Possibility of investigation of the microstreams and associations by the radiotomographic method     

O. I. Evdokimov  T. K. Filimonova  V. V. Sidorov  Rasim Amer Ali 《Earth, Moon, and Planets》1995,68(1-3):267-275

This article contains the tomographic problem's solution of the radiants distribution study by the meteor radar data. It was received the distribution of meteors velocities for the parts of celestial sphere with angular dimensions 10° × 10° and 1° × 1°. Was shown that the angular dimensions of most of radiants are equal 1° – 3° and larger part of the sporadic background looks like a totality of microstreams.  相似文献   

1991年3月5日的喷泉状爆发日珥及视向速度分布     

钟树华 《天文研究与技术》1995,(3)

本文介绍了１９９１年３月５日一个与３Ｎ级光学耀斑伴生的喷泉状爆发日珥。用Ｈα线观测从开始到结束整个过程共持续约５０分钟时间，日珥的最大投影高度１５．９万公里，视向速度分布表明，日珥主要以较大的速度向着观测者的运动，最大速度每秒１２０公里。  相似文献   

Waveform modelling using locked-mode synthetic and differential seismograms: application to determination of the structure of Mexico     

Joan S. Gomberg  T. Guy Masters† 《Geophysical Journal International》1988,94(2):193-218

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相速、群速和能量传播速度     

蒲明刚 《成都信息工程学院学报》1993,(4)

本文论述群速和能量传播速度的基本概念,并对相速、群速及能量传播速度的联系及区别作了讨论。  相似文献   

Attenuation and dispersion ofSH waves due to scattering by randomly distributed cracks     

Teruo Yamashita 《Pure and Applied Geophysics》1990,132(3):545-568

The effect of randomly distributed cracks on the attenuation and dispersion ofSH waves is theoretically studied. If earthquake ruptures are caused by sudden coalescence of preexisting cracks, it will be crucial for earthquake prediction to monitor the temporal variation of the crack distribution. Our aim is to investigate how the property of crack distribution is reflected in the attenuation and dispersion of elastic waves.We introduce the stochastic property, in the mathematical analysis, for the distributions of crack location, crack size and crack orientation. The crack size distribution is assumed to be described by a power law probability density (p(a) a ^– fora _minaa _max according to recent seismological and experimental knowledge, wherea is a half crack length and the range 13 is assumed. The distribution of crack location is assumed to be homogeneous for the sake of mathematical simplicity, and a low crack density is assumed. The stochastic property of each crack is assumed to be independent of that of the other cracks. We assume two models, that is, the aligned crack model and the randomly oriented crack model, for the distribution of crack orientation. All cracks are assumed to be aligned in the former model. The orientation of each crack is assumed to be random in the latter model, and the homogeneous distribution is assumed for the crack orientation. The idea of the mean wave formalism is employed in the analysis, and Foldy's approximation is assumed.We observe the following features common to both the aligned crack model and the randomly oriented crack model. The attenuation coefficientQ ^–1 decays in proportion tok ^–1 in the high frequency range and its growth is proportional tok ² in the low frequency range, wherek is the intrinsic wave number. This asymptotic behavior is parameter-independent, too. The attenuation coefficientQ ^–1 has a broader peak as increases and/ora _min/a _max decreases. The nondimensional peak wave numberk _p a _max at whichQ ^–1 takes the peak value is almost independent ofa _min/a _max for =1 and 2 while it considerably depends ona _min/a _max for =3. The phase velocity is almost independent ofk in the rangeka _max<1 and increases monotonically ask increases in the rangeka _max>1. While the magnitude ofQ ^–1 and the phase velocity considerably depend on the orientation of the crack in the aligned crack model, the above feature does not depend on the crack orientation.The accumulation of seismological measurements suggests thatQ ^–1 ofS waves has a peak at around 0.5 Hz. If this observation is combined with our theoretical results onk _p a _max, the probable range ofa _max of the crack distribution in the earth can be estimated for =1 or 2. If we assume 4 km/sec as theS wave velocity of the matrix medium,a _max is estimated to range from 2 to 5 km. We cannot estimatea _max in a narrow range for =3.  相似文献   

