J.F. Larsen,C.A. Neal,J.R. Schaefer,A.M. Kaufman,and Zhong Lu: The 2008 phreatomagmatic eruption of Okmok volcano,Aleutian Islands,Alaska: chronology,deposits, and landform changes     

Natalia Pardo 《Bulletin of Volcanology》2015,77(8):1-3

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Acceleration strategies for elastic full waveform inversion workflows in 2D and 3D     

Jean Kormann  Juan E. Rodríguez  Miguel Ferrer  Albert Farrés  Natalia Gutiérrez  Josep de la Puente  Mauricio Hanzich  José M. Cela 《Computational Geosciences》2017,21(1):31-45

Full waveform inversion (FWI) is one of the most challenging procedures to obtain quantitative information of the subsurface. For elastic inversions, when both compressional and shear velocities have to be inverted, the algorithmic issue becomes also a computational challenge due to the high cost related to modelling elastic rather than acoustic waves. This shortcoming has been moderately mitigated by using high-performance computing to accelerate 3D elastic FWI kernels. Nevertheless, there is room in the FWI workflows for obtaining large speedups at the cost of proper grid pre-processing and data decimation techniques. In the present work, we show how by making full use of frequency-adapted grids, composite shot lists and a novel dynamic offset control strategy, we can reduce by several orders of magnitude the compute time while improving the convergence of the method in the studied cases, regardless of the forward and adjoint compute kernels used.  相似文献   

Optimization of photovoltaic solar power plant locations in northern Chile     

Anna Suuronen  Anssi Lensu  Markku Kuitunen  Rodrigo Andrade-Alvear  Natalia Guajardo Celis  Marcelo Miranda  Marcelo Perez  Jussi V. K. Kukkonen 《Environmental Earth Sciences》2017,76(24):824

The optimization of photovoltaic solar power plants location in Atacama Desert, Chile, is presented in this study. The study considers three objectives: (1) Find sites with the highest solar energy potential, (2) determine sites with the least impact on the environment, and (3) locate the areas which produce small social impact. To solve this task, multi-criteria decision analyses (MCDAs) such as analytical hierarchy process and ordered weighted averaging were applied in a GIS environment. In addition, survey results of social impacts were analyzed and included into the decision-making process, including landscape values. The most suitable sites for solar energy projects were found near roads and power lines throughout the study area. Large suitable areas were found also from central valley from Arica and Parinacota to the north edge of Atacama region. In Atacama region, most suitable sites were found in the Andes. On the contrary, Andes were also found to have high environmental values and scenically valuable landscapes. Moderate and low suitability were found on the coast, especially in Atacama region. Factors such as slope and distance to power lines and roads influenced largely the sensitivity analysis. Area of high suitability increased by 15% when distance to roads was excluded and 18% when distance to power lines or slope was removed. MCDA-GIS method was found to be useful and applicable to the optimization of solar power plant locations in northern Chile.  相似文献   

Regional climate simulations over South America: sensitivity to model physics and to the treatment of lateral boundary conditions using the MM5 model     

Silvina A. Solman  Natalia L. Pessacg 《Climate Dynamics》2012,38(1-2):281-300

In this study the capability of the MM5 model in simulating the main mode of intraseasonal variability during the warm season over South America is evaluated through a series of sensitivity experiments. Several 3-month simulations nested into ERA40 reanalysis were carried out using different cumulus schemes and planetary boundary layer schemes in an attempt to define the optimal combination of physical parameterizations for simulating alternating wet and dry conditions over La Plata Basin (LPB) and the South Atlantic Convergence Zone regions, respectively. The results were compared with different observational datasets and model evaluation was performed taking into account the spatial distribution of monthly precipitation and daily statistics of precipitation over the target regions. Though every experiment was able to capture the contrasting behavior of the precipitation during the simulated period, precipitation was largely underestimated particularly over the LPB region, mainly due to a misrepresentation in the moisture flux convergence. Experiments using grid nudging of the winds above the planetary boundary layer showed a better performance compared with those in which no constrains were imposed to the regional circulation within the model domain. Overall, no single experiment was found to perform the best over the entire domain and during the two contrasting months. The experiment that outperforms depends on the area of interest, being the simulation using the Grell (Kain–Fritsch) cumulus scheme in combination with the MRF planetary boundary layer scheme more adequate for subtropical (tropical) latitudes. The ensemble of the sensitivity experiments showed a better performance compared with any individual experiment.  相似文献   

New insight into the crust and upper mantle structure under Alaska   总被引：1，自引：0，他引：1  

Cheng Qi  Dapeng Zhao  Yong Chen  Natalia A. Ruppert 《Polar Science》2007,1(2-4):85-100

To better understand the seismic structure of the subducting Pacific plate under Alaska, we determined the three-dimensional P-wave velocity structure to a depth of approximately 200 km beneath Alaska using 438,146 P-wave arrival times from 10,900 earthquakes. In this study an irregular grid parameterization was adopted to express the velocity structure under Alaska. The number of grid nodes increases from north to south in the study area so that the spacing between grid nodes is approximately the same in the longitude direction. Our results suggest that the subducting Pacific slab under Alaska can be divided into three different parts based on its geometry and velocity structure. The western part has features similar to those in other subduction zones. In the central part a thick low-velocity zone is imaged at the top of the subducting Pacific slab beneath north of the Kenai Peninsula, which is believed to be most likely the oceanic crust plus an overlying serpentinized zone and the coupled Yakutat terrane subducted with the Pacific slab. In the eastern part, significant high-velocity anomalies are visible to 60–90 km depth, suggesting that the Pacific slab has only subducted down to that depth.  相似文献   

