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21.
The evaluation of seismic site response in the urban area of Catania was tackled by selecting test areas having peculiar lithological
and structural features, potentially favourable to large local amplifications of ground motion. The two selected areas are
located in the historical downtown and in the northern part of Catania where the presence of a fault is evident. Site response
was evaluated using spectral ratio technique taking the horizontal- to-vertical component ratio of ambient noise. Inferences
from microtremor measurements are compared with results from synthetic accelerograms and response spectra computed at all
drillings available for this area. Such method is particularly suitable in urban areas where the nature of the outcropping
geological units is masked by city growth and anthropic intervention on the surface geology. The microtremor H/V spectral
ratios evaluated at soft sites located within the downtown profile tend to be smaller than that usually reported in the literature
for such soils. A tendency for amplifications to peaks near 2 Hz is observed only in some sites located on recent alluvial
deposits. Evidences for amplifications of site effects (frequency range 4–8 Hz) were observed in the sampling sites located
on the fault, with a rapid decrease of spectral amplitude just a few tenths of metres away from the discontinuity. Numerical
simulations evidenced the importance of geolithological features at depth levels even greater than 20–30 m. Besides this,
the results strongly confirm the importance of the subsurface geological conditions, in the estimate of seismic hazard at
urban scale. 相似文献
22.
A new earthquake catalogue for central, northern and northwestern Europe with unified Mw magnitudes, in part derived from chi-square maximum likelihood regressions, forms the basis for seismic hazard calculations
for the Lower Rhine Embayment. Uncertainties in the various input parameters are introduced, a detailed seismic zonation is
performed and a recently developed technique for maximum expected magnitude estimation is adopted and quantified. Applying
the logic tree algorithm, resulting hazard values with error estimates are obtained as fractile curves (median, 16% and 84%
fractiles and mean) plotted for pga (peak ground acceleration; median values for Cologne 0.7 and 1.2 m/s2 for probabilities of exceedence of 10% and 2%, respectively, in 50 years), 0.4 s (0.8 and 1.5 m/s2) and 1.0 s (0.3 and 0.5 m/s2) pseudoacclerations, and intensity (I0 = 6.5 and 7.2). For the ground motion parameters, rock foundation is assumed. For the area near Cologne and Aachen, maps
show the median and 84% fractile hazard for 2% probability of exceedence in 50 years based on pga (maximum median value about
1.5 m/s2), and 0.4 s (>2 m/s2) and 1.0 s (about 0.8 m/s2) pseudoaccelerations, all for rock. The pga 84% fractile map also has a maximum value above 2 m/s2 and shows similarities with the median map for 0.4 s. In all maps, the maximum values fall within the area 6.2–6.3° E and
50.8–50.9° N, i.e., east of Aachen. 相似文献
23.
Dire financial constraints and the threats of forced structural reform have had the unforeseen effect of forcing municipal councils across Australia to reconsider their operational activities and organisational arrangements. With considerable ingenuity, numerous municipalities have proposed and sometimes adopted new structural formations that embody various forms of co-operative service provision. This remarkable development has unfortunately been largely ignored in the scholarly literature on Australian local government. In a modest effort aimed at remedying this neglect, the present paper seeks to outline the small, rural New South Wales Gilgandra Shire Council's (2004) ‘Co-operative/Local Government Service Company’ model, place it in the broader context of alternative models of local governance suitable for Australian conditions, and evaluate its characteristics. 相似文献
24.
Flood seasonality and generating conditions in the Tay catchment, Scotland from 1200 to present 总被引:1,自引:0,他引:1
Lindsey J McEwen 《Area》2006,38(1):47-64
The new maximum recorded river flows in Scotland since 1988 have triggered widespread interest in whether floods are becoming more frequent and in the conditions that generate floods of different magnitudes and frequencies. There are questions about the longer-term variability in flood-generating characteristics, and whether there are past analogues for present hydroclimatic variability. The present paper builds on previous work reconstructing a detailed historic flood chronology for the Tay, the largest catchment in Scotland, and its tributaries over the past 800 years, extending the gauged discharge record (1952 onwards). It categorizes flood-generating factors in the Tay catchment and analyses the hydro-meteorological conditions that have generated extreme and moderate floods over a historical period. This work is placed in a broader literature context of historical 'climaxes of storminess', periods of higher storm frequency, flood patterns observed in Scotland and Europe during the Little Ice Age and longer-term rainfall and temperature patterns. The paper concludes that the variability in flood-generating characteristics is highly dependent on the timescale of observation. Inevitably the relative dominance of winter and early spring flooding can vary from year to year and within specific time-periods, but so can the level of augmentation of the flood series with summer and autumn floods to produce notable 'flood years' and flood clusters. The Tay provides a good 'all-Scotland surrogate' for historical flood patterns, reflecting its gathering areas in eastern and western Scotland. The value of a historical approach to the assessment of flood seasonality and generating characteristics is clearly demonstrated. 相似文献
25.
新疆冰雹天气过程的基本特征 总被引:5,自引:0,他引:5
通过对新疆39a冰雹天气资料的普查,得到76次系统性冰雹天气过程和1279次局地冰雹天气过程,局地冰雹天气的发生远远多于系统性雹天气。冰雹天气过程与地形密切相关,主要发生在山区,冰雹天气以1天为主,多发生于夏季,系统性冰雹天气均由中尺度高压造成。 相似文献
26.
27.
Introduction The azimuth and slowness are two major features of seismic signals. The accurate estimation of them is quite important for both phase identification and event location. Generally, there are two types of seismic stations, i.e. 3-component stations (3C) and arrays. To estimate the two direc-tional parameters, the polarization analysis (Jurkevics, 1988) is commonly used for 3C stations and the frequency-wavenumber spectrum analysis ( f-k) (Capon, 1969; Kvaerna, Doornbos, 1986) is … 相似文献
28.
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30.
This is the second part of a contribution to the debate on the possibilities of leveraging economic globalisation — through incorporation in international production networks and global commodity chains (GCCs) — as a strategy for developing countries to industrialise and advance their position in the world economy. In the first part, we analysed the experience of the East Asian apparel industry and addressed the issues of sustaining positions, upgrading to more rewarding roles, and advancing to less dependent positions within production networks and GCCs. We developed an analytical framework at both the firm and industry levels, and subsequently identified alternative firm- and industry-level strategies and trajectories. The present paper deals with these issues in the context of the Singapore apparel industry. Based on extensive empirical research, we demonstrate that although the East Asian experience of upgrading and repositioning within the GCC is to some extent emulated in the case of the Singapore apparel industry, the outcomes have been less favourable in terms of the depth, extent and strength of these trajectories. The differing outcomes can be explained in terms of different (systemic) conditions in the Singapore business environment, including the agency of local players, the geography of sourcing networks, and the role of the state and prevailing business attitudes. Our conclusions merit continued attention in both research and policy circles on the development of capabilities at the firm level, and the role of local business and institutional environments in local industry development processes under globalisation. 相似文献