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171.
Iunio Iervolino Carmine Galasso Edoardo Cosenza 《Bulletin of Earthquake Engineering》2010,8(2):339-362
In code-based seismic design and assessment it is often allowed the use of real records as an input for nonlinear dynamic
analysis. On the other hand, international seismic guidelines, concerning this issue, have been found hardly applicable by
practitioners. This is related to both the difficulty in rationally relating the ground motions to the hazard at the site
and the required selection criteria, which do not favor the use of real records, but rather various types of spectrum matching
signals. To overcome some of these obstacles a software tool for code-based real records selection was developed. REXEL, freely
available at the website of the Italian network of earthquake engineering university labs (), allows to search for suites of waveforms, currently from the European Strong-motion Database, compatible to reference spectra
being either user-defined or automatically generated according to Eurocode 8 and the recently released new Italian seismic
code. The selection reflects the provisions of the considered codes and others found to be important by recent research on
the topic. In the paper, record selection criteria are briefly reviewed first, and then the algorithms implemented in the
software are discussed. Finally, via some examples, it is shown how REXEL can effectively be a contribution to code-based
real records selection for seismic structural analysis. 相似文献
172.
Giuseppe D. Chirico Massimiliano Favalli Paolo Papale Enzo Boschi Maria Teresa Pareschi Arthur Mamou-Mani 《Bulletin of Volcanology》2009,71(4):375-387
Mt. Nyiragongo is one of the most dangerous volcanoes in the world for the risk associated with the propagation of lava flows.
In 2002 several vents opened along a huge system of fractures, pouring out lava which reached and destroyed a considerable
part of Goma, a town of about 500,000 inhabitants on the shore of Lake Kivu. In a companion paper (Favalli et al. in Bull
Volcanol, this issue, 2008) we employed numerical simulations of probable lava flow paths to evaluate the lava flow hazard on the flanks of the volcano,
including the neighbouring towns of Goma (DRC) and Gisenyi (Rwanda). In this paper we use numerical simulations to investigate
the possibility of significantly reducing the lava flow hazard in the city through the construction of protective barriers.
These barriers are added to the DEM of the area as additional morphological elements, and their effect is evaluated by repeating
numerical simulations with and without the presence of barriers. A parametric study on barrier location, size, shape and orientation
led to the identification of barriers which maximize protection while minimizing their impact. This study shows that the highest
hazard area corresponding to eastern Goma, which was largely destroyed by lava flows in 2002, cannot be effectively protected
from future lava flows towards Lake Kivu and should be abandoned. On the contrary, the rest of the town can be sheltered from
lava flows by means of two barriers that deviate or contain the lava within the East Goma sector. A proposal for the future
development of the town is formulated, whereby “new” Goma is completely safe from the arrival of lava flows originating from
vents outside its boundaries. The proposal minimizes the risk of further destruction in town due to future lava flows. 相似文献
173.
The seasonal nature of Australia’s tropical rivers means that connected groundwater aquifers are an important source of both
consumptive and non-consumptive water, particularly during the dry season. The management of these common pool groundwater
resources is one of the predominant water issues facing northern Australia. A national program of water reform stipulates
the expansion of water trading as a key instrument for water allocation. The effectiveness of new institutional arrangements
such as water markets will be determined mostly by how well they coordinate with local environmental requirements, local institutions
and local norms. This paper describes a novel application of combined field work, institutional analysis, experimental economics
and agent-based modeling to the analysis of a potential water market in the Katherine region of the Northern Territory, Australia.
The effectiveness of different versions of the policy instrument is assessed in light of local conditions. Instruments that
enable personal relationships and local institutions and norms to play a role in water management are found to be more effective
in terms of both farming income and environmental impact. 相似文献
174.
Probabilistic aftershock hazard assessment (PAHA) has been introduced by Wiemer (Geophys Res Lett 27:3405–3408, 2000). The method, in its original form, utilizes attenuation relations in evaluating peak ground velocity (PGV) exceedence probability.
We substitute the attenuation relations together with their uncertainties by strong ground motion simulations for a set of
scenarios. The main advantage of such an approach is that the simulations account for specific details of the aftershock source
effects (faulting style, slip distribution, position of the nucleation point, etc.). Mean PGVs and their standard deviations
are retrieved from the simulation results obtained by the new hybrid k-squared source model, and they are used for the PAHA analysis at a station under study. The model chosen for the testing
purposes is inspired by the Izmit A25 aftershock (M
w
= 5.8) that occurred 26 days after the mainshock. The PAHA maps are compared with (1) those obtained by the use of attenuation
relations and (2) the peak values of ten selected strong-motion recordings written by the aftershock at epicentral distances
<50 km. We conclude that, although the overall hazard decay with increasing fault distance is similar, the PAHA maps obtained
by the use of simulations exhibit remanent radiation pattern effect and prolongation in the strike direction due to the directivity
effect pronounced for some of the scenarios. As regard the comparison with real data, we conclude that the PAHA maps agree
with observed peak values due to appropriate attenuation model adopted in the analysis. 相似文献
175.
