陕西省数字地震台下方壳幔速度结构研究   总被引：3，自引：1，他引：3  

张学民  刁桂苓  王为民  束沛镒 《华北地震科学》2005,23(2):1-9

利用广义反、透射系数的传递矩阵计算理论地震图，用快速模拟退火法搜索最佳模型，通过与地震台站实际记录的P波波形进行拟合对比，反演了陕西省13个数字地震台下方的P波速度结构。台站分布区域涉及到秦岭造山带、渭河盆地及鄂尔多斯地台三个构造区域。结果显示，3个构造区的地下速度结构差异明显，呈现了各自的构造特点。其中秦岭造山带上地壳乃至地表速度高，中下地壳出现多个低速层，可能与岩石脱水、构造滑脱带等有关；渭河盆地内上中地壳高低速度层交替出现，反映了断层活动在浅部的影响；鄂尔多斯地台有部分台站保持稳定的匀速构造。反映了古老地台地层稳定发展的特性，部分台站受到后期改造，低速层位增多。因为变化剧烈的台站分布在盆地的南部和西部。而且震源机制解显示该区主应力场方向为近东西向，可以说秦岭北缘的断裂作用以及后来来自青藏高原的挤压应力是导致渭河盆地形成和发展的主要因素。最后我们讨论了速度结构与强震、地震分布以及不同构造演化的关系。  相似文献   

Fault population investigation and estimating magnitude of extension in Guma Graben, Central Afar, Ethiopia     

Samson Tesfaye   《Journal of African Earth Sciences》2005,41(5):437-444

Extension in the Afar depression occurs on steeply dipping normal faults of many scales. An estimate for cumulative extension can be derived by summing the heave of these faults using digital topographic data, supplemented by field observations of fault dip. If it can be established that the distribution of faults exhibits self-similarity, an estimate of the contribution from faults too small to appear on the digital imagery can be incorporated into the integrated estimate for cumulative extension. A field study of faulting was undertaken within the Dobe and Guma grabens of Central Afar. A fractal dimension of 0.48 was obtained for the measured population of fault throws (n = 92) in 3 traverses totaling 42 km, a value interpreted to represent the dominant contribution to extension from faults with large throw. The local extension rate across Guma graben is estimated to be between 0.06 and 0.24 mm/year. The higher topographic position of the floor of Guma graben, relative to the sediment filled, adjacent floors of Dobe and Immino grabens is perhaps an indication of a slower rate of extension across Guma graben as compared to Dobe and Immino grabens, assuming they all initiated at the same time.  相似文献   

Low energy trajectories for the Moon-to-Earth space flight     

V. V. Ivashkin 《Journal of Earth System Science》2005,114(6):613-618

The Moon-to-Earth low energy trajectories of ‘detour’ type are found and studied within the frame of the Moon-Earth-Sun-particle system. These trajectories use a passive flight to the Earth from an initial elliptic selenocentric orbit with a high aposelenium. The Earth perturbation increases the particle selenocentric energy from a negative value first to zero and then to a positive one and therefore leads to a passive escape of the particle motion from the Moon attraction near the translunar libration pointL ₂. This results in the particle flight to a distance of about 1.5 million km from the Earth where the Sun gravitation decreases the particle orbit perigee distance to a small value that leads to the particle approaching the Earth vicinity in about 100 days of the flight. A set of the Moon-to-Earth ‘detour’ trajectories is defined numerically. Characteristics of these trajectories are presented. The ‘detour’ trajectories give essential economy of energy (about 150 m/s in Delta V) relative to the usual ones.  相似文献   

Luna-Glob project in the context of the past and present lunar exploration in Russia     

E. M. Galimov 《Journal of Earth System Science》2005,114(6):801-806

The Russian Luna-Glob project has been conceived with a view to understand the origin of the Earth-Moon system. The objectives and main features of the Luna-Glob mission, which will mainly study the internal structure of the Moon by seismic instruments, are described in the context of the past and current program of lunar exploration in Russia.  相似文献   

An analysis of near-circular lunar mapping orbits     

R. V. Ramanan  V. Adimurthy 《Journal of Earth System Science》2005,114(6):619-626

Numerical investigations have been carried out to analyse the evolution of lunar circular orbits and the influence of the higher order harmonics of the lunar gravity field. The aim is to select the appropriate near-circular orbit characteristics, which extend orbit life through passive orbit maintenance. The spherical harmonic terms that make major contributions to the orbital behaviour are identified through many case studies. It is found that for low circular orbits, the 7th and the 9th zonal harmonics have predominant effect in the case of orbits for which the evolution is stable and the life is longer, and also in the case of orbits for which the evolution is unstable and a crash takes place in a short duration. By analysing the contribution of the harmonic terms to the orbit behaviour, the appropriate near-circular orbit characteristics are identified.  相似文献   

