Sine-Gordon equation and its application to tectonic stress transfer     

Victor G. Bykov 《Journal of Seismology》2014,18(3):497-510

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Secondary chaotic terrain formation in the higher outflow channels of southern circum-Chryse, Mars     

J. Alexis P. Rodríguez  Jeffrey S. Kargel  David A. Crown  Alberto G. Fairén  Victor R. Baker  Pat Candelaria 《Icarus》2011,213(1):150-194

Higher outflow channel dissection in the martian region of southern circum-Chryse appears to have extended from the Late Hesperian to the Middle Amazonian Epoch. These outflow channels were excavated within the upper 1 km of the cryolithosphere, where no liquid water is expected to have existed during these geologic epochs. In accordance with previous work, our examination of outflow channel floor morphologies suggests the upper crust excavated by the studied outflow channels consisted of a thin (a few tens of meters) layer of dry geologic materials overlying an indurated zone that extends to the bases of the investigated outflow channels (1 km in depth). We find that the floors of these outflow channels contain widespread secondary chaotic terrains (i.e., chaotic terrains produced by the destruction of channel-floor materials). These chaotic terrains occur within the full range of outflow channel dissection and tend to form clusters. Our examination of the geology of these chaotic terrains suggests that their formation did not result in the generation of floods. Nevertheless, despite their much smaller dimensions, these chaotic terrains are comprised of the same basic morphologic elements (e.g., mesas, knobs, and smooth deposits within scarp-bound depressions) as those located in the initiation zones of the outflow channels, which suggests that their formation must have involved the release of ground volatiles. We propose that these chaotic terrains developed not catastrophically but gradually and during multiple episodes of nested surface collapse. In order to explain the formation of secondary chaotic terrains within zones of outflow channel dissection, we propose that the regional Martian cryolithosphere contained widespread lenses of volatiles in liquid form. In this model, channel floor collapse and secondary chaotic terrain formation would have taken place as a consequence of instabilities arising during their exhumation by outflow channel dissection. Within relatively warm upper crustal materials in volcanic settings, or within highly saline crustal materials where cryopegs developed, lenses of volatiles in liquid form within the cryolithosphere could have formed, and/or remained stable.In addition, our numerical simulations suggest that low thermal conductivity, dry fine-grained porous geologic materials just a few tens of meters in thickness (e.g., dunes, sand sheets, some types of regolith materials), could have produced high thermal anomalies resulting in subsurface melting. The existence of a global layer of dry geologic materials overlying the cryolithosphere would suggest that widespread lenses of fluids existed (and may still exist) at shallow depths wherever these materials are fine-grained and porous. The surface ages of the investigated outflow channels and chaotic terrains span a full 500 to 700 Myr. Chaotic terrains similar in dimensions and morphology to secondary chaotic terrains are not observed conspicuously throughout the surface of Mars, suggesting that intra-cryolithospheric fluid lenses may form relatively stable systems. The existence of widespread groundwater lenses at shallow depths of burial has tremendous implications for exobiological studies and future human exploration. We find that the clear geomorphologic anomaly that the chaotic terrains and outflow channels of southern Chryse form within the Martian landscape could have been a consequence of large-scale resurfacing resulting from anomalously extensive subsurface melt in this region of the planet produced by high concentrations of salts within the regional upper crust. Crater count statistics reveal that secondary chaotic terrains and the outflow channels within which they occur have overlapping ages, suggesting that the instabilities leading to their formation rapidly dissipated, perhaps as the thickness of the cryolithosphere was reset following the disruption of the upper crustal thermal structure produced during outflow channel excavation.  相似文献   

Roles of methane and carbon dioxide in geological processes on Mars     

Goro Komatsu  Gian Gabriele Ori  Marco Cardinale  James M. Dohm  Victor R. Baker  David A. Vaz  Ryo Ishimaru  Noriyuki Namiki  Takafumi Matsui 《Planetary and Space Science》2011,59(2-3):169-181

