Seismic motion attenuation relations in Si-chuan and adjacent areas     

雷建成高孟潭  俞言详 《地震学报(英文版)》2007,20(5):532-543

The Sichuan and adjacent areas is divided into southwest China region (SWCR) and Sichuan Basin region (SCBR) according to tectonic backgrounds and seismic damage distribution features. 96 modern destructive earthquakes in SWCR and 40 in SCBR are gathered respectively. All their magnitude parameters are checked. Based on the statis-tic relations between epicentral intensity and magnitude as well as relation between sensible radius and magnitude, the near and far field seismic intensity attenuation features are represented and controlled. And then the seismic intensity attenuation relations along major axis, minor axis and mean axis are established separately. The system-atic deviations of surface wave magnitude between China seismograph network and U.S. seismograph network are considered in this paper. By making use of the new attenuation relations of bedrock horizontal ground acceleration response spectrum in west U.S., the attenuation relations of bedrock horizontal ground acceleration response spec-trum in SWCR and SCBR are digital transformed based on the attenuation model considering acceleration satura-tion of distance and magnitude in near field.  相似文献   

Wigner-Ville分布及其在地震衰减估计中的应用   总被引：1，自引：1，他引：1  

李艳东  郑晓东 《应用地球物理》2007,4(4):245-254

地震信号的衰减一般是在频域内利用信号功率谱的统计性质进行表征。但是,传统的基于傅立叶变换的功率谱估计方法的分辨率较低,使得衰减估计的精度较低。Wigner-Ville分布是一种重要的Cohen类时频分布,它具有一系列的优良性质,如时频边缘分布性质、好的时频聚集性等。这些性质对信号的时频分析具有重要意义。因此,Wigner-Ville分布为地震信号的衰减估计提供了新的手段。本文首先介绍了Wigner-Ville分布以及能够减少或消除交叉项影响的平滑Wigner-Ville分布,然后,提出了一种基于Wigner-Ville分布的衰减估计方法。在这一方法中,利用Wigner-Ville分布得到的瞬时能量谱中高频段的能量下降速率度量衰减。将这一方法应用到塔中地区奥陶系礁滩相碳酸盐岩储层预测,结果表明,基于Wigner-Ville分布的衰减能够有效地检测出礁滩相带和泻湖区域之间衰减特性的差异。  相似文献   

The Hillarys Transect (3): Optical and chlorophyll relationships across the continental shelf off Perth     

P.R. Fearns  L. Twomey  U. Zakiyah  S. Helleren  W. Vincent  M.J. Lynch 《Continental Shelf Research》2007

An interdisciplinary study of the waters across the continental shelf off Perth, Western Australia, has provided the first detailed climatology of the physical, chemical, optical, and biological processes across the shelf. In support of this work, remote-sensing data were utilised to provide a broad view of the spatial and temporal chlorophyll concentration dynamics, to support in situ observations, and to help “fill the gaps” inherent in in situ point sampling.  相似文献   

多匝回线的自感对瞬变电磁早期信号的影响特征     

杨海燕  岳建华  胡文武  李富  刘志新 《物探化探计算技术》2007,29(2):96-98

为了研究瞬变电磁早期信号的特性,这里讨论了多匝线圈与单匝线圈的自感系数的关系,同时也分析了瞬变电磁线圈等效回路的暂态过程,以及多匝线圈感应电动势的响应特征。最后,得出了影响早期信号的因素,为提取早期数据的研究提供参考。  相似文献   

An inversion method for separating apparent and intrinsic attenuation in layered media   总被引：1，自引：0，他引：1  

I. Lerche  William Menke 《Geophysical Journal International》1986,87(2):333-347

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Predictive ground motion scaling in Switzerland: Best estimates and uncertainties     

Francesca?Bay  Stefan?WiemerEmail author  Donat?F?h  Domenico?Giardini 《Journal of Seismology》2005,9(2):223-240