广东梅县嵩溪早侏罗世火山活动及其地质构造与成矿意义   总被引：2，自引：0，他引：2  

郑庆年 《矿产与地质》1996,(2)

从熔岩——玄武岩的岩石学、岩石化学、微量元素、稀土元素和锶同位素组成，以及火山旋回中玻璃碎屑岩诸方面特征，详细地研究了下侏罗统含矿层位内海底基性火山活动，阐述矿区玄武岩形成环境为夭折的大陆裂谷前期地壳槽形裂陷地堑系——裂陷槽。并讨论该裂陷槽环境中基性火山活动的银锑成矿意义  相似文献   

Hydrogeological evolution of the Luni river basin,Rajasthan, western India: A review     

V. N. Bajpai 《Journal of Earth System Science》2004,113(3):427-451

The Luni river basin has been evolved as a result of typical hydrogeomorphic processes of arid zone, operating under the influence of active tectonic lineaments. A detailed analysis of stream morphology in relation to geology and lineaments carried out on selected windows indicated the morphological control of the streams while flowing over the lineaments from the eastern to the western part of the basin. Typical valley fills indicated by dark green tone on digitally processed images and the pediments showing greenish white tone appear in sharp contrast and indicate respectively the graben and horst structures. A detailed identification of lineaments for the georesources and geological evaluation has been carried out. Earlier analysis carried out on Bouguer anomalies correlate with graben and horst structures in the subsurface. Quaternary sequences have been dated from 80 ka to 3 ka indicating a range of fluvial to aeolian deposits reflecting prevailing climatic conditions. However, the changes in sediment type from coarse and mixed of all size grades to fine in a vertical litho-column warrant further studies on fine resolution stratigraphy and high resolution stratigraphy for understanding climatic variations in the region  相似文献   

半地堑式断陷盆地的油气成藏模式--以松辽盆地梨树断陷为例   总被引：8，自引：4，他引：8  

董清水  赵占银  刘招君  郭巍  黄湘通 《吉林大学学报(地球科学版)》2003,33(1):43-47

半地堑式断陷盆地是松辽盆地深部断陷的主要类型，是今后油气勘探重点。以梨树断陷为例，根据半地堑式断陷盆地的构造和层序地层发育特点，针对此类盆地的生储盖组合规律，总结出该类盆地中主要存在有滚动背斜油气藏、断层油气藏、超覆型上倾尖灭岩性油气藏、相变型上倾尖灭岩性油气藏、透镜型岩性油气藏、潜山油气藏等6种类型；探讨了半地堑式断陷盆地的油气成藏模式。  相似文献   

Analysis Method for Predicting Strain in Interior Beds and Sub-Resolution Faults from Area Balance Theory in Extensional Basins   总被引：1，自引：0，他引：1  

Groshong Jr R H 《中国地质大学学报(英文版)》2002,13(4)

Extensional basins include mainly grabens and half grabens displaced along a lower detachment. Based on area balance theory, there is a linear relationship between a height of regional and the lower detachment h on the outside of the basin and “lost area S“ from the regional in the basin. The pre-growth beds above lower detachment are of the same extensional displacement so that an “S-h diagram“ can be used to determine the depth to lower detachment and to calculate the total extensional displacement of the beds above the lower detachment. The extensional displacement is dominated by the heave of various scale normal faults. The displacement of obvious faults can be immediately figured out from the measured bed-length. The requisite extension calculated by area balance is the layer-parallel strain, which could be accommodated by displacement on sub-resolution faults. Accordingly, the layer-parallel strain can help us predict the magnitude and distribution of sub-resolution faults on the basis of analysis of the structural style and rheological behavior.  相似文献   

环月飞行器精密定轨的模拟仿真   总被引：11，自引：2，他引：11  

胡小工  黄珹  黄勇 《天文学报》2005,46(2):186-195

以中国正在实施的探月计划“嫦娥1号”工程为背景，分析了在中国联合S波段(USB)测控网和甚长基线射电干涉(VLBI)跟踪网的现有空间分布、观测精度水平下的环月飞行器精密定轨．采用的方法是模拟仿真计算，即首先模拟观测数据，然后在计入各误差源的影响后进行求解，并对解算结果进行比较．模拟仿真的工具是美国宇航局哥达德飞行中心的空间数据分析软件系统GEODYN．环月飞行的主要误差源是月球重力场，为此首先讨论了目前精度最高的月球重力场模型JGL165P1的(形式)误差．在模拟了测距、测速以及VLBI的时延、时延率数据后，计入月球重力场的误差进行精密轨道确定．定轨时采用了减缩动力学(reduced dynamic)方法，即选用合适的经验加速度参数吸收重力场误差对定轨的影响．结果表明对于一个不将月球重力场作为主要科学目标的探月计划(如“嫦娥1号”)，减缩动力学方法是一个简单、有效地提高环月飞行器定轨精度的方法．  相似文献