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1.
目前,国内在数字化地震资料研究中,主要应用S波来研究震源参数.本文充分利用上海数字化地震台阵(网)资料,挑选了2001～2004年华东地区发生的9个震级较大的中等地震,反演了单台记录垂直向纵波(P波)及横波(S波)震源谱,根据布龙模型,计算每个地震单台拐角频率、地震矩、零频谱值、震源破裂半径、应力降等参数,求出每个地震的震源参数(P波和S波)的平均值及其均方差,对这9个地震的P波、S波震源参数计算结果进行了对比.结果表明,用P波段数据进行震源参数的研究是可行的. 相似文献
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Because of weak dissipation effects, swells generated by fierce storms can propagate across an entire ocean basin; therefore, observing swell generation and decay and retrieving storm characteristics from a swell by satellite remote sensing are possible. In this study, based on the dispersion relation and geometrical optics principle, we used SAR wave mode data from 2003 to 2010 provided by GlobWave to track swells with peak wavelengths of more than 300 m to locate a storm-generated far-traveling swell and present the swell field related to this “static” origin. Through a comparison with ECMWF wind datasets, we conducted validations and explored some conditions that cause misjudgments in swell origins. Finally, we obtained the spatiotemporal distribution characteristics of satellite-observed swell origins (i.e., the fierce wind condition) and their evolution. This work can be used as a reference for wave models, providing early swell warnings, determining air-sea surface interactions, and determining global climate change. 相似文献
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In hydraulic fracturing experiments, perforation shots excite body and tube waves that sample, and thus can be used to characterize, the surrounding medium. While these waves are routinely employed in borehole operations, their resolving power is limited by the experiment geometry, the signal‐to‐noise ratio, and their frequency content. It is therefore useful to look for additional, complementary signals that could increase this resolving power. Tube‐to‐body‐wave conversions (scattering of tube to compressional or shear waves at borehole discontinuities) are one such signal. These waves are not frequently considered in hydraulic fracture settings, yet they possess geometrical and spectral attributes that greatly complement the resolution afforded by body and tube waves alone. Here, we analyze data from the Jonah gas field (Wyoming, USA) to demonstrate that tube‐to‐shear‐wave conversions can be clearly observed in the context of hydraulic fracturing experiments. These waves are identified primarily on the vertical and radial components of geophones installed in monitoring wells surrounding a treatment well. They exhibit a significantly lower frequency content (10–100 Hz) than the primary compressional waves (100–1000 Hz). Tapping into such lower frequencies could help to better constrain velocity in the formation, thus allowing better estimates of fracture density, porosity and permeability. Moreover, the signals of tube‐to‐shear‐wave conversion observed in this particular study provide independent estimates of the shear wave velocity in the formation and of the tube wave velocity in the treatment well. 相似文献
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Ocean Dynamics - In this study, the relation between rogue wave occurrence statistics and properties of the directional wind-wave spectrum is investigated. The study is conducted by means of the... 相似文献
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Errors in the kinematic wave and diffusion wave approximations for time-independent (or steady-state) cases of channel flow were derived for three types of boundary conditions: zero flow at the upstream end, and critical flow depth and zero depth gradient at the downstream end. The diffusion wave approximation was found to be in excellent agreement with the dynamic wave approximation, with errors in the range 1–2% for values of KF (? 7.5), where K is the kinematic wave number and F0 is the Froude number. Even for small values of KF (e.g. KF20 = 0.75), the errors were typically less than 15%. The accuracy of the diffusion wave approximation was greatly influenced by the downstream boundary condition. The error of the kinematic wave approximation was found to be less than 13% in the region 0.1 ? x ? 0.95 for KF = 7.5 and was greater than 30% for smaller values of KF (? 0.75). This error increased with strong downstream boundary control. 相似文献
7.
