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421.
Weights of evidence method for landslide susceptibility mapping. Prahova Subcarpathians,Romania 总被引:1,自引:0,他引:1
Iuliana Armaş 《Natural Hazards》2012,60(3):937-950
The goal of this paper is to assess the landslide susceptibility of a hilly area in the Subcarpathian sector of the Prahova
Valley, using the weight of evidence statistical method. This method aims to reduce the multitude of landslide-related conditions
to a pattern of a few discrete predictive variables. The method is based on the decision of which state is more likely to
occur grounded on the presence or absence of a predictive variable and the occurrence of an event (e.g., landslide) within
a pixel. Based on the chi-square test and the Pearson correlation applied on the data, the selected conditionally independent
variables in this study were as follows: slope gradient, slope aspect, and land use. Weights calculated individually for the three themes were added to produce a probability estimate of the area. The predictive
power of the map was tested on the basis of a split sample of landslides that were not used in the modeling process. The fact
that a great percent of the declivitous surfaces are susceptible to landslides shows the dominant manner of the evolution
of the Subcarpathian slopes, the acceleration or deceleration of the process being influenced by the land use. 相似文献
422.
Sedat İnan Alican Kop Hasan Çetin Furkan Kulak Zümer Pabuçcu Cemil Seyis Semih Ergintav Onur Tan Ruhi Saatçılar M. Nuri Bodur 《Natural Hazards》2012,62(2):575-591
Soil gas radon release patterns have been monitored continuously for more than 3 years in the Eastern Mediterranean Province (EMP) (Southern Turkey), alongside regional seismic events, providing a multidisciplinary approach. In the period from January 2008 to January 2011, 14 earthquakes M L ≥4 occurred in the study area. By monitoring the sites for more than 3 years, the site-characteristic patterns of soil radon emanation of each site have become evident. Radon emanation data show seasonal (semi-annual) variation characteristics; high soil radon values are between May and October and low soil radon values are between November and April. With available rainfall data, the soil gas radon data can be more reliably evaluated. It is shown in this paper that if radon emanation data are available over sufficiently long periods of time and baseline data (and their seasonal variations) are known with certainty for each monitoring site, then the observation of positive anomalies might provide a correlation or connection to seismic activity. 相似文献
423.
Kaolinitic clays associated with sedimentary rocks cover widespread in the Yeniköy formation from the Akhar?m district, (Afyonkarahisar, W Anatolia). Due to the proximity to the ceramic industry areas such as Kütahya and U?ak Province of Turkey, the clays in the Akhar?m district have been intensively exploited for the last few years. The Akhar?m kaolinitic clays were hosted by Middle-Upper Miocene-aged Yeniköy formation and divided into two parts as northeastern and southwestern via normal fault. The alteration degree increases from lower levels to surface in the NE part of deposit. Besides layered structure in their N70° W/30° SW direction and gray-beige, yellowish brown colored in SW part. This study focused on mineralogy, geochemistry, and ceramic properties of kaolinitic clays. X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis, chemical, physical, and mechanical tests were conducted on studied samples from the wall of clay quarry. Akhar?m clay deposits consist of mainly kaolinite and quartz. Additionally, they include smectite, biotite, feldspar, jarosite, calcite, and hematite minerals. Akhar?m clays are characterized with their moderate plasticity (PL = 17.07–24.09), low water absorption (3.64–9.53 wt.%), low linear shrinkage (8.08–15.55 wt.%), high bending strength (17.72–32.69 N/mm2), and ideal lightness values (L* = 46.50–82.74) and color values (a* = 4.71–29.87; b* = 14.67–28.72). These properties vary related with mineralogical and geochemical features of Akhar?m clays. In conclusion, Akhar?m clays have desired specifications for floor and wall t to their mineralogical, geochemical, and ceramic properties. 相似文献
424.
文70断裂带位于东濮凹陷中央隆起带文留构造带南部,油藏受文东、文70和文147三条东倾的断层控制,为东倾的断层和一系列西倾的断层形成的断块。断层切割关系复杂,造成断层组合多解性强;另外油藏含油层系多,油藏较小,油水关系复杂,油藏成因、富集规律及控制因素不明确,油藏动用困难。针对区带存在问题,运用精细地层划分与对比、RFT测试资料、HDT测井资料和三维地震解释等新技术和新方法,在强调整体解释的基础上,重点解剖了文70断裂带各断层的空间展布及组合关系,落实了构造形态和圈闭特征,并对所形成构造圈闭的含油气性及潜力进行了详细分析。结果认为,文70断裂带油气成藏主要受构造控制,发育下生上储、自生自储和古生新储三种成藏组合模式。 相似文献
425.
Iuliana Armaş 《Environmental Earth Sciences》2014,71(11):4637-4646
The aim of this study is to quantify the landslide risk for individual buildings using spatial data in a GIS environment. A landslide-prone area from Prahova Rivers’ Subcarpathian Valley was chosen because of its associated landslide hazards and its impact upon human settlements and activities. The bivariate landslide susceptibility index (LSI) was applied to calculate the spatial probability of landslides occurrence. The Landslide Susceptibility Index map was produced by numerically adding the weighted thematic maps for slope gradient and aspect, water table, soil texture, lithology, built environment and land use. Validation curves were obtained using the random-split strategy for two combinations of variables: (a) all seven variables and (b) three variables which showed highest individual success rates with respect to landslides occurrences (slope gradient, water table and land use). The principal pre-disposing factors were found to be slope steepness and groundwater table. Vulnerability was established as the degree of loss to individual buildings resulting from a potential damaging landslide with a given return period in an area. Risk was calculated by multiplying the spatial probability of landslides by the vulnerability for each building and summing up the losses for the selected return period. 相似文献
426.
