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961.
962.
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
963.
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
964.
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
965.
Paul R. Renne Alan L. Deino Willis E. Hames Matthew T. Heizler Sidney R. Hemming Kip V. Hodges Anthony A.P. Koppers Darren F. Mark Leah E. Morgan David Phillips Brad S. Singer Brent D. Turrin Igor M. Villa Mike Villeneuve Jan R. Wijbrans 《Quaternary Geochronology》2009,4(5):346-352
Data reported in 40Ar/39Ar geochronology studies are commonly insufficient to allow computation of ages. This deficiency renders it difficult to compare ages based on different standards or constants, and often hinders critical evaluation of the results. Herein are presented an enumeration of the data that should be reported in all 40Ar/39Ar studies, including a discussion in support of these requirements. The minimum required data are identified and distinguished from parameters that are useful but may be derived from them by calculation. Finally, recommendations are made for metadata needed to document age calculations (e.g., from age spectrum or isochron analyses). 相似文献
966.
An experimental investigation of the airflow structure in the near surface region over the wind-sheared air–water interface
is reported. The two-dimensional velocity fields in a plane perpendicular to the water surface were measured using particle
image velocimetry (PIV) technique over a wind speed range from 1.5 to 4.4 m s−1. The results show a reduction in the mean velocity magnitudes and the tangential stresses when gravity waves appear on the
surface. An enhanced vorticity layer was observed immediately above the water surface that extended to a height of approximately
2 cm. The vorticity was enhanced by an order of magnitude, and the energy dissipation rate was enhanced by a factor of 7 in
this layer at all wind speeds. The vertical profiles of Reynolds stress, energy production, and dissipation indicate the contribution
of surface waves in the enhanced transfer of momentum and energy between the two fluids. The results in this study show that
the flow dynamics in a layer immediately adjacent to the water surface whose thickness is of the order of the significant
wave height is significantly different from that at greater heights. Thus, it is concluded that the quantitative investigation
of the flow in the immediate vicinity of the interface is vital for an improved understanding of the heat, mass, and momentum
exchange between air and water. The present study demonstrates that PIV is an effective technique to accurately measure the
velocity fields in this region. 相似文献
967.
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
968.
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
969.
The manner in which the dynamics of geoelectric earth inhomogeneities can be studied using receiving lines oriented in different directions at a single site is considered. It is shown that the presence of a local geoelectric inhomogeneity allows monitoring the state of electric conductivity in the earth by observation of the telluric tensor. We quote results from long-continued monitoring of the electrotelluric tensor in Kamchatka. The tensor’s behavior showed an appreciable anomaly, which may have been related to great (magnitude 8.2 and 8.3) earthquakes in the Kuril-Kamchatka region. 相似文献
970.
Concepts for the Evaluation of Contaminant Mobility in Soil and Waste Materials Elution tests (S4, pHstat, and SDS test) are presented, enabling the evaluation of the mobility of hydrophilic/hydrophobic and inorganic/organic contaminants in soil and waste materials. While elution tests for estimation of the mobilization potential of hydrophilic substances are performed following the pHstat method, for hydrophobic species surfactant-containing eluents are used. The individual parameters of the elution process are selected assuming a "worst-case" scenario. In principle, because of economic reasons, detailed analytical investigations should be preceded by relevant screening tests. 相似文献