班公湖-怒江缝合带分隔了青藏高原拉萨地块和羌塘地块, 该带域岩样采集与分析对于该区地球物理资料深化解释、拉萨地块和羌塘地块拼贴碰撞过程的理解等均具有重要意义. 1995年在措勤盆地中采集了3条剖面、从奥陶纪至第四系不同地质年代地层岩石标本共计2500块. 通过岩石密度测试, 获得了研究区不同地质年代岩石密度测量结果. 结果表明, 岩石由老到新密度变化范围为278～253 g/cm3;各相邻地质时代间岩石密度差基本上为010 g/cm3, 白垩与侏罗、二叠与三叠之间岩石密度差最大为012～013 g/cm3 在措勤盆地内不同构造单元间岩石密度存在明显的纵横向非均一性. 相似文献
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Seismic velocity is important to migration of seismic data,interpretation of lithology and lithofacies as well asprediction of reservoir.The information of shear wave velocity is required to reduce the uncertainty for discrimi-nating lithology,identifying fluid type in porous material and calculating gas saturation in reservoir prediction.Based on Zoeppritz equations,a numeral and scanning method was proposed in this paper.Shear wave velocitycan be calculated with prestack converted wave data.The effects were demonstrated by inversion of theoreticaland real seismic data. 相似文献
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Song和Banner（2002,简称SB02）利用二维数值波浪水槽（Drimer和Agnon开发,并被Segre改进,简称DAS）研究了深水及中等水深下波群破碎,并依据波群内部能量调制和演变特性提出一个新的波浪破碎阈值.本文利用两个DAS改进模型对SB02的波浪破碎结果进行检验和比较,并研究底面斜坡坡度对SB02破碎判据的影响,其中第一个改进模型（简称MDAS1）修正了DAS中某些积分的计算错误,第二个改进模型（简称MDAS2）在自由表面上用三阶元取代原来的线性元.研究表明： MDAS1和DAS的结果非常一致;而MDAS2和MDAS1相比,波浪临界破碎时的造波板振幅、破碎时刻和局部能量极大值的最大平均变化率δmax都会发生变化,但MDAS2仍然符合SB02提出的破碎阈值.由MDAS1模拟中等水深下波群在坡度为1∶500、1∶300、1∶150和1∶100斜坡上的破碎结果表明：随着斜坡变陡,波群的局部能量极大值μ增大,δmax在临界非破碎情况下微弱变小,在临界破碎情况下急剧增大,SB02提出的破碎阈值在中等水深下坡度小于1∶100的斜坡上仍然有效. 相似文献
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Conclusion The status of various results on the determination of the appropriate family of theoretical wave spectra to describe wind generated seas and the status of various wave forecasting methods have been reviewed. The spectra of Neumann appear to describe the sea more accurately than other theoretical spectra and the wave forecasting methods of Pierson, Neumann and James appear to be the most nearly correct for the widest variety of possible wave and weather situations. 相似文献
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With the multi-wave, multi-component seismic wave exploration, one can apply the anisotropy of fracture media to analyze the attributes of the fracture media, including the fracture azimuth. In the meantime, the techniques of full-polarimetric electromagnetic wave, including full-polarimetric borehole radar, can also be used to analyze the attributes of the fracture. However, the analysis precision of both the multi-component elastic wave exploration and full-polarimetric electromagnetic wave exploration is prone to the influence of noise and other factors. So far, some researchers have conducted studies on the joint inversion of electromagnetic waves and seismic waves. This paper develops evaluation techniques of fracture azimuth by electromagnetic wave, elastic wave, and joint analysis of coincident elastic reflection and electromagnetic data. Firstly, based on the shear wave splitting of elastic waves, this paper develops a statistical analysis technique which applies Pearson correlation coefficient to count and analyze the azimuth angle of fracture. Secondly, based on the information of electromagnetic polarization rotated by fracture, this paper develops a statistical analysis method of full-polarimetric electromagnetic waves which applies the maximum amplitude ratio between the co-polarization and cross-polarization to analyze the azimuth angle of fracture. Furthermore, based on the analysis result of the elastic wave and full-polarimetric electromagnetic wave, this paper develops a joint analysis technique which adopts the standard deviation. At last, authors in this study conduct joint detection experiments on the coincident fracture medium by using the ultrasonic and full-polarimetric ground penetrating radar. The experimental result indicates that both single geophysical methods are capable of analyzing the fracture azimuth angle, but the joint analysis is more accurate. 相似文献
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常规的转换波静校正的基本思想都是从地震波的运动学特征出发,基于地表一致性假设.在地表条件复杂和地表高程相差较大的地区,它不仅无法解决严重的静校正问题,反而会带来新的畸变.本文基于频率波数域波动方程偏移原理,采用波场延拓方法实现转换波静校正,其关键点在于时间空间域和频率波数域的相对应.文中通过坐标变换将起伏地表转化为新坐标系下的水平地表,把炮点和检波点映射到同一水平面上,然后在新坐标系下推导频率域波动方程延拓公式,接着对下行波P和上行转换波SV分别利用近地表速度向上延拓到基准面,恢复起伏地表到基准面之间的真实波场,最后转换到原始坐标系取出基准面数据完成转换波静校正.通过对模拟和实际数据处理,证明该方法是正确和有效的. 相似文献
