability of monitored natural attenuation (MNA) as an approach for managing risks at fuel‐release sites. Groundwater data from California's GeoTracker database were used to compare attenuation of benzene, toluene, methyl tert‐butyl ether (MTBE), and tert‐butyl alcohol (TBA) at sites with and without detections of ethanol. Excel‐based tools were developed to conduct attenuation evaluations on thousands of wells simultaneously. Ethanol was detected at least once in 4.5% of the wells and 0.6% of the samples of which it was analyzed. The distribution of Mann‐Kendall concentration trend analysis results and first‐order attenuation rates were essentially the same at sites with or without ethanol detections. Median plume lengths were shorter at sites where ethanol had not been detected compared to sites where ethanol was detected (36 vs. 43 m for benzene; 36 vs. 42 m for toluene; 43 vs. 52 m for MTBE; and 44 vs. 59 m for TBA). However, the distribution of plume lengths was similar irrespective of ethanol concentrations, suggesting other factors may influence plume elongation. Finally, while anaerobic ethanol degradation can result in methane generation, the distributions of methane concentrations were the same at sites with and without ethanol detections. These results suggest that the use of ethanol‐blended fuel should not limit the application of MNA at most biodegrading fuel‐release sites.  相似文献   

Overcoming cross-scale challenges to climate change adaptation for local government: a focus on Australia     

Pierre Mukheibir  Natasha Kuruppu  Anna Gero  Jade Herriman 《Climatic change》2013,121(2):271-283

This paper aims to identify key cross-scale challenges to planned adaptation within the context of local government in Australia, and suggest enabling actions to overcome such challenges. Many of the impacts of climate change and variability have or will be experienced at the local level. Local governments are embedded in a larger governance context that has the potential to limit the effectiveness of planned adaptation initiatives on the ground. This study argues that research on constraints and barriers to adaptation must place greater attention to understanding the broader multi-governance system and cross-scale constraints that shape adaptation at the local government scale. The study identified seven key enabling actions for overcoming cross-scale challenges faced by local governments in Australia when undertaking climate change adaptation planning and implementation. A central conclusion of this study is that a cooperative and collaborative approach is needed where joint recognition of the scale of the issue and its inherent cross-scale complexities are realised. Many of the barriers or constraints to adaptation planning are interlinked, requiring a whole government approach to adaptation planning. The research suggests a stronger role at the state and national level is required for adaptation to be facilitated and supported at the local level.  相似文献   

ICT-driven projects for land governance in Kenya: disruption and e-government frameworks     

Christopher Huggins  Natasha Frosina 《GeoJournal》2017,82(4):643-663

Critical academic research has yet to comprehensively identify conceptual linkages and tensions between information communication technologies (ICTs) and land governance projects. In order to make a contribution to these complex research fields, this article examines three Kenyan projects to illustrate different aspects of competing theoretical frameworks for ICT-based land rights projects. The projects documented land and property in the informal settlements of Kibera and Mathare in Nairobi, and in the rural community of Lari in Kiambu County. Drawing particularly on conceptual frameworks that emphasize the ‘disruptive’ potentials of ICTs, and frameworks based on e-government models, the article argues that these projects include both disruptive aspects, which work through applying pressure on the state, and more ‘integrative’ approaches which seek to build state capacity. The projects also rely on multiple stakeholders, and cannot be easily categorized within simple narratives of crowdsourcing, for example. Instead the realities are more complex and ‘success’ is difficult to assess, and potential uses of such projects are open and multiple.  相似文献   

Seismic efficiency of meteor airbursts     

Svetsov  V. V.  Artemieva  N. A.  Shuvalov  V. V. 《Doklady Earth Sciences》2017,475(2):935-938

We present the results of numerical simulation for impacts of relatively small asteroids and ice bodies of 30–100 m in size, decelerated in the atmosphere and exploding before they reach the surface, but still producing seismic effects due to the impact wave reaching the surface. The calculated magnitudes fall within the range of 4 to 6, and average seismic efficiency of these events is 2.5 × 10^–5. The results obtained allow the seismic hazard from impacts of cosmic bodies to be estimated.

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