Acoustic wave attenuation in the gas hydrate-bearing sediments of Well GC955H,Gulf of Mexico     

Jiliang Wang  Shiguo Wu  Jianhua Geng  Priyank Jaiswal 《Marine Geophysical Researches》2018,39(4):509-522

A better understanding of wave attenuation in hydrate-bearing sediments is necessary for the improved geophysical quantification of marine gas hydrates. Here we compare the attenuation behavior of hydrate-saturated vs water-saturated sediments at site GC955H, in the Gulf of Mexico, which was surveyed during the JIP Leg II expedition. We compute the P-wave attenuation of the gas hydrate bearing sediments using the median frequency shift method on the monopole waveforms. The results show that P-wave attenuation due to low saturation (<?0.4) in hydrate-filled fractures of fine-grained sediment is comparable to that of the water-filled fracture case. On the contrary, P-wave attenuation due to high saturation (>?0.4) in the hydrate-filled pores of coarse-grained sediments can be up to as much as three times more than that of the water-saturated case. The correlation analysis shows that the P-wave attenuation increases with the increasing gas hydrate saturation for the highly saturated gas hydrate-bearing sand interval while the correlation of the P-wave attenuation and hydrate saturation is weak for low saturated gas hydrate-bearing shale interval. The results show that P-wave attenuation is more likely to be used as a geophysical proxy for gas hydrate quantification of highly concentrated coarse-grained sediment rather than for that of fine-grained sediment. To examine the P-wave behavior in sand, we use the improved LCAM model, which accounts for physical factors such as grain boundary roughness and squirt flow to explain the observed differences in P-wave attenuation between hydrate and water-saturated coarse-grained sediment. Our results provide further geophysical evidences for P-wave behavior in the gas hydrate-bearing sediments in the field.  相似文献   

森林火灾对典型小流域径流影响模拟          下载免费PDF全文

周艳春  张永强  许士国 《水科学进展》2013,24(2):190-196

以澳大利亚东南部Mcmahons Creek 流域1983年发生的森林火灾为例,运用AWRA-L和新安江模型模拟火灾后流域的基准径流过程,进而估算火灾对径流的影响。AWRA-L和新安江模型模拟结果表明,火灾发生后14年(1983—1997年)内流域产水量分别增加140 mm和123 mm,占火灾前(1974—1982年)年均径流量的33%和29%;火灾发生14年后的1998—2004年,增加量分别为43 mm和33 mm,占火灾前年均径流量的10%和8%。说明森林火灾引起短期内流域径流量的明显增加,随着植被的恢复流域产流增加量减少,森林砍伐是后期径流增加的重要原因。该研究对森林流域的水资源管理具有重要的参考价值。  相似文献   

Seismic characteristics and development of the Xisha carbonate platforms,northern margin of the South China Sea     

Ma Yubo  Wu Shiguo  Lv Fuliang  Dong Dongdong  Sun Qiliang  Lu Yintao  Gu Mingfeng 《Journal of Asian Earth Sciences》2011,40(3):770-783

The Xisha carbonate platforms, which include the modern-day Xisha Atoll, occur upon the northern continental margin of the South China Sea (SCS). In this study, we identify the seismic characteristics about various sedimentary facies of the carbonate platform and different types of reef in this area, based on the 2-D seismic data, reefs show high-amplitue moundy continuous reflection at the top and weak chaotic reflections inside. Carbonate platforms show high-amplitude continuous reflection at the top and high reflection alternative with weak reflection. The above analysis provided information about the influence of fluctuations in relative sea level, tectonic movements, paleotopography and the development mechanism of the carbonate platform. Based on the seismic data and data from drillholes (Xichen-1, Xiyong-1), we propose a schematic sedimentary model of the Xisha carbonate platforms at the northern margin of the SCS and outline five stages of development for the carbonate platform. Its sedimentary evolution consists of Initial establishment stage, development stage, exposure stage, drowning stage and large atoll reefs development stage. We also propose that several phases tectonisms supply proper environment and structural position for carbonate platform development, they can also destroyed the exist platforms. Besides, eustasy change was also the main influential factor on the development of the platforms.  相似文献   

A method combining numerical analysis and limit equilibrium theory to determine potential slip surfaces in soil slopes   总被引：1，自引：0，他引：1  

Shiguo Xiao  Liping Yan  Zhiqiang Cheng 《山地科学学报》2011,8(5):718-727

This paper describes a precise method combining numerical analysis and limit equilibrium theory to determine potential slip surfaces in soil slopes. In this method, the direction of the critical slip surface at any point in a slope is determined using the Coulomb’s strength principle and the extremum principle based on the ratio of the shear strength to the shear stress at that point. The ratio, which is considered as an analysis index, can be computed once the stress field of the soil slope is obtained. The critical slip direction at any point in the slope must be the tangential direction of a potential slip surface passing through the point. Therefore, starting from a point on the top of the slope surface or on the horizontal segment outside the slope toe, the increment with a small distance into the slope is used to choose another point and the corresponding slip direction at the point is computed. Connecting all the points used in the computation forms a potential slip surface exiting at the starting point. Then the factor of safety for any potential slip surface can be computed using limit equilibrium method like Spencer method. After factors of safety for all the potential slip surfaces are obtained, the minimum one is the factor of safety for the slope and the corresponding potential slip surface is the critical slip surface of the slope. The proposed method does not need to pre-assume the shape of potential slip surfaces. Thus it is suitable for any shape of slip surfaces. Moreover the method is very simple to be applied. Examples are presented in this paper to illustrate the feasibility of the proposed method programmed in ANSYS software by macro commands.  相似文献   

