Wave damping characteristics of vertically stratified porous structures under oblique wave action   总被引：1，自引：0，他引：1  

Sheng-Wen Twu  Cheng-Chi Liu  Chang-Wei Twu 《Ocean Engineering》2002,29(11):1295-1311

The characteristics of wave damping for the vertically stratified porous breakwaters are investigated under oblique wave action. It is found that for common angles of incidence, the wave damping efficiency of a vertically stratified porous structure behaves very similar to a simple structure. The reflection coefficient decreases with increasing angle of incidence while the transmission coefficient only slightly increases as the angle of incidence increases. It is shown that the wave energy loss is in direct proportional to the structure thickness and its porosity regardless of the angle of incidence. Considering small transmission coefficient as a basic requirement and if a moderate reflection coefficient is accepted, a structure thickness of b/h=1 is proposed. In this situation, since the structure does not have a very large thickness, adopting a vertically stratified structure is not an effective way to improve its wave damping efficiency.  相似文献   

Geophysical investigations of buried Quaternary valleys in Denmark: an integrated application of transient electromagnetic soundings, reflection seismic surveys and exploratory drillings   总被引：1，自引：0，他引：1  

Flemming Jrgensen  Holger Lykke-Andersen  Peter B. E. Sandersen  Esben Auken  Egon Nrmark 《Journal of Applied Geophysics》2003,53(4):215

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井间地震技术在松南油气开发中的初步应用研究   总被引：6，自引：1，他引：5       下载免费PDF全文

刘清林  王世库 《地球物理学报》1998,41(1):124-132

为了研究松南地区陆相砂泥岩薄互层储层岩石物性横向变化、微构造等对油气聚集的影响和探索利用高分辨率井间地震技术直接指示油气分布的可能性,开展了井间地震及地面小三维地震、VSP、测井等立体地震观测．使用了自行研制的井中炸药震源和常规地震记录仪器．采用层析成像方法、反射资料叠前偏移成像方法等对采集到的资料进行研究,得到了不同分辨率的地下构造和岩石物性信息,展示出不同方法技术在分辨薄储层能力上的差异．高分辨率的井间地震成果较好地实现了井间地层对比,查清了两井间储层横向变化和油气分布情况．层析速度与构造信息等的综合应用解释了两井油气产能差异的原因,建立了油气地质模型．所得成果显示出井间地震技术在油气开发中的潜力．  相似文献   

Seismic evidence of Caledonian deformed crust and uppermost mantle structures in the northern part of the Trans-European Suture Zone, SW Baltic Sea     

C. M. Krawczyk  F. Eilts  A. Lassen  H. Thybo 《Tectonophysics》2002,360(1-4):215-244

Collisional structures from the closure of the Tornquist Ocean and subsequent amalgamation of Avalonia and Baltica during the Caledonian Orogeny in the northern part of the Trans-European Suture Zone (TESZ) in the SW Baltic Sea are investigated. A grid of marine reflection seismic lines was gathered in 1996 during the DEKORP-BASIN '96 campaign, shooting with an airgun array of 52 l total volume and recording with a digital streamer of up to 2.1 km length. The detailed reflection seismic analysis is mainly based on post-stack migrated sections of this survey, but one profile has also been processed by a pre-stack depth migration algorithm. The data provides well-constrained images of upper crustal reflectivity and lower crustal/uppermost mantle reflections. In the area of the Caledonian suture, a reflection pattern is observed with opposing dips in the upper crust and the uppermost mantle. Detailed analysis of dipping reflections in the upper crust provides evidence for two different sets of reflections, which are separated by the O-horizon, the main decollement of the Caledonian deformation complex. S-dipping reflections beneath the sub-Permian discontinuity and above the O-horizon are interpreted as Caledonian thrust structures. Beneath the O-horizon, SW-dipping reflections in the upper crust are interpreted as ductile shear zones and crustal deformation features that evolved during the Sveconorwegian Orogeny. The Caledonian deformation complex is subdivided into (1) S-dipping foreland thrusts in the north, (2) the S-dipping suture itself that shows increased reflectivity, and (3) apparently NE-dipping downfaulted sedimentary horizons south of the Avalonia–Baltica suture, which may have been reactivated during Mesozoic normal faulting. The reflection Moho at 28–35 km depth appears to truncate a N-dipping mantle structure, which may represent remnant structures from Tornquist Ocean closure or late-collisional compressional shear planes in the upper mantle. A contour map of these mantle reflections indicates a consistent northward dip, which is steepest where there is strong bending of the Caledonian deformation front. The thin-skinned character of the Caledonian deformation complex and the fact that N-dipping mantle reflections do not truncate the Moho indicate that the Baltica crust was not mechanically involved in the Caledonian collision and, therefore, escaped deformation in this area.  相似文献   

The reflection of water waves by shear currents     

W. D. McKee 《Pure and Applied Geophysics》1977,115(4):937-949

The refraction and reflection of linear water waves entering a following jet-type current is considered. A short-wave asymptotic solution is presented and the reflection coefficient found. This varies continuously from zero when the waves are normal to the current to unity when they are very oblique to it. The trapping of waves by an opposing current is also considered.  相似文献   

Reflection seismic imaging and physical properties of base-metal and associated iron deposits in the Bathurst Mining Camp, New Brunswick, Canada   总被引：1，自引：0，他引：1  

Alireza Malehmir  Gilles Bellefleur 《Ore Geology Reviews》2010,38(4):319-333

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安徽贵池矿集区深部精细结构——来自综合地球物理探测结果的认识   总被引：2，自引：1，他引：1       下载免费PDF全文

