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1.
The diagenetic transformation of biogenic silica from opal-A to opal-CT was recognised on seismic reflection data over an area of 78 × 103 km2 on the mid-Norwegian margin. The opal-A/CT diagenetic boundary appears as a positive, high amplitude reflection that generally cross-cuts the hosting stratigraphy. We demonstrate that it is not a sea bottom simulating reflection (BSR) and also that is not in thermal equilibrium with the present day isotherms. We present arguments that three styles of deformation associated with the opal-A/CT reflection – polygonal faulting, regional anticlines and synclines and differential compaction folding – indicate that the silica diagenesis reaction front is fossilised at a regional scale. Isochore maps demonstrate the degree of conformity between the opal-A/CT reflection and three seismic horizons of Late Miocene to Early Pliocene age that potentially represent the paleo-seabed when ‘fossilisation’ of the reaction front took place. The seismic interpretational criteria for recognition of a fossilised diagenetic front are evaluated and the results of our study are integrated with previous studies from other basins of the NE Atlantic in order to determine if the arrest of silica diagenesis was diachronous along this continental margin. 相似文献
2.
Mid‐rise to high‐rise buildings in seismic areas are often braced by slender reinforced concrete (RC) walls, which are interconnected by RC floor diaphragms. In design, it is typically assumed that the lateral forces are distributed in proportion to the wall's elastic stiffness. Pushover analyses of systems comprising walls of different lengths have, however, shown that large compatibility forces can develop between them, which should be considered in design, but the analyses have also shown that the magnitude of the computed forces is very sensitive to the modelling assumptions. Using the results of a complex shell element model as benchmark, different simple hand‐calculation methods and inelastic beam element models are assessed and improved to yield reliable estimates of the base shear distribution among the individual walls comprising the interconnected wall system. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
Given the significant worldwide human and economic losses caused due to floods annually, reducing the negative consequences of these hazards is a major concern in development strategies at different spatial scales. A basic step in flood risk management is identifying areas susceptible to flood occurrences. This paper proposes a methodology allowing the identification of areas with high potential of accelerated surface run-off and consequently, of flash-flood occurrences. The methodology involves assessment and mapping in GIS environment of flash flood potential index (FFPI), by integrating two statistical methods: frequency ratio and weights-of-evidence. The methodology was applied for Bâsca Chiojdului River catchment (340 \(\hbox {km}^{2}\)), located in the Carpathians Curvature region (Romania). Firstly, the areas with torrential phenomena were identified and the main factors controlling the surface run-off were selected (in this study nine geographical factors were considered). Based on the features of the considered factors, many classes were set for each of them. In the next step, the weights of each class/category of the considered factors were determined, by identifying their spatial relationships with the presence or absence of torrential phenomena. Finally, the weights for each class/category of geographical factors were summarized in GIS, resulting the FFPI values for each of the two statistical methods. These values were divided into five classes of intensity and were mapped. The final results were used to estimate the flash-flood potential and also to identify the most susceptible areas to this phenomenon. Thus, the high and very high values of FFPI characterize more than one-third of the study catchment. The result validation was performed by (i) quantifying the rate of the number of pixels corresponding to the torrential phenomena considered for the study (training area) and for the results’ testing (validating area) and (ii) plotting the ROC (receiver operating characteristics) curve. 相似文献
4.
Bogdan Grecu Cristian Neagoe Dragos Tataru Felix Borleanu Bogdan Zaharia 《Journal of Seismology》2018,22(5):1275-1292
We present the first detailed investigation of the background seismic noise recorded in the Romanian-Bulgarian cross-border region over 3 years (2012–2015). We used the power spectral densities probability density functions (PSD PDFs) to study the noise variations in the period domain (0.025–1 s) as well as in the secondary microseism band (2–10 s). Strong diurnal variations and an increase of the noise levels during working days were observed at high frequencies at all stations, thus confirming the anthropic origin of the noise at low periods. The noise variations observed at longer periods (>?1 s) are relatively small among the stations and are related to season changes. The dominant feature in the noise spectra between 2 and 10 s is the double-frequency peak (DFP) whose amplitude increases and changes during winter. For a specific interval, from 25th to 27th of January 2014, when a storm was reported in the Black Sea area, the maximum of the DFP shifted from larger periods (~?5.5 s) at stations far from the Black Sea towards smaller periods (~?1.8 s) at stations located on the coastline. The polarization analysis showed that the short period double-frequency microseisms originating from the Black Sea dominate during the winter month. Finally, we showed that site conditions vary due to noise variations related to weather conditions in the Black Sea or to changes in anthropogenic noise sources. 相似文献
5.
