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991.
对地震科技档案目前在收集、接收等常规管理中存在的问题和如何解决这些问题进行了详细论述。认为,只有实现了档案材料形成积累和收集整理过程的一体化,才可保障档案材料的齐全完整,实现依法管理。 相似文献
992.
993.
根据地震构造环境和震害分布特点, 将四川及邻区划分为西南地区和四川盆地地区. 收集了西南地区96次、 四川盆地地区40次近代破坏性地震资料, 并对各次地震的震级参数进行了统一校核. 按照该地区震中烈度与震级、 有感半径与震级的统计关系, 对地震烈度衰减进行了近场与远场特征控制, 建立了地震烈度沿长轴、 短轴和平均轴的衰减关系. 统一了中国与美国面波震级的震级标度, 利用最新得出的美国西部基岩水平向地震加速度反应谱衰减关系, 采用考虑地震加速度的近场距离饱和与震级饱和特征的衰减模型, 转换得到了该地区的基岩水平向地震加速度反应谱衰减关系. 相似文献
994.
Imtiyaz A. Parvez 《Natural Hazards》2007,40(2):397-412
The Bayesian extreme-value distribution of earthquake occurrences has been used to estimate the seismic hazard in 12 seismogenic
zones of the North-East Indian peninsula. The Bayesian approach has been used very efficiently to combine the prior information
on seismicity obtained from geological data with historical observations in many seismogenic zones of the world. The basic
parameters to obtain the prior estimate of seismicity are the seismic moment, slip rate, earthquake recurrence rate and magnitude.
These estimates are then updated in terms of Bayes’ theorem and historical evaluations of seismicity associated with each
zone. From the Bayesian analysis of extreme earthquake occurrences for North-East Indian peninsula, it is found that for T = 5 years, the probability of occurrences of magnitude (M
w = 5.0–5.5) is greater than 0.9 for all zones. For M
w = 6.0, four zones namely Z1 (Central Himalayas), Z5 (Indo-Burma border), Z7 (Burmese arc) and Z8 (Burma region) exhibit high
probabilities. Lower probability is shown by some zones namely␣Z4, Z12, and rest of the zones Z2, Z3, Z6, Z9, Z10 and Z11
show moderate probabilities. 相似文献
995.
Facies reconstructions are used in hydrogeology to improve the interpretation of aquifer permeability distribution. In the absence of sufficient data to define the heterogeneity due to geological processes, uncertainties in the distribution of aquifer hydrofacies and characteristics may appear. Geometric and geostatistical methods are used to understand and model aquifer hydrofacies distribution, providing models to improve comprehension and development of aquifers. However, these models require some input statistical parameters that can be difficult to infer from the study site. A three-dimensional reconstruction of a kilometer scale fine-grain dominated Cenozoic alluvial fan derived from more than 200 continuously cored, closely spaced, and regularly distributed wells is presented. The facies distributions were reconstructed using a genetic stratigraphic subdivision and a deterministic geostatistical algorithm. The reconstruction is only slightly affected by variations in the geostatistical input parameters because of the high-density data set. Analysis of the reconstruction allowed identification in the proximal to medial alluvial fan zones of several laterally extensive sand bodies with relatively higher permeability; these sand bodies were quantified in terms of volume, mean thickness, maximum area, and maximum equivalent diameter. These quantifications provide trends and geological scenarios for input statistical parameters to model aquifer systems in similar alluvial fan depositional settings. 相似文献
996.