A Method Combining Numerical Analysis and Limit Equilibrium Theory to Determine Potential Slip Surfaces in Soil Slopes     

XIAO Shiguo  YAN Liping  CHENG Zhiqiang 《山地科学学报》2011,(5)

This paper describes a precise method combining numerical analysis and limit equilibrium theory to determine potential slip surfaces in soil slopes. In this method, the direction of the critical slip surface at any point in a slope is determined using the Coulomb’s strength principle and the extremum principle based on the ratio of the shear strength to the shear stress at that point. The ratio, which is considered as an analysis index, can be computed once the stress field of the soil slope is obtained. Th...  相似文献   

Tectonic Evolution of the Wanan Basin,Southwestern South China Sea     

Lü Caili  ZHANG Gongcheng  YAO Yongjian  WU Shiguo 《《地质学报》英文版》2014,88(4):1120-1130

Quantitative studies on the extension and subsidence of the Wanan Basin were carried out based on available seismic and borehole data together with regional geological data.Using balanced cross-section and backstripping techniques,we reconstructed the stratigraphic deposition and tectonic evolution histories of the basin.The basin formed from the Eocene and was generally in an extensional/transtensional state except for the Late Miocene local compressoin.The major basin extension ocurred in the Oligocene and Early Miocene(before ~16.3 Ma) and thereafter uniform stretch in a smaller rate.The northern and middle basin extended intensely earlier during 38.6–23.3 Ma,while the southern basin was mainly stretched during 23.3–16.3 Ma.The basin formation and development are related to alternating sinistral to dextral strike-slip motions along the Wanan Fault Zone.The dominant dynamics may be caused by the seafloor spreading of the South China Sea and the its peripheral plate interaction.The basin tectonic evolution is divided into five phases:initial rifting,main rifting,rift-drift transition,structural inversion,and thermal subsidence.  相似文献   

Late Cenozoic Tectonic Deformation in the Dongsha Islands and Adjacent Sea Area   总被引：3，自引：0，他引：3  

吴时国  刘展  王万银  郭军华  T.Lüdmann  H.K.Wong 《中国海洋湖沼学报》2003,21(4):377-388

Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magnetic and drilling wells data led to the discovery of three post-fault sequences (Ⅴ, Ⅵ, Ⅶ). Extensive tectonic uplift, magma activity and erosion occurred in Dongsha Island and the adjacent area, where most of the faults in the northeastern SCS were still active during Pliocene and Quaternary. Two groups of faults trending NEE and NW were developed during Late Cenozoic. We conclude that three important tectonic movements, especially Dongsha movement(4.4 - 5.2 Ma) and Liuhua movement (1.4 - 1.89 Ma), controlled the structural framework in the Dongsha rise; whose deformation in the east is stronger than that in the west and whose stress field variation suggests that the tectonic uplift in the study area contributed to magmato-tectonic events correlated to the main collision phases between the East China and Taiwan 5 - 3 and 3 - 0 Ma ago.  相似文献   

哈达湾老工业区监测浅析     

石海燕  申世国 《测绘与空间地理信息》2021,44(9):137-139

采用国情监测理论与方法,结合统计学原理,利用吉林省吉林市哈达湾老工业区改造前2010年和改造中2017年两期的地上建筑物变化、用地性质变化、绿地变化、空气污染变化等情况的监测结果,开展综合统计分析,客观评价哈达湾老工业区搬迁改造实施的成效.对哈达湾老工业区现状进行全面具体评估,为未来的城市建设与政府决策提供很好的支撑,成为国情监测在实际应用上的典例,为哈达湾老工业区搬迁改造持续进行提供了有力的支持.  相似文献   

Sedimentary processes in Zenisu deep-sea channel revealed by side-scan imagery     

吴时国  郭军华TOKUYAMA Hidekazu 《中国海洋湖沼学报》2005,23(4):368-375

1 INTRODUCTIONThe eastern Nankai Trough is a submarinetrench reflecting subduction zone where the earth'soceanic crust plunges beneath Japan Islands andcharacterized by extreme topographic relief (Fig.1).The convergent margin off Japan is characterizedmorphologically by numerous deep sea channels(such as the Nankai channel and Zenisu channel),which are closely related to the subduction proc-esses. Channel systems are considered to represent adistinct deep water sedimentation environmen…  相似文献   

琼东南陆坡深水水道主控因素及勘探应用   总被引：3，自引：0，他引：3  

袁圣强  吴时国  姚根顺 《海洋地质与第四纪地质》2010,(2)

结合全球海平面变化、气候变化、物源供给特征和地形条件,深入地分析和研究了发育在琼东南盆地陆坡区上新世和更新世地层中水道的形成主控因素及其在深水油气勘探中的应用价值和前景。提出琼东南陆坡上新世水道的主要因素是物源供给,包括来自红河和海南岛的物源,构造活动是关键诱发因素,上新世早期莺歌海盆地发育的大规模滑塌体与该水道的形成关系密切;给出更新世水道形成模式,其形成与第四纪冰期海平面的大幅度下降有关,地震活动诱发了中南半岛的小型山脉河流复苏,并对南海西部陆坡直接供给形成了该期水道。深水水道对于全球海平面变化、陆坡区物源供给情况和陆坡层序界面具有指示作用,并可作为良好的深水油气勘探目标,具有重要的深水油气勘探意义。  相似文献