Truncation of the distribution of ground-motion residuals 总被引:1,自引:3,他引:1
Recent studies to assess very long-term seismic hazard in the USA and in Europe have highlighted the importance of the upper
tail of the ground-motion distribution at the very low annual frequencies of exceedance required by these projects. In particular,
the use of an unbounded lognormal distribution to represent the aleatory variability of ground motions leads to very high
and potentially unphysical estimates of the expected level of shaking. Current practice in seismic hazard analysis consists
of truncating the ground-motion distribution at a fixed number (ε
max) of standard deviations (σ). However, there is a general lack of consensus regarding the truncation level to adopt. This paper investigates whether
a physical basis for choosing ε
max can be found, by examining records with large positive residuals from the dataset used to derive one of the ground-motion
models of the Next Generation Attenuation (NGA) project. In particular, interpretations of the selected records in terms of
causative physical mechanisms are reviewed. This leads to the conclusion that even in well-documented cases, it is not possible
to establish a robust correlation between specific physical mechanisms and large values of the residuals, and thus obtain
direct physical constraints on ε
max. Alternative approaches based on absolute levels of ground motion and numerical simulations are discussed. However, the choice
of ε
max is likely to remain a matter of judgment for the foreseeable future, in view of the large epistemic uncertainties associated
with these alternatives. Additional issues arise from the coupling between ε
max and σ, which causes the truncation level in terms of absolute ground motion to be dependent on the predictive equation used. Furthermore,
the absolute truncation level implied by ε
max will also be affected if σ is reduced significantly. These factors contribute to rendering a truncation scheme based on a single ε
max value impractical. 相似文献
176.
我国省域工业主导产业的遴选与发展 总被引:1,自引:0,他引:1
工业主导产业在国民经济发展中起着决定性和指向性的作用。主导产业的选择是经济发展阶段的重要课题。依据6个量化指标,从4个维度对"十一五"期间主导产业进行遴选,发现以能源及相关产业为代表的重化工业是各省的重点,高新技术产业成为主导产业的省份较少,劳动密集型产业依然是东部发达省市的重点,预期中的产业转移并未实现;以行业为变量对各省份的主导产业进行聚类分析,可将31个省份划分为5类,反映了我国各省份主导产业布局特点;在此基础上,依据产业生命周期理论和各地区"十二五"发展趋势,提出了相应的对策建议。 相似文献
177.
市场经济的基本模式,是以效率为特色,兼顾市场,政府和社会作用“三位一体”的模式,本文从这一角度出发,分析了肇庆地区在市场经济导向下,尤其在珠江三角洲市场的作用下区域土地资源的开发利用优势,在此基础上探讨了区域土地资源的开发利用原则,方向与途径,并提出相应的实施措施。 相似文献
178.
大九湖钻孔记录的神农架地区中更新世晚期以来的气候环境变化 总被引:2,自引:0,他引:2
运用孢粉浓缩物AMS 14C测年和氨基酸测年方法结合气候地层对比,建立神农架地区大九湖盆地DJH-2 孔的地层年代序列。依据孢粉分析结果并结合沉积环境,将大九湖盆地中更新世晚期以来的植被演替和古气候演化划分为六个阶段:① 275.0-188.0 ka,寒冷偏干,寒温带针叶林、高山草甸;② 245.0-188.0 ka,暖湿偏干,常绿、落叶阔叶混交林;③ 188.0-129.0 ka,冷干,寒温带针叶林为主,过渡为高山草甸为主;④ 129.0-71.8 ka,暖湿,暖温带落叶阔叶林;⑤71.8-15 ka,冷干,寒温带针叶林与高山草甸间隔发育,中间有喜暖种属增多的迹象;⑥ 15.0-1.0 ka,暖湿,亚热带常绿、落叶阔叶林。孢粉组合特征及单种属特征所显示的盆地气候变化反映了良好的全球冰期、间冰期气候旋回。孢粉浓度特征反映大九湖盆地气候变化受北半球高纬冰量与低纬太阳辐射的双重控制。 相似文献
179.
180.
The Gray Fossil Site (GFS) includes a small (<2 ha) paleosinkhole lake fill with an exceptionally well-preserved record of
sedimentation and fossils from the latest Miocene to earliest Pliocene. The uppermost lacustrine stratigraphy is characterized
by rhythmites that regularly alternate between coarse-grained and organic-rich (A) laminae and fine-grained, silty clay (B)
laminae. Both the A and B components are almost exclusively comprised of exogenic sediment (including organic matter). Periodicities
of 24 and 4.4 are recorded within a continuous 96 interpreted year sequence of rhythmite sediment. In a small lake with a
poorly oxygenated bottom, the presence of laterally continuous laminated sediment that includes well-known periodicities in
rhythmite thickness is interpreted as representing annually generated varves that correspond to seasonal variations in sedimentation.
The distinctly larger fraction of medium sand-size quartz grains present within the A laminae, as well as the abrupt transitions
between A and B components suggest that the rhythmites represent deposition during alternating high-energy and lower-energy
seasons, which is consistent with a monsoonal precipitation pattern. The seasonal climate may relate to changes in the ocean
circulation pattern prior to 4.6 Ma that resulted in an increased temperature and atmospheric pressure gradient between the
east coast of North America and the Atlantic Ocean, but this climate phase seems to be only a temporary condition, as underlying
and overlying sediment are both consistent with drier conditions. The periodicity at 24 interpreted years is consistent with
the well-known Hale solar cycle. The 4.4 interpreted-year periodicity occurs within the ENSO frequency band, and if this documentation
of ENSO-like interannual climate change is correct, then it suggests that ENSO operated at times during the warm Earth conditions
characterizing the late Tertiary. 相似文献