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Summary Theoretical wave spectra derived by J. Darbyshire and G. Neumann, and a modification of Neumann's results by H. U. Roll and G. Fischer are compared with a carefully computed observed spectrum and with average period, significant height, and slope observations. Observations of waves for one of the two most intense storms in the North Pacific for a 35 year period are compared with forecasts made by the Sverdrup-Munk-Bretschneider wave forecasting method, the Pierson-Neumann-James-method, and the Darbyshire method.It is shown that the Neumann spectrum agrees best with the observed spectrum. It correctly predicts the significant height, and it is consistent with average period considerations, with sea surface slope considerations, and with the properties that the sea should have when photographed. Moreover, for wave observations for one of the most intense storms in the North Pacific the Sverdrup-Munk-Bretschneider and Pierson-Neumann-James-method agree within a few feet for the significant height. The Darbyshire method is too low by more than 12 feet although the sea was not fully developed, and it would have forecast a fully developed sea.The Roll-Fischer modification leads to discrepancies with the observable characteristics of the composite wave pattern which cannot be resolved by changing the constant of the spectral function in order to adjust the total wave energy to suit the wave height characteristics.Résumé Des spectres théorétiques des vagues derivées par J. Darbyshire et G. Neumann ainsi qu'une modification par Roll-Fischer des spectres proposés par G. Neumann sont comparés à un spectre soigneusement calculé à partir des enregistrements des vagues. Les valeurs de la période moyenne apparente, de la hauteur significative des vagues et de l'angle d'inclinaison des vagues, à dériver des spectres théorétiques, permettent de les mettre en parallèle avec des observations. De plus, on confronte des observations des vagues, prises des enregistrements d'une des deux tempêtes les plus fortes qui se sont produites pendant les dernières 35 années en océan Pacifique Nord, avec les résultats obtenus grâce aux méthodes de prévision des vagues de Sverdrup-Munk-Bretschneider, de Pierson-Neumann-James et de Darbyshire.Il se montra que le spectre d'après Neumann se rapproche le plus du spectre observé. Ses résultats correspondent aux observations de l'énergie totale de la mer agitée, aux considérations de la période moyenne, à l'angle d'inclinaison des vagues et aux propriétés statistiques de la surface de la mer agitée, comme elles se laissent dériver des photographies stéréophotogrammétriques. Des observations des vagues, provenant d'une des tempêtes les plus fortes en océan Pacifique Nord, correspondent également à quelques pieds près aux prévisions effectuées d'après les méthodes de Sverdrup-Munk-Bretschneider et de Pierson-Neumann-James. Au contraire, l'application de la méthode de Darbyshire donne des hauteurs trop faibles de 12 pieds bien que cette méthode eût prédit l'entrée d'un développement complet de l'agitation de la mer en vue des conditions données par la tempête. En réalité, la mer n'atteignit pas l'état d'une agitation complètement développée et le résultat de la prévision d'après la méthode de Darbyshire eut différé encore plus fort de l'agitation réelle complètement développée de la mer, vu la grande force des vents.La modification d'après Roll-Fischer entraîne des contradictions par rapport à certaines caractéristiques de l'agitation complexe de la mer, accessibles à l'observation. Une modification de la constante de la fonction spectrale ne peut pas faire disparaître ces contradictions lors même que l'on essayerait à adapter à la caractéristique des hauteurs des vagues l'énergie totale de l'agitation de la mer.Résultats des prévisions de l'agitation de la mer. — On compare différentes méthodes en tant qu'elles se basent sur des spectres des vagues et on trouve que la méthode proposée en 1955 par Pierson-Neumann-James semble s'accorder le mieux avec les conditions observées. Cela se vérifie particulièrement lorsqu'on considère un grand nombre de situations météorologiques et des conditions de la mer agitée, offrant le plus de différences et d'extrêmes possibles.