Raluca Ciuraru Michael Ward Maxence Mendez Sylvie Gosselin Nicolas Visez Denis Petitprez 《Journal of Atmospheric Chemistry》2013,70(4):341-355
The present study focuses on the heterogeneous reaction between gaseous atomic chlorine and solid palmitic acid films, used as a proxy of the fatty acids detected in atmospheric airborne particles. This reaction is investigated in a coated wall flow tube reactor coupled to a molecular beam mass spectrometer. The reactive surfaces were prepared by coating the inner surface of the reactor. The initial Cl˙ and Cl2 uptake coefficient measured for these heterogeneous reactions is found to be fast: γo Cl?=?0.07. The rapid formation of hydrogen chloride corresponding with the disappearance of atomic chlorine is highlighted. Furthermore, the formation of new chlorinated species on the solid substrate has been detected by TOF SIMS analysis leading to an ageing process of the surface. A heterogeneous recombination of Cl atoms to Cl2 molecules was observed for aged surfaces. 相似文献
6.
The possibility that BL Lac S5 0716+714 exhibits a linear root mean square (rms)-flux relation in its IntraDay Variability (IDV) is analysed. The results may be used as an argument in the existing debate regarding the source of optical IDV in Active Galactic Nuclei. 63 time series in different optical bands were used. A linear rms-flux relation at a confidence level higher than 65 % was recovered for less than 8 % of the cases. We were able to check if the magnitude is log-normally distributed for eight timeseries and found, with a confidence ≥95 %, that this is not the case. 相似文献
7.
M. Popa M. Radulian A. Szakács I. Seghedi B. Zaharia 《Pure and Applied Geophysics》2012,169(9):1557-1573
The southern part of the southeastern Carpathians represents the site of the most recent volcanic eruptions of the entire Carpathian-Pannonian region. The products of these eruptions range from 42 to 10?Ka radiocarbon ages in the South Harghita Mountains (high K calc-alkaline rocks with adakite-like features), and at 1.2–0.6?Ma?K–Ar ages in the Per?ani Mountains (alkali basalts). They were emplaced in a post-collisional regime. Ciomadul volcano is located at the southernmost part of the NW–SE oriented C?limani-Gurghiu-Harghita range crossing the inner part of the southeastern Carpathians and in the rough proximity of the Vrancea seismic zone (at ca. 60?km toward NW). Its magma generation is attributed to geodynamic events closely related to the seismogenic area. A number of particular geophysical and geochemical features located in the study region, including (1) the abrupt attenuation of the seismic waves originating from the Vrancea intermediate-depth foci, (2) the most intense heat-flow anomaly in Romania, (3) the most prominent 3He/4He anomaly measured in natural “postvolcanic” gas emanations, are all in favor of the hypothesis of a still existing hot local magma chamber. Data acquired during recent seismic monitoring of the Vrancea zone and its neighborhoods suggest an enhancement of the local seismicity beneath the southern edge of the South Harghita Mts., both at crustal and subcrustal levels. At the same time, recent tomography images obtained using local earthquake data correlate well with the presence of a vertically extended low-velocity zone coming from the upper mantle to the assumed magmatic chambers located in the crust. The present data, supporting the presence of an active crustal magma chamber beneath Ciomadul, allow us to consider that future volcanic activity at this volcano cannot be discarded. 相似文献
8.