Spectral ground motion (1 to 15 Hz) as a function of distance is modeled for events spanning 3.0 <M_w ≤ 7.0 in Switzerland. The parameters required to simulate ground motion with a stochastic approach are inverted from 2958 horizontal and vertical component waveforms of small to moderate size events (2.0 ≤ M_{L} ≤ 5.2) in the distance range 10 to 300 km recorded on hard rock sites. Using a Monte Carlo simulation, we establish a significantly different amplification of about a factor of 1.9 between the Alpine Foreland and the Alps. To assess the trade-off between the free parameters of our stochastic model and their influence on the predictive ground motion relationship, we perform a grid search over the five-dimensional solution space. The uncertainties are separated into epistemic and aleatory parts; the main epistemic uncertainty is attributed to the lack of data forM > 5. To constrain the viable models at large magnitudes, results from worldwide scaling studies are evaluated in light of the Swiss data. The model that explains best the low observed stress drops at small magnitudes (Δσ ≅ 3 bar) yet matches observed intensities of historical earthquakes assumes a stress drop increasing with moment asM₀^0.25. For three sites in Switzerland we evaluate the sensitivity of the epistemic uncertainty by computing probabilistic hazard curves. Our model offers the most comprehensive and detailed study of spectral ground motion for Switzerland to date.  相似文献   

Statistics of gravity waves in the lower stratosphere over Beijing based on high vertical resolution radiosonde   总被引：6，自引：0，他引：6  

BIAN Jianchun  CHEN Hongbin & LU Daren Institute of Atmospheric Sciences  Chinese Academy of Sciences  Beijing  China 《中国科学D辑(英文版)》2005,48(9):1548-1558

Atmospheric gravity waves, with small to medium scales, prevail in the atmosphere and have global ef- fects. Many researches show that gravity waves are the main source that causes the variation of wind and temperature field in the stratosphere, and that the break-up of upward propagating gravity waves is the dominant sources of small scale turbulent and mixing processes in the middle atmosphere. Theories and ob- servations indicate that the redistribution of momen- tum, caused by the generati…  相似文献   

Variation of karst spring discharge in the recent five decades as an indicator of global climate change: A case study at Shanxi,northern China   总被引：3，自引：0，他引：3  

GUO Qinghai  WANG Yanxin  MA Teng & LI Luxiu . School of Environmental Studies  China University of Geosciences  Wuhan  China  . Office of Water Resource Management of Shanxi Province  Taiyuan  China 《中国科学D辑(英文版)》2005,48(11):2001-2010

As one of the largest international scientific pro- grams in geoscience and environmental science, global change studies were initiated in the early 1980s[1,2]. Noticeable achievements have been made in the stud- ies using indicators such as loess, marine sediment, permafrost, vermicular red earth, and even magmatic activity[2―6]. In recent years, the importance of ground- water as a new type of global change indicators has caused wide attention[7]. Stochastic, isotopic and hy- drochemical st…  相似文献   

Experimental and Modelling Approaches for the Assessment of Chemical Impacts of Leachate Migration from Landfills: A Case Study of a Site on the Triassic Sandstone Aquifer in the UK East Midlands     

Steven?F.?ThorntonEmail author  John?H.?Tellam  David?N.?Lerner 《Geotechnical and Geological Engineering》2005,23(6):811-829

Current risk-based methods for assessing the effects of landfill leachate migration on groundwater resources are conservative and generalised. Cost-effective and practical strategies are required which can robustly determine the potential for contaminant attenuation on a site-specific basis. In this paper laboratory column experiments and reactive transport modelling are evaluated as a combined approach for assessing the chem’ical impact of leachate migration in the Triassic Sandstone aquifer. The results are compared with field data for a landfill in the East Midlands. Columns of aquifer sandstone were flushed sequentially with groundwater, followed by acetogenic or methanogenic leachate to simulate chemical interactions occurring during leachate loading episodes. The key contaminants in leachate (NH₄, heavy metals, organic fractions) were attenuated by ion exchange, redox reactions, sorption and degradation. These processes produce a consistent hydrochemical signature which may help identify the extent of leachate migration in the aquifer. The laboratory results largely replicate those found in the field system, and the behaviour of inorganic contaminants during leachate flushing of the aquifer columns can be described by the reactive transport model. The experimental and modelling approach presented represents a powerful tool for risk assessment and prediction of leachate contaminant fate at unlined and lined landfills.  相似文献   

Amplitude fluctuations due to diffraction and refraction in anisotropic random media: implications for seismic scattering attenuation estimates   总被引：2，自引：0，他引：2  

T. M. Müller  S. A. Shapiro 《Geophysical Journal International》2003,155(1):139-148

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