Ausführliche Gegenüberstellung von theoretischen Wellenspektren und Methoden für die Seegangsvorhersage
Zusammenfassung Theoretische Wellenspektren nach Darbyshire und Neumann sowie nach der von Roll-Fischer vorgeschlagenen Änderung der Neumann-Spektren werden mit einem aus Seegangsregistrierungen sorgfältig berechneten Spektrum verglichen. Die aus den theoretischen Spektren abzuleitenden Werte für die mittlere scheinbare Periode, die kennzeichnende Wellenhöhe und die Neigungswinkel der wellenbewegten Meeresoberfläche lassen einen Vergleich mit den Beobachtungen zu. Außerdem werden Wellenbeobachtungen von einem der beiden stärksten Stürme innerhalb der letzten 35 Jahre im Nordpazifik den Resultaten der Seegangsvorhersage-Methoden nach Sverdrup-Munk-Bretschneider, Pierson-Neumann-James und Darbyshire gegenübergestellt.Es zeigt sich, daß das Neumann-Spektrum dem beobachteten Spektrum am nächsten kommt. Es stimmt überein mit der beobachteten Gesamtenergie des Seeganges, mit Betrachtungen über die mittlere Periode, die Neigungswinkel der Wellen und den statistischen Eigenschaften der wellenbewegten Meeresoberfläche, die man z.B. aus stereophotogrammetrischen Aufnahmen ableiten kann. Auch die Wellenbeobachtungen in einem der stärksten Stürme im Nordpazifik stimmen bis auf wenige Fuß mit den Vorausberechnungen nach den Methoden von Sverdrup-Munk-Bretschneider und Pierson-Neumann-James überein. Dagegen fallen die Höhen nach der Darbyshire-Methode um mehr als 12 Fuß zu niedrig aus, obwohl diese Methode den Seegang unter den im Sturm herrschenden Bedingungen als voll ausgereift angibt. Tatsächlich war der Seegang aber nicht voll entwickelt, und der Unterschied gegen die Darbyshire-Methode würde für voll ausgereifte See bei den hohen Windstärken noch größer sein.Die Roll-Fischer-Modifikation des Neumann-Spektrums führt zu Widersprüchen mit gewissen Eigenschaften des komplexen Seeganges, die der Beobachtung zugänglich sind. Diese Widersprüche lassen sich auch dann nicht durch Änderung der Konstanten der Spektralfunktion beseitigen, wenn man die Gesamtenergie das Seeganges der Wellenhöhencharakteristik anzupassen versucht.Ergebnisse der Seegangsvorhersage. — Methoden, soweit sie auf Wellenspektren gegründet sind, werden miteinander verglichen. Die von den Verfassern 1955 vorgeschlagene Methode scheint den beobachteten Verhältnissen am nächsten zu kommen. Dies zeigt sich besonders, wenn möglichst verschiedene und extreme Wetterlagen und Seegangsverhältnisse betrachtet werden.
