Time domain solution for multiple scattering and the coda envelopes     

Long-Sheng Gao  Song Lin Li 《Pure and Applied Geophysics》1990,132(1-2):123-150

This article summarizes work on multiple scattering based on models of media with randomly distributed scatterers. The scatterers are isotropic and statistically uniform. Measuring distance in terms of mean-free pathL _s and time in terms of the mean-free timesL _s/V, whereV is the velocity of scattered waves, we have more convenient dimensionless distance and time. It can be shown that after the dimensionless time equals 0.65 energy contributed from multiple scattering becomes predominant. Thus the later coda reflects the effect of multiple scattering rather than single scattering. Treating the seismic record, including starting and tail parts, as a whole, the diffusion theory predicts that at a dense distribution of scatterers and a small distance between source and receiver, codas reflect mainly intrinsicQ _i. Of course, this conclusion is coincident with the presumption of the diffusion theory,Q _s>Q _i. However, from a new integral equation of multiple scattering, which deals with the scattered waves and primary waves separately, the conclusion is similar but clearer. This article quotes the new expression for coda energy in two-dimensional space. It shows that if the receiver is close to the source, the coda decay reflects only intrinsicQ _i, then as the distance increases, effects of scatteringQ _s, are involved in the decay feature. The theoretical plots of coda decay show that it seems in most cases in the earthQ _i should not be smaller than one tenth ofQ _s.Project Sponsored by the Joint Earthquake Science Foundation of China.  相似文献   

Silent boundary for time domain wave motion analyses based on direct energy deletion     

M.O. Al-Hunaidi   《Soil Dynamics and Earthquake Engineering》1990,9(2)

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注水诱发地震的震源应力场和尾波衰减特征          下载免费PDF全文

赵根模  杨港生 《地震地质》1990,12(4):303

利用区域性台网记录测定了任邱油田注水诱发地震的震源应力场和尾波衰减特征,结果表明地壳上层有很大水平应力,断层面解受注水井附近局部原生断层影响与华北现代应力场的优势破裂方向和错动方式有差别。地震应力降分布范围为0.2—3.0巴。平均尾波Q_0值为75,属于地壳上部沉积岩层的正常情况,发现在时间上表现出与注水量增减有关的波动。在空间上表现出震群密集区Q_0值较外围区偏低的特点  相似文献   

强震前电磁波异常观测研究   总被引：1，自引：0，他引：1  

林美  李开复 《地震研究》1990,13(4):353-360

本文报导了1981年以来,特别是1985年以来架设于楚雄观测站的电磁波接收器记录到的电磁波异常现象。后出,1985年一1987年4月停记前,以观测站为中心,400公里为半径范围内,发生了18次M_L>5.0级地震,有15次地震前记录到明显异常(其余3次异常不太明显,当作无异常)。结果表明,电磁波异常观测是一种有希望的临震预报手段。  相似文献   

Effects of lateral velocity heterogeneity under the Nevada Test Site on short-periodP wave amplitudes and travel times     

Christopher S. Lynnes  Thorne Lay 《Pure and Applied Geophysics》1990,132(1-2):245-267

Short-period teleseismicP waves from the Nevada Test Site (NTS) show systematic variations in amplitudes and travel times, with low amplitudes corresponding to fast travel times, suggesting elastic focussing-defocussing effects. Also, the azimuthal amplitude and travel time patterns for events at the Pahute Mesa subsite are systematically different from those at the Yucca Flat subsite, indicating the presence of a near-source component in both the amplitude and travel-time variations. This component is isolated by removing the mean station pattern for all of NTS from the observations. A very-near-source component in the Pahute Mesa observations is also isolated by removing subsite station means from the measurements, whereas the Yucca Flat observations exhibited no coherent very-near-source component. These anomalies are back-projected through laterally homogeneous structure to form thin lens models at various depths. Travel-time delays are predicted from the amplitude variations using the equation for wavefront curvature. The long-wavelength components of the predicted and observed time delays correlate well, at depths of 25 km for the very-near-source component under Pahute Mesa and 160 km for the regional component under NTS. The time delay surfaces predicted by the amplitudes at these depths are mapped into warped velocity discontinuities suitable for the calculation of synthetic seismograms using the Kirchhoff-Helmholtz integral formulation. Both the intersite (near-source) and intrasite (very-near-source) differences in amplitudes are qualitatively predicted very well, although the range of variation is somewhat underpredicted. This deficiency is likely due to the destructive interference of anomalies inherent in back-projection to a single layer.  相似文献   

