Fast 2.5D finite element simulations of borehole resistivity measurements     

Ángel Rodríguez-Rozas  David Pardo  Carlos Torres-Verdín 《Computational Geosciences》2018,22(5):1271-1281

We develop a rapid 2.5-dimensional (2.5D) finite element method for simulation of borehole resistivity measurements in transversely isotropic (TI) media. The method combines arbitrary high-order \(H^{1}\)- and \(\mathbf {H}\)(curl)-conforming spatial discretizations. It solves problems where material properties remain constant along one spatial direction, over which we consider a Fourier series expansion and each Fourier mode is solved independently. We propose a novel a priori method to construct quasi-optimal discretizations in physical and Fourier space. This construction is based on examining the analytical (fundamental) solution of the 2.5D formulation over multiple homogeneous spaces and assuming that some of its properties still hold for the 2.5D problem over a spatially heterogeneous formation. In addition, a simple parallelization scheme over multiple measurement positions provides efficient scalability. Our method yields accurate borehole logging simulations for realistic synthetic examples, delivering simulations of borehole resistivity measurements at a rate faster than 0.05 s per measurement location along the well trajectory on a 96-core computer.  相似文献   

Daily patterns of CO2 in the lower atmosphere of a rural site     

Isidro A. Pérez  M. Luisa Sánchez  M. Ángeles García  Nuria Pardo 《Theoretical and Applied Climatology》2015,122(1-2):195-205

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Dust pollution caused by an extreme Santa Ana wind event     

Álvarez  Christian A.  Carbajal  Noel  Pineda-Martínez  Luis F. 《Natural Hazards》2022,110(3):1427-1442

In arid and semiarid regions from the southwestern USA and vast areas of northwestern Mexico, Santa Ana wind events modify the environment with high temperatures, very low humidity, and dust storms representing a recurrent phenomenon that triggers asthma and other respiratory diseases. While research has emphasized Santa Ana wind effects on the USA side, northwestern Mexico has been less investigated. Numerical modeling of a severe dust storm in November 2018, applying the Weather Research and Forecasting model coupled with a chemistry module (WRF-Chem), revealed that erosion, transport, and dust storms extend along the peninsula and the Gulf of California. Santa Ana winds eroded large areas, transported desert conditions to urban zones, causing high dust concentrations and reducing the relative humidity below 10%, deteriorating climatic conditions favorable to wellness. In Tijuana, Mexicali, Ensenada, San Diego, and Los Angeles, PM10 and PM2.5 concentrations (particle matter with diameter below 10 µm and 2.5 µm) reached values over 2000 µg/m3 for PM10, with daily mean concentrations well above national standards, leading to poor air quality and representing a health threat even in short-term exposure. This Santa Ana event transported dust particles several hundreds of kilometers over urban areas, the Gulf of California, and the Pacific Ocean. Severe soil deterioration was simulated within the study area, reaching dust emissions above 700,000 t, including croplands from the northern part of Baja California and Sonora's coastal area.

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Mineralogical and geochemical implications of weathering rates in coastal dunes and beach sands close to a volcanic rock source in the western Gulf of Mexico,Mexico     

M. Mendieta-Lora  R.O. Mejía-Ledezma  J.J. Kasper-Zubillaga  E. Arellano-Torres  L.F. Álvarez Sánchez 《Chemie der Erde / Geochemistry》2018,78(3):323-339

Coastal dune (CD) and beach sand samples were mineralogically and chemically studied to assess the weathering rates in a coastal area surrounded by the Trans-Mexican Volcanic Belt (TMVB). The study area is a narrow coastal plain with sub-humid warm weather and vigorous coastal dynamics located in the Western Gulf of Mexico (WGM). Our results show that the grain size parameters remain homogeneous along nine CD and beach sites, probably due to the hydrodynamic mechanisms prevailing in the area, i.e. wind deflation, longshore currents, and waves. The minerals found in the CD and beach sands are enriched in recycled, highly corroded monocrystalline quartz (Qm), with loss of plagioclase (P) and olivine (ol), with ilmenite fractions (op) especially in the northern sites. The geochemical data show that the sands are controlled by the exhumation of the TMVB rocks composed of a high volcanic lithic content with lathwork, microlithic, and negligible vitric textures. These volcanic fractions are in agreement with the presence of lavas of calc alkaline, andesite, Na-alkaline lavas, and rhyolite tuffs derived from the TMVB. Significant Spearman Rank Correlations (SRCs) resulted from high silica, titanium, iron, magnesium, calcium, vanadium, chromium, cobalt, associated with the presence of Qm, ilmenite, clinopyroxene, shell fragments, and volcanic lithics. Monocrystalline quartz enrichments, compared to a quartz dilution effect (<Qm; < Qm) at the northern and southern beach sites, reflect the vigorous coastal dynamics. The presence of ilmenite lag deposits in the northern sites indicate that high energy hydrodynamic conditions prevail at the site. The rare earth element (REE) patterns support the mineralogical and compositional framework of the CD and beach sands as part of the TMVB exhumation. We used various chemical indices such as the Chemical Index of Alteration (CIA), the Chemical Index of Weathering (CIW), the Plagioclase Index of Alteration (PIA), and the Weathering Index of Plagioclase (WIP). The WIP values reflect the depletion of mobile elements such as Ca, Na, K, and enrichment of Qm at the northern beach sites, e.g. the Istirinchiá site. The CIA/WIP ratio of 2.13 indicates intermediate weathering under warm climatic conditions and recycling of CD and beach sands.  相似文献   