We discuss in this paper possible roles of methane and carbon dioxide in geological processes on Mars. These volatiles in the martian crust may migrate upward from their sources either directly or via various traps (structural, sedimentary, ground ice, gas hydrates). They are then likely emitted to the atmosphere by seepage or through diverse vent structures. Though gas hydrates have never been directly detected on Mars, theoretical studies favor their presence in the crust and polar caps; they could have played an important role as significant gas reservoirs in the subsurface. The martian gas hydrates would possibly be a binary system of methane and carbon dioxide occupying clathrate cavities. Landforms such as mud volcanoes with well-known linkage to gas venting are extensively distributed on Earth, and methane is the primary gas involved. Thus, identification of these landforms on Mars could suggest that methane and possibly carbon dioxide have contributed to geological processes of the planet. For example, we present a newly identified field in Chryse Planitia where features closely resembling terrestrial mud volcanoes occur widely, though with no observable activity. We also present results of a preliminary search for possible recent or present-day, methane-emission zones in the regions over which enrichments of atmospheric methane have been reported.  相似文献   

Reproductive biology of Diopatra neapolitana (Annelida,Onuphidae), an exploited natural resource in Ria de Aveiro (Northwestern Portugal)     

Adília Pires  Franck Gentil  Victor Quintino  Ana M. Rodrigues 《Marine Ecology》2012,33(1):56-65

Diopatra neapolitana Delle Chiaje, 1841 (Annelida, Onuphidae) is an important economic natural resource in Ria de Aveiro (northwestern coast of Portugal) and throughout Europe. The species is intensively harvested for use as fresh bait. However, there is only limited knowledge about its life cycle derived from a previous study in Mediterranean Sea. Reproduction and development patterns are known to vary biogeographically, making it important to base management decisions on locally appropriate information. This work examines reproduction patterns for populations from the Eastern Atlantic, which have not previously been assessed, with an eye towards drawing Atlantic–Mediterranean comparisons and informing local management strategies. The study was conducted from May 2007 to April 2009 in Ria de Aveiro. The reproductive biology of D. neapolitana was described from the proportional variation of worms with gametes in the coelom and from the progression of the oocyte diameter. Individuals with gametes inside the coelom were found all year round, but the peak reproductive period occurred between May and August, when almost all individuals had gametes in the coelom and females contained more oocytes than at any other time of the year. The overall male:female ratio was close to 1:1 and the oocyte diameter ranged from 40 to 240 μm. In vitro fertilization was performed and the results compared to other studies. Based on the present results, some protection measures are suggested to implement a sustainable exploitation of the species.  相似文献   

Soil acidity adaptive control problem     

Victor P. Yakushev  Vladimir V. Karelin  Vladimir M. Bure  Elena M. Parilina 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(6):1671-1677

Problem of soil acidity regularization is modeled as stochastic adaptive control problem with a linear difference equation of the dynamics of a field pH level. Stochastic component in the equation represents an individual time variability of soil acidity of an elementary section. We use Bayesian approach to determine a posteriori probability density function of the unknown parameters of the stochastic transition process. The Kullback–Leibler information divergence is used as a measure of difference between true distribution and its estimation. Algorithm for the construction of an adaptive stabilizing control in such a linear control system is proposed in the paper. Numerical realization of the algorithm is represented for a problem of a field soil acidity control.  相似文献   

Evaluation of the recorded ground motions for the unusual earthquake of 13 August 2006 (M w 5.3) in Michoacán México     

Alejandro Ramírez-Gaytán  Miguel A. Jaimes  William L. Bandy  Victor M. Huerfano  Ricardo A. Salido-Ruiz 《Journal of Seismology》2015,19(4):881-898

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Genotoxic potential of copper oxide nanoparticles in the bivalve mollusk <Emphasis Type="Italic">Mytilus trossulus</Emphasis>     

Victor P. Chelomin  Valentina V. Slobodskova  Maksim Zakhartsev  Sergey Kukla 《中国海洋大学学报(英文版)》2017,16(2):339-345

