弱裂隙各向异性对地震体波的效应   总被引：6，自引：0，他引：6  

姚陈  雷军 《中国地震》1997,13(3):232-240

由数据模拟证明，尽管对地震体波走时及纵波动力学特征来讲，弱裂隙各向异性的影响可以忽略，但与各向同性介质中的横波相比，即使对弱裂隙介质，穿透其中的横波的偏振特征也会出现显著的不同。  相似文献   

The strong ground motion in Mexico City: Analysis of data recorded by a 3D array     

Agathe Roull  Francisco J. Chvez-García 《Soil Dynamics and Earthquake Engineering》2006,26(1):71-89

In 2001, we installed 11 new accelerometers in the lake-bed zone of Mexico City, which, together with the existing stations, form a 3D array of small aperture, with 15 surface and six borehole stations. This new array recorded the 10/08/2001 Guerrero event (M=6.1) and the 01/22/2003 Colima (M=7.6) event. The analysis of these two events showed that, for periods longer than 2.5 s, the dominant wavefield is composed of a fundamental mode of surface waves arriving from the epicenter and diffracted surface waves generated at the southern boundary of the Mexican Volcanic Belt. For periods shorter than 2.5 s, the resonance of the superficial clay layer becomes predominant. The wavefield consists in a superposition of diffracted waves propagating from the western part of the valley. Our results show that the ground motion is strongly amplified by the soft clay layer but its duration is controlled by the incident wavefield.  相似文献   

Factors affecting the complex permittivity spectrum of soil at a low frequency range of 1 kHz–10 MHz     

Myounghak Oh  Yongsung Kim  Junboum Park 《Environmental Geology》2007,51(5):821-833

To establish the factors affecting the permittivity spectrum of soil in the low frequency range, the complex permittivities of soils were measured at the frequency range of 1 kHz–10 MHz. The effects of frequency, water content, soil types and heavy metal contamination on the dielectric response were evaluated and their theoretical mechanisms were discussed. Measurement distortions such as electrode polarization in the low frequency measurements were identified. The permittivity of the soil was analyzed at frequencies above 100 kHz, which was experimentally determined to be the limiting lower frequency. The real permittivities of the soils were strongly related to the volumetric water content, since it is determined by the polarizability of the free water. The effective imaginary permittivities of soils increased with volumetric water content due to the increase in conduction losses. The spatial polarization and conduction loss were found to be the main mechanism in the real and effective imaginary permittivity, respectively. Since such mechanisms are influenced by the specific surface area of the soil particles, the presence of particles with high specific surface area in the soil matrix was found to affect the permittivity of soil. Contamination of saturated soil by cationic species resulted in decreases in the real permittivity due to the decreased orientation polarization of water molecules caused by hydration of ions, but increases in the effective imaginary permittivity due to ionic conduction.  相似文献   

P波偏振层析成像   总被引：2，自引：2，他引：0  

王怀军  刘福田  陈晓非 《地球物理学进展》2000,15(3):7-13

论述了Ｐ波偏振层析成像方法。这是一个利用Ｐ波远震偏振资料去反演速度结构的方法,与走时层析成像相比,它有几个显著的优点：不受震源定位和发震时刻误差的影响;对深地幔速度结构不敏感而对接收器附近的速度结构和速度梯度最敏感,在这一意义上它与时反演是互补的。如果联合使用走时和偏振资料可以改善层析成像的结果。走时的变化对应于速度的变化,而偏振的变化则与速度梯度的变化相对应,因昆,要确定速度异常的边界,用偏振数  相似文献   

A systematic investigation of cross-validation in GWR model estimation: empirical analysis and Monte Carlo simulations   总被引：8，自引：2，他引：6  

Steven Farber  Antonio Páez 《Journal of Geographical Systems》2007,9(4):371-396

In geographically weighted regression, one must determine a window size which will be used to subset the data locally. Typically, a cross-validation procedure is used to determine a globally optimal window size. Preliminary investigations indicate that the global cross-validation score is heavily influenced by a small number of observations in the dataset. At present, the ramifications of this behaviour in cross-validation are unknown. The research reported here explores the extent to which individual and groups of observations impact optimal window size determination, and whether one can explain why some points are more influential than others. In addition, we strive to examine the impact neighbourhood specification has on model quality in terms of predictive capabilities and the ability of the method to retrieve spatially varying processes. The analysis is based on several datasets and using simulated data in order to compare and validate results. The results provide some practical guidelines for the use of cross-validation.