Efficient computational approaches to obtain periodic orbits in Hamiltonian systems: application to the motion of a lunar orbiter     

Ángeles Dena  Alberto Abad  Roberto Barrio 《Celestial Mechanics and Dynamical Astronomy》2016,124(1):51-71

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Neogene marine sediments and biota encapsulated between lava flows on Santa Maria Island (Azores,north-east Atlantic): An interplay between sedimentary,erosional and volcanic processes     

Alfred Uchman  Markes E. Johnson  Ricardo S. Ramalho  Rui Quartau  Björn Berning  Ana Hipólito  Carlos S. Melo  ANA C. Rebelo  Ricardo Cordeiro  Sérgio P. Ávila 《Sedimentology》2020,67(7):3595-3618

Sedimentary rocks are rarely preserved on reefless volcanic oceanic islands because their sediments are mostly exported from coastal areas towards the deep sea and such islands typically undergo subsidence. In contrast, the exceptional geological record of the uplifted Santa Maria Island (Azores) provides a unique opportunity to gain insight on such coastal systems. This study focuses on a locality at Ponta do Cedro (eastern Santa Maria Island), which features a series of marine fossiliferous sediments wedged between steep lava deltas. As demonstrated by local structure, these sediments correspond to clinoforms deposited on the steep submarine slope of an active volcanic island, implying transport from shallow waters to greater depths and subsequent colonization by benthic communities. Rapid volcanic progradation eventually sealed the deposits, allowing for their preservation and providing a rare snapshot of the ecology during those intervals, in addition to insights on sedimentary dynamics along submarine island slopes. This study reveals spatial relationships between wedges of sedimentary bodies encapsulated by lavas in the Ponta do Cedro section, and interprets depositional processes preserved in those strata based on sedimentological and palaeontological data. The dynamics of the environment are mostly related to relative sea-level changes, intense volcanic activity and regional uplift during the Neogene.  相似文献   

Testing Logselfsimilarity of Soil Particle Size Distribution: Simulation with Minimum Inputs     

Carlos García-Gutiérrez  Miguel Ángel Martín 《Pure and Applied Geophysics》2008,165(6):1117-1129

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Seismic activity prediction using computational intelligence techniques in northern Pakistan     

Khawaja M. Asim  Muhammad Awais  F. Martínez–Álvarez  Talat Iqbal 《Acta Geophysica》2017,65(5):919-930

Earthquake prediction study is carried out for the region of northern Pakistan. The prediction methodology includes interdisciplinary interaction of seismology and computational intelligence. Eight seismic parameters are computed based upon the past earthquakes. Predictive ability of these eight seismic parameters is evaluated in terms of information gain, which leads to the selection of six parameters to be used in prediction. Multiple computationally intelligent models have been developed for earthquake prediction using selected seismic parameters. These models include feed-forward neural network, recurrent neural network, random forest, multi layer perceptron, radial basis neural network, and support vector machine. The performance of every prediction model is evaluated and McNemar’s statistical test is applied to observe the statistical significance of computational methodologies. Feed-forward neural network shows statistically significant predictions along with accuracy of 75% and positive predictive value of 78% in context of northern Pakistan.  相似文献   

Revisiting an old profile: an updated geoarchaeological study at Nasera Rockshelter (Tanzania)     

David Manuel MartÍn-Perea  JosÉ-Manuel MaÍllo-FernÁndez  Alicia Medialdea  Juan MarÍn  Irene Solano-MegÍas  Agness Gidna  Audax Mabulla 《第四纪科学杂志》2020,35(7):951-960

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The environment of early Mars and the missing carbonates     

David C. FERNÁNDEZ‐REMOLAR  Mónica SÁNCHEZ‐ROMÁN  Andrew C. HILL  David GÓMEZ‐ORTÍZ  Olga Prieto BALLESTEROS  Christopher S. ROMANEK  Ricardo AMILS 《Meteoritics & planetary science》2011,46(10):1447-1469

Abstract– A model is presented in which the aqueous conditions needed to generate phyllosilicate minerals in the absence of carbonates found in the ancient Noachian crust are maintained by an early CO₂‐rich atmosphere, that, together with iron (II) oxidation, would prevent carbonate formation at the surface. After cessation of the internal magnetic dynamo, a CO₂‐rich primordial atmosphere was stripped by interactions with the solar wind and surface conditions evolved from humid to arid, with ground waters partially dissolving subsurface carbonate and sulfide minerals to produce acid‐sulfate evaporitic deposits in areas with upwelling ground water. In a subsequent geochemical state (Late Noachian to Hesperian), surface and subsurface acidic solutions were neutralized in the subsurface through interaction with basaltic crust, allowing the precipitation of secondary carbonates. This model suggests that, in the early Noachian, the surface waters of Mars maintained acidity because of a drop in temperature. This would have favored increased dissolution of CO₂ and a reduction in atmospheric pressure. In this scenario, physicochemical conditions precluded the formation of surface carbonates, but induced the precipitation of carbonates in the subsurface.  相似文献