Comparaison détaillée des spectres théorétiques des vagues et des méthodes de prévision des vagues相似文献
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Ocean Dynamics - An intra-measurement evaluation was undertaken, deploying a NOMAD buoy equipped with three National Data Buoy Center and two Environment and Climate Change Canada-AXYS... 相似文献
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本文理论分析了电子束沿地磁场穿越均匀、磁化等离子体密度跃变区域时,在弱磁场近似、哨声波激发、低频近似等几种典型情况下电子束流空间电荷波（Space charge wave）向电磁波的转换.先运用小信号假设求得电子束入射进均匀各向异性冷等离子体之后的色散关系和空间电荷波波数,然后借助于电磁波分量和电子束速度的边界条件,求解电子束在等离子浓度发生变化区域激发的波振幅,在几种典型情形下推导出空间电荷波转换为电磁波之间转换系数的近似解,给出了相应波辐射的坡印亭(Poynting)矢量表达式.结果表明,在渡越辐射（Transition radiation）情形下电子束可以在空间等离子体中激发出阿尔芬波（Alfven wave）和哨声波（Whistler wave）.所得结论可用于对主动空间试验结果的分析. 相似文献
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Testing dispersant effectiveness under conditions similar to that of the open environment is required for improvements in operational procedures and the formulation of regulatory guidelines. To this end, a novel wave tank facility was fabricated to study the dispersion of crude oil under regular non-breaking and irregular breaking wave conditions. This wave tank facility was designed for operation in a flow-through mode to simulate both wave- and current-driven hydrodynamic conditions. We report here an evaluation of the effectiveness of chemical dispersants (Corexit® EC9500A and SPC 1000™) on two crude oils (Medium South American [MESA] and Alaska North Slope [ANS]) under two different wave conditions (regular non-breaking and plunging breaking waves) in this wave tank. The dispersant effectiveness was assessed by measuring the water column oil concentration and dispersed oil droplet size distribution. In the absence of dispersants, nearly 8-19% of the test crude oils were dispersed and diluted under regular wave and breaking wave conditions. In the presence of dispersants, about 21-36% of the crude oils were dispersed and diluted under regular waves, and 42-62% under breaking waves. Consistently, physical dispersion under regular waves produced large oil droplets (volumetric mean diameter or VMD ? 300 μm), whereas chemical dispersion under breaking waves created small droplets (VMD ? 50 μm). The data can provide useful information for developing better operational guidelines for dispersant use and improved predictive models on dispersant effectiveness in the field. 相似文献
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We present a detailed study of Western Bohemia Love waves generated by blasts with an intention to estimate the uppermost
crust structure for a more detailed layer distribution than previous studies have used. The use of short-period (4 s and shorter)
Love waves represents a new approach in the studied region. Properties of multiple filtering as a tool of frequency–time analysis
are discussed. A new method of selecting the dispersion ridges is introduced. Tests of filtering are provided by analyzing
signals with analytically known dispersion. The isometric algorithm for the inversion problem is applied, the problem of non-uniqueness
is discussed, and tests of reliability of the inversion are presented. During the inversion, the forward problem is solved
by use of the matrix method. Six records of blasts from the Western Bohemia region are analyzed to separate the fundamental
modes of Love wavegroups, and shear wave velocity distributions down to a depth of 3.0 km are inferred. Modal summation is
used to compute synthetic velocigrams, which are compared to measured ones. The lateral heterogeneity of the region is discussed
and the presented models are compared to those of previous studies and to the geological setting of the region. 相似文献
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选择了济阳坳陷第三系地层四类不同岩性、237块典型岩心样品,在变温变压条件下进行超声波纵、横波速度及密度的测定,样品的孔隙度范围从2％到27％.根据变温变压测试数据,得出纵横波速度的压力、温度校正公式,将高温高压条件下测量的弹性参数校正到60 MPa条件,再进行密度、Vp和Vs数据分析.分析结果表明：Vp、Vs具有很好的线性相关性,得到新的密度与Vp关系式.同时将Vp、Vs关系融入到Gardner公式中,将Gardner函数推广为〖JP2〗ρ=CVApVBs的函数形式（称为广义Gardner公式）,拟合出砂岩的密度、Vp和Vs间的新关系式：ρ=1.575 8V0.287 9pV0.019 7s.〖JP〗文中讨论了该公式在横波速度预测、岩石物理模拟和AVO正反演等的作用,指出这些规律性认识可服务于油气勘探和开发. 相似文献
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Summary The nighttime and sunset LF radio wave absorption measured at Nagycenk, western Hungary over 1967–1991 is used to infer planetary wave activity and its long-term trend in the upper middle atmosphere (85 – 100 km). The very moderate positive and mostly statistically insignificant trends are consistent with the pattern provided by previous analyses of various day- and night-time absorption measurements. The trends could be of anthropogenic origin. 相似文献