Mean daily streamflow records from 44 river basins in Romania with an undisturbed runoff regime have been analyzed for trends with the nonparametric Mann‐Kendall test for two periods of study: 1961–2009 (25 stations) and 1975–2009 (44 stations). The statistical significance of trends was tested for each station on an annual and seasonal basis, for different streamflow quantiles. In order to account for the presence of serial correlation that might lead to an erroneous rejection of the null hypothesis, a trend‐free prewhitening was applied to the original data series. The regional field significance of trends is tested by a bootstrap procedure. Changes in the streamflow regime in Romania are demonstrated. The main identified trends are an increase in winter and autumn streamflow since 1961 and a decrease in summer flow since 1975. The streamflow trends are well explained by recent changes in temperature and precipitation that occurred in the last 50 years. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
Policy makers are still struggling to find a rational and effective way to handle adaptation to climate change. This paper discusses a more strategic, economic approach to public adaptation and compares it with adaptation practice in Europe. An economic approach to adaptation involves setting priorities, both spatially (where to adapt) and inter-temporally (when to adapt). The paper reviews what we know about Europe’s geographic adaptation priorities. On inter-temporal priorities, it recommends fast-tracking two types of action: Win-win measures that yield an immediate return, such as water efficiency, and strategic decisions on infrastructure and spatial planning that have long-term consequences for Europe’s vulnerability profile. An economic approach to adaptation involves careful project design to ensure adaptation measures are cost-effective and flexible in the light of climate uncertainty (how to adapt). The final element of an economic approach to adaptation is the division of labour between the state and private actors (who should adapt). The paper argues that the traditional functions of the state—the provision of public goods, creation of an enabling environment and protection of the vulnerable—also apply to adaptation. 相似文献
10.
Gerardo Herrera Rosa María Mateos Juan Carlos García-Davalillo Gilles Grandjean Eleftheria Poyiadji Raluca Maftei Tatiana-Constantina Filipciuc Mateja Jemec Auflič Jernej Jež Laszlo Podolszki Alessandro Trigila Carla Iadanza Hugo Raetzo Arben Kociu Maria Przyłucka Marcin Kułak Michael Sheehy Xavier M. Pellicer Charise McKeown Graham Ryan Veronika Kopačková Michaela Frei Dirk Kuhn Reginald L. Hermanns Niki Koulermou Colby A. Smith Mats Engdahl Pere Buxó Marta Gonzalez Claire Dashwood Helen Reeves Francesca Cigna Pavel Liščák Peter Pauditš Vidas Mikulėnas Vedad Demir Margus Raha Lídia Quental Cvjetko Sandić Balazs Fusi Odd Are Jensen 《Landslides》2018,15(2):359-379
Landslides are one of the most widespread geohazards in Europe, producing significant social and economic impacts. Rapid population growth in urban areas throughout many countries in Europe and extreme climatic scenarios can considerably increase landslide risk in the near future. Variability exists between European countries in both the statutory treatment of landslide risk and the use of official assessment guidelines. This suggests that a European Landslides Directive that provides a common legal framework for dealing with landslides is necessary. With this long-term goal in mind, this work analyzes the landslide databases from the Geological Surveys of Europe focusing on their interoperability and completeness. The same landslide classification could be used for the 849,543 landslide records from the Geological Surveys, from which 36% are slides, 10% are falls, 20% are flows, 11% are complex slides, and 24% either remain unclassified or correspond to another typology. Most of them are mapped with the same symbol at a scale of 1:25,000 or greater, providing the necessary information to elaborate European-scale susceptibility maps for each landslide type. A landslide density map was produced for the available records from the Geological Surveys (LANDEN map) showing, for the first time, 210,544 km2 landslide-prone areas and 23,681 administrative areas where the Geological Surveys from Europe have recorded landslides. The comparison of this map with the European landslide susceptibility map (ELSUS 1000 v1) is successful for most of the territory (69.7%) showing certain variability between countries. This comparison also permitted the identification of 0.98 Mkm2 (28.9%) of landslide-susceptible areas without records from the Geological Surveys, which have been used to evaluate the landslide database completeness. The estimated completeness of the landslide databases (LDBs) from the Geological Surveys is 17%, varying between 1 and 55%. This variability is due to the different landslide strategies adopted by each country. In some of them, landslide mapping is systematic; others only record damaging landslides, whereas in others, landslide maps are only available for certain regions or local areas. Moreover, in most of the countries, LDBs from the Geological Surveys co-exist with others owned by a variety of public institutions producing LDBs at variable scales and formats. Hence, a greater coordination effort should be made by all the institutions working in landslide mapping to increase data integration and harmonization. 相似文献