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Electronic Supplementary Material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Antonio PáezEmail:

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Impact spectropolarimetry in the hydrogen Hα line: present atomic data and astrophysical applications     

S. A. Kazantev  N. Feautrier  J. C. Hénoux  A. V. Liaptsev  V. V. Luchinkina 《Astronomy and Astrophysics Review》1994,6(1-2):1-17

Summary The physics of impact polarization is briefly reviewed in this paper. Methods for derivating the impact spectropolarimetric parameters relevant for the formation of H linear polarization are summarized. Spectropolarimetric techniques can provide information on the velocity distribution function of energetic particles. Since the most advanced application of this technique to astrophysics is in solar flare physics, recent results achieved by its application to particles accelerated in solar flares are presented.  相似文献   

大极距激电方法在姚家岭铜铅锌矿床深部找矿中的应用     

韩长生  欧国喜  蒋其胜 《安徽地质》2008,18(4):269-272

南陵县姚家岭铜铅锌矿床,是安徽省十五期间新发现的一处中到大型矿床,该区的物探工作,尤以激电中梯扫面和激电测深,在深部找矿中发挥了较为重要的作用,本文阐述大极距激电方法在本区寻找深部隐伏矿体的应用效果。  相似文献   

磁暴期间亚极光区极化流（SAPS）的DMSP观测与RAM模拟的比较研究          下载免费PDF全文

王慧  马淑英  A.J.Ridley 《地球物理学报》2009,52(6):1419-1428

亚极光区极化流（Subauroral Polarization Streams, SAPS）为快速流动的西向等离子体流,位于昏侧-子夜前亚极光区,是磁层-电离层-热层耦合的重要过程之一.本文利用密西根大学的RAM （Ring current-Atmosphere Interaction Model）模型对一次典型磁暴期间发生的SAPS事件进行了模拟,并与DMSP卫星观测值进行了比较.结果表明：模拟结果能大致反映观测现象;模拟得到的SAPS峰值速度所在纬度随磁暴时间的变化与观测值有较大差别;SAPS速度观测值在约18∶00 UT和约20∶00 UT左右出现两个峰值,而模拟值只有一个峰值,出现在约18∶00 UT,主要原因是模型对亚暴过程的模拟存在不足.  相似文献   

Upper mantle anisotropy beneath central and southwest Japan: An insight into subduction-induced mantle flow   总被引：1，自引：0，他引：1  

Mohamed K. Salah  T. Seno  T. Iidaka 《Journal of Geodynamics》2008,46(1-2):21-37

Analysis of seismic anisotropy in the crust and mantle wedge above subduction zones gives much information about the dynamic processes inside the Earth. For this reason, we measure shear wave polarization anisotropy in the crust and upper mantle beneath central and southwestern Japan from local shallow, intermediate, and deep earthquakes occurring in the subducting Pacific slab. We analyze S phases from 198 earthquakes recorded at 42 Japanese F-net broadband seismic stations. This data set yields a total of 980 splitting parameter pairs for central and southwestern Japan. Dominant fast polarization directions of shear waves obtained at most stations in the Kanto–Izu–Tokai areas are oriented WNW–ESE, which are sub-parallel to the subduction direction of the Pacific plate. However, minor fast polarization directions are oriented in NNE–SSW directions being parallel to the strike of the Japan Trench, especially in the north of Izu Peninsula and the northern Tokai district. Generally, fast directions obtained at stations located in Kii Peninsula and the Chubu district are oriented ENE–WSW, almost parallel to the Nankai Trough, although some fast directions have NW–SE trends. The fast directions obtained at stations in northern central Honshu are oriented N–S. Delay times vary considerably and range from 0.1 to 1.25 s depending on the source depth and the degree of anisotropy along the ray path. These lateral variations in splitting character suggest that the nature of anisotropy is quite different between the studied areas. Beneath Kanto–Tokai, the observed WNW–ESE fast directions are probably caused by the olivine A-fabric induced by the corner flow. However, the slab morphology in this region is relatively complicated as the Philippine Sea slab is overriding the Pacific slab. This complex tectonic setting may induce lateral heterogeneity in the flow and stress state of the mantle wedge, and may have produced NNE–SSW orientations of fast directions. The ENE–WSW fast directions in Kii Peninsula and the Chubu district are more coherent and may be partly induced by the subduction of the Philippine Sea plate. The N–S fast directions in northern central Honshu might be produced by the trench-parallel stretching of the wedge due to the curved slab at the arc–arc junction.  相似文献   

1999年台湾集集地震余震区——嘉义地区地震的剪切波分裂参数随时间变化的研究   总被引：7，自引：2，他引：5       下载免费PDF全文

郑秀芬  陈朝辉  张春贺 《地球物理学报》2008,51(1):149-157

本文利用台湾中央气象局布设的嘉义台CHY、民雄台CHN2和义竹台CHN8记录的地震波形资料,使用波形互相关的SAM分析方法(剪切波分裂系统分析方法),对发生在1999年9月20日台湾集集大地震（M_W7.6）余震区的嘉义M_L6.4和M_L60级地震的震前序列,开展了长达22个月的大震前近场源剪切波分裂参数随时间变化的应力预测研究.研究结果表明,在正常情况下,快剪切波的偏振方向大致近东西向,与嘉义地区最大主压应力场的方向一致,表明该区的各向异性受区域构造应力场控制;根据剪切波分裂参数——快剪切波偏振方向和慢剪切波时间延迟随时间的变化,我们认为,临震期慢剪切波时间延迟的快速下降和快剪切波偏振方向90°跳跃事件的频繁发生,可以作为临震期大震应力预测的前兆指标.近场源剪切波分裂参数随时间的变化在揭示震源区应力变化方面将发挥重大作用.  相似文献