根据波速-压力关系评价岩石岩性、物性的实验研究   总被引：3，自引：1，他引：3       下载免费PDF全文

沈联蒂 《地球物理学报》1990,33(2):212-219

本文在实验室里对老爷庙油田馆陶组（Ng）油气贮层砂岩岩芯的孔隙度φ、空气渗透率κ、骨架密度ρ_ma、岩石密度ρ_b和不同有效覆盖压力△P下岩芯的声波时差△t,做了精确测量,用回归分析拟合了φ-K、φ-ρ_b、φ-△t和V-△p（△t-△p）的经验关系式;保持原始孔隙结构不变的前提下,在岩芯饱和各种矿化度的孔隙流体时测定了声波时差△t与孔隙度φ的关系.研究结果表明,当贮层的φ-K、φ-ρ_b和φ-△t相关时,可用声波时差△t或波速V解释贮层的岩性,并可反演求出贮层的φ、K和ρ_b;地层有效覆盖压力对贮层的孔隙度和波速具有明显的影响.根据V-△p曲线的变化规律,可以评价贮层的岩性和埋藏地质体的油、气储集能力.这些结果对油田地震勘探和石油测井资料的解释具有重要的参考价值,并为预测储油有利地区和评价贮层提供了一种新的途径.  相似文献   

法国Echassieres地区石英网脉中黑钨矿及其共生矿物的固溶体研究   总被引：1，自引：0，他引：1  

王汝成 《岩石矿物学杂志》1991,10(4):369-378

Echassiares石英网脉中的黑钨矿主要系钨锰矿一钨铁矿系列中的铁端员矿物一钨铁 矿，富泥但贫担，当其与妮铁矿共生时，钨铁矿可含8.91% Nb205。在该矿物中常见的元素置换 有:(1)Fe2+→Mn2+;(2)Wg6+Fe2+→Nb5+ +Fe+3 (3) 3W6+ +Fe2+ →4Nb5+。 妮铁矿呈它形，富含Ta. W,Ti。钨铁捉矿以枝状形态位于钨铁矿和妮铁矿之间，形成完整的矿物组合。Beauvoir花岗岩的侵位带入的热液交代钨铁矿是形成这种矿物组合的主要原因。同时,铅钨铁矿中的裂隙带或其边部还局部发生钨锰矿化。  相似文献   

钨—水杨基荧光酮络合物的极谱催化波研究   总被引：2，自引：0，他引：2  

夏道沛  管希云 《岩矿测试》1991,10(3):185-188

在HCl、KCl介质中,W(Ⅵ)-水杨基荧光酮络合物有一灵敏的催化波,峰电位为-1.22V(υs.SCE),W(Ⅵ)浓度在4.4×10~(-11)—4.4 ×10~(-8)mol/L范围内与峰电流呈线性关系,检测限2.2×10~(-11)mol/L。实验表明该波为氢催化波,可用于痕量或超痕量W的测定。  相似文献   

安徽铜陵地区含金硫化物矿床成矿作用     

戴瑞榕 《大地构造与成矿学》1991,15(1):23-30

铜陵地区位于华中地洼区,苏鄂地洼系。具工业价值的金矿床多赋存于地洼期次一级构造以及它们的交汇处,这是本区构造控矿的特点。近矿围岩以地台型碳酸盐岩为主,矿体明显受地层层位控制。与矿化有关的侵入岩,主要形成于地洼期(燕山早、中期)。岩体形成后叠加了成矿热液的多次活动。金的成矿作用及金矿床的形成,通常与含金丰度相对较高的地台构造层有密切的成因联系,它们提供了重要的物质来源,可认为是矿源层(Source beds)。本区各主要矿床是以地洼型岩浆期后热液作用为主的多因复成层控含金硫化物矿床。  相似文献   

The first and the second e of the extreme value distribution,EV1     

M. A. J. van Montfort  A. Otten 《Stochastic Environmental Research and Risk Assessment (SERRA)》1991,5(1):69-76

In the peak over threshold model resulting in the Extreme-value distribution, type I, (EV1) the firste of the distribution function is based on the Poisson number of exceedances, and the seconde arises from the Exponentially distributed magnitudes.This paper, on the one hand, generalises the Poisson model to the (positive and negative) Binomial distribution, and, on the other hand, the Exponential distribution is generalised to the Generalised Pareto distribution. Lack of fit with respect to the Poisson and Exponential distribution is measured by statistics derived from those which would be locally most powerful if the estimates of the location and scale parameter were equal to the true parameter values. Ways of combining both statistics are discussed.  相似文献