427.
Finding relative satellite orbits that guarantee long-term bounded relative motion is important for cluster flight, wherein
a group of satellites remain within bounded distances while applying very few formationkeeping maneuvers. However, most existing
astrodynamical approaches utilize mean orbital elements for detecting bounded relative orbits, and therefore cannot guarantee
long-term boundedness under realistic gravitational models. The main purpose of the present paper is to develop analytical
methods for designing long-term bounded relative orbits under high-order gravitational perturbations. The key underlying observation
is that in the presence of arbitrarily high-order even zonal harmonics perturbations, the dynamics are superintegrable for
equatorial orbits. When only J
2 is considered, the current paper offers a closed-form solution for the relative motion in the equatorial plane using elliptic
integrals. Moreover, necessary and sufficient periodicity conditions for the relative motion are determined. The proposed
methodology for the J
2-perturbed relative motion is then extended to non-equatorial orbits and to the case of any high-order even zonal harmonics
(J
2n
, n ≥ 1). Numerical simulations show how the suggested methodology can be implemented for designing bounded relative quasiperiodic
orbits in the presence of the complete zonal part of the gravitational potential. 相似文献
428.
Özgür Kişi 《International Journal of Earth Sciences》2010,99(6):1471-1482
This paper proposes the application of neuro-wavelet technique for modeling daily suspended sediment–discharge relationship. The neuro-wavelet models are obtained by combining two methods, artificial neural networks (ANN) and discrete wavelet transform. The accuracy of the neuro-wavelet and the ANN models is compared with each other in suspended sediment load estimation. The daily streamflow and suspended sediment data from two stations on Tongue River in Montana are used as case studies. The comparison results reveal that the suggested model could increase the estimation accuracy. 相似文献
429.
Živana Ninčević Gladan Ivona Marasović Branka Grbec Sanda Skejić Mia Bužančić Grozdan Kušpilić Slavica Matijević Frano Matić 《Estuaries and Coasts》2010,33(2):376-383
Evaluation of a 45-year data set of primary production (PP), a 30-year data set of phytoplankton biomass, and a 51-year data
set of species composition shows an increase of phytoplankton biomass and abundance in the period from the mid-1980s to the
mid-1990s. Phytoplankton biomass showed bimodal seasonal cycles, with winter and spring maxima, which did not change over
the past 30 years. Diatoms were the most abundant functional group and they prevailed during the colder part of the year while
the dinoflagellate contribution to the phytoplankton community increased in the warmer period from May to August. Diatoms
showed a significant negative correlation with sea surface temperature (SST), while dinoflagellates were positively correlated
with SST. An increase of phytoplankton abundance, particularly dinoflagellate, in the period from the mid-1980s to the mid-1990s
coincided with years characterized by a high North Atlantic Oscillation (NAO) index. Primary production and chlorophyll a concentration in the spring period were negatively correlated with the NAO winter (DJFM) index, probably caused by increased
precipitation associated with a low or negative NAO index. PP in winter during the mixing period was positively related to
the NAO winter index associated with higher temperatures and dry conditions which brought more clear days and increased input
of solar radiation. 相似文献
430.
Ioan Seghedi Alexandru Szakács Emilian Roşu Zoltán Pécskay Katalin Gméling 《Central European Journal of Geosciences》2010,2(3):321-328
Bontâu is a major eroded composite volcano filling the Miocene Zârand extensional basin, near the junction between the Codru-Moma and Highi?-Drocea Mountains, at the tectonic boundary between the South and North Apuseni Mountains. It is a quasi-symmetric structure (16–18 km in diameter) centered on an eroded vent area (9×4 km), buttressed to the south against Mesozoic ophiolites and sedimentary deposits of the South Apuseni Mountains. The volcano was built up in two sub-aerial phases (14–12.5 Ma and 11–10 Ma) from successive eruptions of andesite lava and pyroclastic rocks with a time-increasing volatile budget. The initial phase was dominated by emplacement of pyroxene andesite and resulted in scattered individual volcanic lava domes associated marginally with lava flows and/or pyroclastic block-and-ash flows. The second phase is characterized by amphibole-pyroxene andesite as a succession of pyroclastic eruptions (varying from strombolian to subplinian type) and extrusion of volcanic domes that resulted in the formation of a central vent area. Numerous debris flow deposits accumulated at the periphery of primary pyroclastic deposits. Several intrusive andesitic-dioritic bodies and associated hydrothermal and mineralization processes are known in the volcano vent complex area. Distal epiclastic deposits initially as gravity mass flows and then as alluvial volcaniclastic and terrestrial detritic and coal filled the basin around the volcano in its western and eastern part. Chemical analyses show that lavas are calc-alkaline andesites with SiO2 ranging from 56–61%. The petrographical differences between the two stages are an increase in amphibole content at the expense of two pyroxenes (augite and hypersthene) in the second stage of eruption; CaO and MgO contents decrease with increasing SiO2. In spite of a ~4 Ma evolution, the compositions of calc-alkaline lavas suggest similar fractionation processes. The extensional setting favored two pulses of short-lived magma chamber processes. 相似文献