Copper oxide nanoparticles (CuO-NPs) are among the most widely used metal oxide nanoparticles, which increases the chance of their being released into the marine environment. As the applications of these particles have increased in recent years, their potential impact on the health of marine biota has also increased. However, the toxicological effects of these NPs in the marine environment are poorly known. In the present study, the DNA damaging potential of CuO-NPs in the marine eastern mussel Mytilus trossulus was evaluated and compared to that of dissolved copper exposures. Genotoxicity was assessed by the single cell gel electrophoresis (comet) assay in mussel gill and digestive gland cells. The results showed that copper in both forms (CuO-NPs and dissolved copper) was accumulated to different extents in mussel tissues. The mussel exposed to the dissolved copper attained higher concentrations of copper in the gills than in the digestive gland. In contrast to these results, it was found that CuO-NPs could induce much higher copper accumulation in the digestive gland than in the gills. A clear and statistically significant increase in DNA damage was found in both tissues of the Cu-exposed group compared to the control mussels. Our results indicated that the CuO-NP exposure produced remarkable effects and increased DNA damage significantly in mussel gill cells only. It should be noted that the digestive gland cells were prone to accumulation following CuO-NPs when compared to the gill cells, while the gill cells were more sensitive to the genotoxic effects of CuO-NPs. These results also suggested the need for a complete risk assessment of engineered particles before its arrival in the consumer market.  相似文献   

Coastal sediments under the influence of multiple organic enrichment sources: An evaluation using carbon and nitrogen stable isotopes   总被引：2，自引：0，他引：2  

Leandro Sampaio  Cristina Máguas  Victor Quintino 《Marine pollution bulletin》2010,60(2):272-282

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Rock slope instability assessment using spatially distributed structural orientation data in Darjeeling Himalaya (India)   总被引：1，自引：0，他引：1  

Saibal Ghosh  Andreas Günther  Emmanuel John M. Carranza  Cees J. van Westen  Victor G. Jetten 《地球表面变化过程与地形》2010,35(15):1773-1792

We discuss a geographic information system (GIS)‐based methodology for rock slope instability assessment based on geometrical relationships between topographic slopes and structural discontinuities in rocks. The methodology involves (a) regionalization of point observations of orientations (azimuth and dip) of structural discontinuities in rocks in order to generate a digital structural model (DStM), (b) testing the kinematical possibility of specific modes of rock slope failures by integrating DStMs and digital elevation model (DEM)‐derived slope and aspect data and (c) computation of stability scenarios with respect to identified rock slope failure modes. We tested the methodology in an area of 90 km² in Darjeeling Himalaya (India) and in a small portion (9 km²) within this area with higher density of field structural orientation data. The results of the study show better classification of rock slope instability in the smaller area with respect to known occurrences of deep‐seated rockslides than with respect to shallow translational rockslides, implying that structural control is more important for deep‐seated rockslides than for shallow translational rockslides. Results of scenario‐based analysis show that, in rock slopes classified to be unstable, stress‐induced rock slope instability tends to increase with increasing level of water saturation. The study demonstrates the usefulness of spatially distributed data of orientations of structural discontinuities in rocks for medium‐ to small‐scale classification of rock slope instability in mountainous terrains. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Web-oriented GIS system for monitoring, conservation and law enforcement of the Brazilian Amazon     

Carlos Moreira Souza Jr.  Kátia Pereira  Victor Lins  Sanae Haiashy  Daniel Souza 《Earth Science Informatics》2009,2(4):205-215

A web GIS (WGIS) system for the Brazilian Amazon, named ImazonGeo and based on open source and public domain data, is presented. ImazonGeo was built following three principles. First, the system is based on Spatial Data Infrastructure architecture and web interface built using free software and public domain data. Second, we went beyond visualization of maps and spatial queries by providing information obtained with spatial analysis models. To do that, we designed a database that stores the results of previously defined spatial analyses and developed customized reports and query tools to facilitate fast access of information by end-users. Finally, the system is application-oriented in the areas of forest monitoring, conservation and forest law enforcement, meaning that it aims to contribute to support the protection of Brazilian Amazon forests. We illustrate these principles by presenting ImazonGeo’s technology, architecture, content and tools. Moreover, we present two successful cases to demonstrate how the system is being used. We conclude the paper discussing the challenges and potential solutions to turning our WGIS-SDI system into an internet hub of geo-information about the Brazilian Amazon.  相似文献