邵陆森  刘振东  吕庆田  严加永  张昆  赵金花  祁光  张亚伟 《地球物理学报》2015,58(12):4490-4504

安徽贵池矿集区是长江中下游成矿带中重要的铜多金属矿集区,随着浅表找矿难度的加大,急需了解矿集区深部结构为深部找矿提供深部找矿提供指示.为揭示贵池矿集区深部地壳结构格架、控岩、控矿构造和岩浆系统的空间结构,深化对成矿作用的认识,在该区实施了两条长度各约60km垂直于构造走向的反射地震和MT探测剖面,通过对MT数据有针对性的去噪和反演,获得了研究区10km以浅的地电结构;通过对反射数据的层析反演静校正、叠前保幅多域去噪、精细速度分析和叠前时间偏移等处理,获取了该地区地壳结构的地震成像剖面.结合区域地质构造背景和针对性处理的区域重磁数据,对两条综合探测剖面的反演处理结果进行了分析与解释,研究发现了本区地层的构造反射特征、地壳结构特征和Moho特征,厘定了盖层与基底之间的区域滑脱面、中下地壳滑脱面和Moho面的深度和形态.发现了地壳上冲和俯冲的反射特征,可能是华夏块体与扬子块体晋宁期发生板内碰撞的痕迹.高坦断裂是一个深达地壳级的断裂,其南北两侧具有不同的重磁特征、电性结构特征和地震反射特征,该断裂可能是深部流体上涌的通道,岩浆和地幔热液沿断裂上涌并沿地层和裂隙侵入中上地壳,形成岩基或岩体,或与围岩发生强烈矿化作用形成贵池矿集区多金属矿床.  相似文献   

辽西兴城地区深反射地震剖面初步研究   总被引：1，自引：1，他引：0       下载免费PDF全文

姜弢  徐学纯  贾海青  葛利华 《地球物理学报》2014,57(9):2833-2845

为了分析和研究辽西兴城地区深部地下结构,深部探测与实验研究专项SinoProbe在辽西进行了深反射地震实验研究.本文报告了在辽西东部进行的一次二维近垂直深反射地震实验结果,测线西起葫芦岛市西老爷庙村,东至兴城市区外首山附近的郭家店,方向约为北偏西33°,剖面全长21.93 km.在共中心点叠加剖面发现了5个主要反射波组,分别出现在双程走时6 s,6.5 s,7.5 s,8 s,10.4 s左右.论文对主要反射波组地球物理特征进行了描述、分析,并结合邻区深部地震资料研究成果,得出三点认识：一是研究区域地壳可分为上、下两层结构,上地壳内无明显反射层位,下地壳呈现“凹陷”特征;二是观测到来自莫霍面反射信号（10.4 s TWT）,对应莫霍面深度约为30 km左右（速度按地壳平均速度6 km/s折算）,莫霍面西深东浅,东部较西部约抬升600 m;三是本区域莫霍面可能由一组横向速度、厚度不一致的多个薄层构成.  相似文献   

A massive, dusty toroid with large grains in the pre-planetary nebula IRAS22036+5306     

R. Sahai  K. Young  N. Patel  C. Sánchez Contreras  M. Morris 《Astrophysics and Space Science》2008,313(1-3):241-244

Using the Submillimeter Array (SMA), we have obtained high angular-resolution (∼1″) interferometric maps of the submillimeter (0.88 mm) continuum and CO J=3–2 line from IRAS 22036+5306 (I 22036), a bipolar pre-planetary nebula (PPN) with knotty jets discovered in our HST SNAPshot survey of young PPNe. In addition, we have obtained supporting lower-resolution (∼10″) 2.6 mm continuum and CO, ¹³CO J=1–0 observations with the Owens Valley Radio Observatory (OVRO) interferometer. We find an unresolved source of submillimeter (and millimeter-wave) continuum emission in I 22036, implying a very substantial mass (0.02–0.04M _⊙) of large (i.e., radius ≳1 mm), cold (≲50 K) dust grains associated with I 22036’s toroidal waist. The CO J=3–2 observations show the presence of a very fast (∼220 km s⁻¹), highly collimated, massive (0.03M _⊙) bipolar outflow with a very large scalar momentum (about 10³⁹ g cm s⁻¹), and the characteristic spatio-kinematic structure of bow-shocks at the tips of this outflow. The fast outflow in I 22036, as in most PPNe, cannot be driven by radiation pressure. The large mass of the torus suggests that it has most likely resulted from common-envelope evolution in a binary, however it remains to be seen whether or not the time-scales required for the growth of grains to millimeter sizes in the torus are commensurate with such a formation scenario. The presence of the torus should facilitate the formation of the accretion disk needed to launch the jet. We also find that the ¹³C/¹²C ratio in I 22036 is very high (0.16), close to the maximum value achieved in equilibrium CNO-nucleosynthesis (0.33). The combination of the high circumstellar mass (i.e., in the torus and an extended dust shell inferred from ISO far-infrared spectra) and the high ¹³C/¹²C ratio in I 22036 provides strong support for this object having evolved from a massive (≳4M _⊙) progenitor in which hot-bottom-burning has occurred.  相似文献   

论稳定电流场的入射、反射、透射间的关系          下载免费PDF全文

傅平 《地球物理学报》1994,37(1):108-114

根据分界面上稳定电流场的边界条件，解稳定电流场Ｌａｐｌａｃｅ方程，给出椭球形分界面入射场、反射场及透射场的表达式，并导出圆柱形、球形分界面上入射角、反射角及透射角的关系式后，指出，只在少数特殊情况下三者才相等，对一般形状的大多数光滑连续分界面情况，它们是不相等的．其值取决于分界面的具体形状．  相似文献