巨大灾害后的脆弱性:台湾集集地震后中部地区土地利用与覆盖变迁 总被引:3,自引:0,他引:3
自2004年底的南亚大海啸、美国遭受飓风侵袭以来,人类社会如何采取应对措施以降低灾害的冲击成为国际科学界的一个重要议题。台湾在几年前也遭遇巨大的地震灾害,1999年9月21日凌晨,震中发源于台湾中部、芮氏规模7.3级的巨大地震,造成全台湾2 000多人死亡,8 000多人受伤,除了造成直接的经济社会损失外,也造成山区土石松滑、地层松动与山崩,直接改变了地表的覆盖状况。在后续几年台风所带来的强风豪雨下,丰沛的降雨量使原本因地震而松滑的土石大量滑落,造成严重的土石流灾害,河床也因土石泥沙的堆积而被提升,形成严重的洪患。这些自然环境的变化不仅再次改变地表的覆盖,也使重建后的小区面临极大的灾害风险。此次冲击促使当地居民重新思考人地关系之意义,通过重建过程凝聚小区意识,发展有别于过去的土地利用形态。因此为检验当地居民对灾害的暴露程度、敏感性与适应能力,本研究采用近年来在国际环境灾害研究课题备受重视的脆弱性研究途径,并利用野外调查以及遥测与地理信息系统分析呈现地震后的土地覆盖变化。希望通过分析人与环境系统的变化,以及人类社群的社会内部固有特质,归纳出重要机制以发展降低脆弱性的策略。
研究结果显示,灾害是人与环境耦合系统(coupled system)共同形成的结果,非单一的独立事件,也不是不可避免的;且地方的脆弱性具有演化与多元化的特性,同一地方下不同族群与个体对灾害的脆弱性皆不同,因此灾害研究必须更关注于灾害发生的机制,相关的政策与策略也必须建立在更小的社会与空间单元上。 相似文献
997.
The effect of the long‐period filter cut‐off, Tc, on elastic spectral displacements is investigated using a strong ground‐motion database from Europe and the Middle East. The relation between the filter and oscillator responses is considered to observe the influence of Tc for both analogue and digital records, and the variations with site classification, magnitude, filter order and viscous damping. Robust statistics are derived using the re‐processed European data to generalize the effects of the long‐period filter cut‐off on maximum oscillator deformation demands as a function of these seismological and structural features. Statistics with a 95% confidence interval are derived to suggest usable period ranges for spectral displacement computations as a function of Tc. The results indicate that the maximum period at which spectral displacements can be confidently calculated depend strongly on the site class, magnitude and filter order. The period range where reliable long‐period information can be extracted from digital accelerograms is twice that of analogue records. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
998.
999.
Arthur Rodgers Hrvoje Tkalcic David McCallen Shawn Larsen Catherine Snelson 《Pure and Applied Geophysics》2006,163(1):55-80
We report site response in Las Vegas Valley (LVV) from historical recordings of Nevada Test Site (NTS) nuclear explosions
and earthquake recordings from permanent and temporary seismic stations. Our data set significantly improves the spatial coverage
of LVV over previous studies, especially in the northern, deeper parts of the basin. Site response at stations in LVV was
measured for frequencies in the range 0.2–5.0 Hz using Standard Spectral Ratios (SSR) and Horizontal-Vertical Spectral Ratios
(HVR). For the SSR measurements we used a reference site (approximately NEHRP B ``rock' classification) located on Frenchman
Mountain outside the basin. Site response at sedimentary sites is variable in LVV with average amplifications approaching
a factor of 10 at some frequencies. We observed peaks in the site response curves at frequencies clustered near 0.6, 1.2 and
2.0 Hz, with some sites showing additional lower amplitude peaks at higher frequencies. The spatial pattern of site response
is strongly correlated with the reported depth to basement for frequencies between 0.2 and 3.0 Hz, although the frequency
of peak amplification does not show a similar correlation. For a few sites where we have geotechnical shear velocities, the
amplification shows a correlation with the average upper 30-meter shear velocities, V30. We performed two-dimensional finite difference simulations and reproduced the observed peak site amplifications at 0.6 and
1.2 Hz with a low velocity near-surface layer with shear velocities 600–750 m/s and a thickness of 100–200 m. These modeling
results indicate that the amplitude and frequencies of site response peaks in LVV are strongly controlled by shallow velocity
structure. 相似文献
1000.
Earthquake-induced slope stability is evaluated by the force-equilibrium method in engineering practice. This method provides a safety factor against initiating failure or displacement according to the Newmark model along a fixed slip surface but it cannot evaluate failure deformations after failure occurs. An energy approach is proposed as an alternative means for evaluating slope failures and subsequent flow deformations. The driving energy for slope displacement is considered to be the earthquake energy and the gravitational potential energy. As a first step in the research, an energy balance is formulated for the model of a rigid block resting on an inclined plane. Then, an innovative model test is developed, in which the energy balance in a sliding slope is measured on a shake table. The earthquake energy used for the slope failure can be successfully quantified in the test and its contribution to displacement is discussed in the light of the energy balance established for the block model. 相似文献