An assessment of changes in properties of steppe kurgan paleosoils in relation to prevailing climates over recent millennia     

Tatiana E. Khomutova  Tatiana S. Demkina  Alexander V. Borisov  Natalia N. Kashirskaya  Maxim V. Yeltsov  Vitaly A. Demkin 《Quaternary Research》2007,67(3):328-336

Comparative analysis of morphological and chemical properties of the soil chronosequence on Kastanozems soils in the steppe zone of the Russian Plain, which included paleosoils buried beneath kurgans erected ca. 2000 BC, AD 50, AD 200, and AD 1250 was performed to reconstruct the paleoenvironmental conditions in this archeologically important region. Paleoenvironmental dynamics were traced using the state of microbial communities of paleo and modern soils (including the dynamics of total and glucose-reactive biomass, and the abundance of microorganisms grown on selected media). We demonstrate that the share of the glucose-reactive microorganisms in the microbial community, the ecological–trophic structure, and oligotrophicity index might serve as indicators of the state of microbial communities and be used for paleoenvironmental reconstructions. The morphological–chemical and microbial properties confirm an arid period ca. 2000 BC, slightly wetter conditions ca. AD 50, and more humid conditions ca. AD 1250.  相似文献   

Decametric sounding of near Earth plasma: correlation and fractal analysis of scintillation data     

Natalia Muravieva  Yury Tokarev 《Astrophysics and Space Science》2001,277(1-2):331-334

Solar wind observations by means of bi-static decametric radar SURA-WIND allow studying a fine structure of solar wind plasma irregularities with resolution up to 40 km. Spectral analysis and Hurst exponents method were applied to analyze the scintillation of radio signal transmitted through turbulent layers of Ionosphere and Solar wind plasma. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Late Pleistocene Environments of the Central Ukraine     

Denis-Didier Rousseau  Natalia Gerasimenko  Zhanna Matviischina  George Kukla 《Quaternary Research》2001,56(3):349

The Vyazivok loess sequence from the Dnieper Plain, Ukraine, documents regional environmental changes during the late Pleistocene and Holocene. Pedological and palynological analyses and low-field magnetic susceptibility document changes from dense temperate forest during the last interglacial maximum to open, harsh, loess–steppe during the latest Pleistocene. The Vyazivok section overlies hillwash derived from a lower Pleistocene terrace and consists of two stratified soil complexes (Kaydaky and Pryluky; marine isotope stage [MIS] 5 equivalent) separated by a layer of eolian dust (Tyasmyn silt). The lower soils in both complexes formed within forest. These soils are overlain by the Uday (MIS4) and Bug (MIS2) loess units, which are separated by boreal soils of the Vytachiv (MIS3) complex. The coldest conditions within the record occurred in the youngest loess. Holocene soils cap the Bug loess. The Vyazivok section shows remarkable similarities with other classical loess sequences in western Europe, the Czech Republic, and Austria. The Kaydaky, Pryluky, and Vytachiv deposits, correlate with the PKIII, PKII, and PKI soil complexes, respectively, of the Czech Republic. The Tyasmyn and Prylyky silt layers correspond to marker horizons from central Europe.  相似文献   

The role of the Kazakhstan orocline in the late Paleozoic amalgamation of Eurasia   总被引：3，自引：0，他引：3  

Alexandra Abrajevitch  Rob Van der Voo  Mikhail L. Bazhenov  Natalia M. Levashova  Phil J.A. McCausland   《Tectonophysics》2008,455(1-4):61-76

After the 2005 Kashmir earthquake, we mapped surface ground fractures in Tangdhar, Uri, Rajouri and Punch sectors and liquefaction features in Jammu area lying close to the eastern side of the Line of Control (LOC) in Kashmir, India. The NW trending ground fractures occurred largely in the hanging wall zone of the southeastern extension of the causative fault in Tangdhar and Uri sectors. The principal compressive stress deduced from the earthquake induced ground fractures is oriented at N10°, whereas the causative Balakot–Bagh fault strikes 330°. The fault-plane solution indicates primarily SW thrusting of the causative fault with a component of strike–slip motion. The ground fractures reflect pronounced strike–slip together with some tensile component. The Tangdhar area showing left-lateral strike–slip motion lies on the hanging wall, and the Uri region showing right-lateral strike–slip movement is located towards the southeastern extension of the causative fault zone. The shear fractures are related to static stress that was responsible for the failure of causative fault. The tensile fractures with offsets are attributed to combination of both static and dynamic stresses, and the fractures and openings without offsets owe their origin due to dynamic stress. In Punch–Rajouri and Jammu area, which lies on the footwall, the fractures and liquefactions were generated by dynamic stress. The occurrence of liquefaction features in the out board part of the Himalayan range front near Jammu is suggestive of stress transfer  230 km southeast of the epicenter. The Balakot–Bagh Fault (BBF), the Muzaffarabad anticline, the rupture zone of causative fault and the zone of aftershocks — all are aligned in a  25 km wide belt along the NW–SE trending regional Himalayan strike of Kashmir region and lying between the MBT and the Riasi Thrust (Murree Thrust), suggesting a seismogenic zone that may propagate towards the southeast to trigger an earthquake in the eastern part of the Kashmir region.  相似文献   

State of the environment of urban and mining areas in the Selenga Transboundary River Basin (Mongolia Russia)     

Nikolay Kasimov  Natalia Kosheleva  Petr Gunin  Ilya Korlyakov  Olga Sorokina  Ivan Timofeev 《Environmental Earth Sciences》2016,75(18):1283

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