GVAD技术及其在新一代天气雷达中的应用   总被引：1，自引：1，他引：0  

李瑞义  杨洪平  赵坤  李锐锋 《气象》2018,44(4):511-517

天气雷达中VAD技术可求取雷达站上空水平风垂直廓线,梯度VAD技术(简称GVAD技术)为克服传统VAD技术受速度模糊影响较大而被提出。文中首先从理论上对GVAD技术进行模拟分析,再将其应用于新一代天气雷达实际探测的台风与大范围强降水速度模糊个例,分析其应用效果。理论模拟表明,GVAD技术较传统VAD技术可有效克服速度模糊对反演水平风垂直廓线的影响,加入的模拟噪声,也通过低通滤波方法有效抑制;在两次实际应用个例中,GVAD技术可较好克服速度模糊影响,但方位径向速度中的小波动或者噪声会在径向速度方位梯度中放大,尽管利用低通滤波进行了平滑,但其对反演水平风精度有较大影响,尤其影响水平风速反演精度,在个例中GVAD技术反演风速较传统VAD技术平均偏弱2~3m·s~(-1),模拟部分方位缺失并不影响GVAD技术的反演精度。需进一步研究减少新一代天气雷达径向速度资料中小波动或者噪声对GVAD技术应用影响的方法。  相似文献   

基于Endlich迭代调整的全球流函数和速度势计算及风场分解与重建     

黎爱兵  李旺  莫毅 《气象科技》2018,46(2):275-281

本文将有限区域求解流函数和速度势的Endlich迭代调整方法(E-T方法)推广至全球区域,并与常用Guass-Seidel迭代求解Poisson方程方法(G-P方法)进行了比较。结果表明:E-T方法适应于全球流函数和速度势的计算,其由内向外调整,不需严格考虑边界条件,可消除边界对计算结果的影响;E-T方法能准确分解和重建原始风场,而由于极地边界和差分格式影响,G-P方法求得的旋转风和辐散风之和不能准确重建原始风场,尤其是经向为固定边界时,两极地附近重建风场误差非常明显;E-T方法与G-P方法另一重要差异是前者利用流函数和速度势与风场偏微分关系直接进行迭代求解,不需计算涡度和散度,不但保证了重建风场的准确性,还防止了涡度和散度计算误差带来的二次污染。  相似文献   

两次强震峰值速度比及其余震分布特征     

许康生  曾文浩 《大地测量与地球动力学》2020,40(5):441-445

基于甘肃地震台网和青海地震台网对岷县-漳县MS6.6地震和门源MS6.4地震的波形记录,采用FFT方法分别计算这两次地震三分向的峰值速度,讨论分量之间峰值速度比的分布特征,进而研究其震源性质。结果表明,岷县-漳县地震具有逆冲兼左旋位错性质,南北向能量明显大于东西向;门源地震以逆冲为主,略具左旋走滑特征,两个水平分量的能量相当。结合这两次地震的余震序列分布特征及其他学者的研究结果推测,岷县-漳县地震的发震断层应该是位于临潭-宕昌断裂西北侧且与其平行的一条次级断裂;门源地震的发震断层应该是冷龙岭断裂西北侧的次级断裂,但受到冷龙岭断裂活动控制。  相似文献   

山东省乳山地区余震分布与速度结构研究     

李铂  张正帅  崔鑫  刘承雨  于澄 《大地测量与地球动力学》2020,40(9):931-935

利用山东乳山流动观测台网资料,采用双差精定位方法重新确定2014-05以来山东乳山M3.2地震余震序列的分布;在此基础上,利用双差层析成像方法反演该地区的三维速度结构模型。结果显示,乳山地区的余震序列整体呈现出圆形聚集特征,优势分布主要集中在3~8 km深度,乳山震群集中区的余震活动主要发生在破裂集中的区域,在5 km深度最为集中,说明乳山震群主要发生的区域为上地壳;研究区不同深度的P波速度变化明显。由于离已知的主断层有一定的距离,因此可以判断余震分布集中区可能是乳山断裂的分支或者是一条新的隐伏断裂。  相似文献   

叠前深度域偏移成像技术及其应用     

马国东 《中国煤炭地质》2008,(6):53-55

根据“西部煤炭资源高精度三维地震勘探技术”项目中对国内外各种深度域偏移成像方法和特点的调研成果．对各类深度域成像的算法和特点进行了总结,指出不同深度域成像算法选取原则主要依据构造复杂程度和横向速度变化情况。结合克希霍夫叠前三维深度域偏移模块说明深度域偏移原理和工作流程,并以实例说明叠前深度域成像能够解决因第四系地层厚度剧烈变化造成的下覆煤层赋存形态被扭曲、深度误差大、断层平面位置不准确等问题。该实例中,叠前深度域成像划分的煤层深度比时间域偏移剖面解释结果向下移动40多m,钻探结果证实其解释的煤层深度和断层位置比较准确。  相似文献