Geomorphological study on a clastic accretionary prism: The Nankai Trough     

Kyoko  Okino Yukihiro  Kato 《Island Arc》1995,4(3):182-198

Abstract The Nankai Trough, off southwest Japan, is one of the best sites for the study of geomorphic characteristics of a clastic accretionary prism. A recent multibeam survey over the central and eastern parts of the Nankai accretionary prism has revealed a large variation of the topography along the trough axis. Analysis of the bathymetric data suggests the existence of prism deformational features of different scales, such as depressions, embayment structures and cusps. These structures are the results of slope instability caused by basement relief of subducted oceanic plate. Unstable slopes recover by new accretion and development of a low angle thrust. Small-scale deformation due to the subduction of a small isolated seamount is then adjusted to the regional trend. By contrast, a 30 km indentation of the wedge observed in the eastern part of the Nankai Trough, the Tenryu Cusp, has seemed to retain its geometry. The subducted Philippine Sea plate has deformed greatly near the eastern end of the Nankai Trough, because of the collision between the Izu-Ogasawara (Bonin) arc and central Japan. Therefore, the indentation may be the result of the continuous subduction of a basement high, such as the Zenisu Ridge, which has been formed under north-south compression due to the arc-arc collision.  相似文献   

频谱成像技术在稠油热采地震监测中的应用   总被引：2，自引：0，他引：2  

王新红 《华北地震科学》2005,23(3):1-8

频谱成像技术可有效的描述地质反射层厚度的非连续性和岩性的非均质性,其在理论上主要是依据薄层反射的调谐原理,过去通常采用以离散傅里叶变换为基础的算法,但是,该方法存在着明显的局限性,因为估算的地震振幅谱的重要特征是所选时窗长度的函数.如果所选时窗过短,振幅谱会与变换窗函数褶积,失去频率的局部化特征,而且过短的时窗会使子波的旁瓣呈现为单一反射的假象.增加时窗长度,会改善频率的分辨率.但如果所选时窗过长,时窗内的多个反射会使振幅谱以槽痕为特征,很难分清单个反射的振幅谱特征.由于在实际运用中,以傅里叶变换相关的算法的时窗问题,难以选择好时窗长度,而且无法定量分析时窗长度产生的偏差,因而会使振幅谱的估算产生偏差.以小波变换为基础的时频分析技术成了非平稳性信号的重要分析工具,在很多实际应用中已取代了傅里叶变换的分析方法.以小波变换为基础的瞬时谱分析技术能得到精确的时频分析结果,同时避免了时窗问题.它反映出了储层在纵向上时间及厚度上变化情况和横向上的地质不连续性的信息,因此能使解释人员快速而有效地描述储层特征的空间变化.  相似文献   

The geomorphological significance of airflow patterns in transverse dune interdunes   总被引：1，自引：0，他引：1  

M.C. Baddock  I. Livingstone  G.F.S. Wiggs   《Geomorphology》2007,87(4):322-336

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Biodiversity conservation and pastoralism—reducing herd size in a communal livestock production system in Richtersveld National Park     

H.H. Hendricks  W.J. Bond  J.J. Midgley  P.A. Novellie 《Journal of Arid Environments》2007,70(4):718

Biodiversity is a critical component of the natural environment and the protection of it often meant the displacement of local communities in developing countries. The Richtersveld National Park (South Africa) is unusual in that it forms part of the Richtersveld communal rangeland and is currently managed for goat and sheep farming as well as biodiversity conservation under a contractual agreement. These two objectives are not regarded as mutually compatible and have created tension between conservation management officials and pastoralists. We set out to examine the consequences of reducing herd size in a communal livestock production system in support of biodiversity conservation in a protected area. Kidding, animal offtake (sales and slaughter), mortality and herd persistence showed no clear incentives for an individual pastoralist to reduce herd size. Reducing herd size is not considered a recommended intervention for the conservation of biodiversity or livelihood improvement of pastoralists in the park. The future of the natural resources of the national park is dependent on a delicate balance between the needs of the pastoralists and the conservation of those very same resources that the pastoralists use.  相似文献   

下二门油田H2Ⅲ油组交联聚合物驱后油藏剩余油分布特征     

胡云亭  杨永利  关振良  张磊 《地质科技情报》2007,26(3):47-50

微观驱油试验表明,交联聚合物驱后剩余油进一步减少,主要以斑块状、小油滴状等形态分布于微孔隙中;数值模拟显示,下二门油田H2Ⅲ油组交联聚合物驱后80.8%的面积已为中强水淹,纵向上79.7%的剩余油分布于主力油层.受构造、储层物性及井网因素控制,未淹、弱水淹剩余油平面上主要分布在断层附近、断层破碎带、微构造高点和砂体上倾尖灭区等部位;纵向上主要分布于低渗透层段.针对剩余油分布特征,通过完善注采关系、优化注采结构,单元含水量的上升速度和产量递减幅度得到控制,采收率在交联聚合物驱的基础上进一步提高了2.01%.  相似文献   

Analysis of radial movement of an unconfined leaky aquifer due to well pumping and injection   总被引：1，自引：0，他引：1  

Jiang Li 《Hydrogeology Journal》2007,15(6):1063-1076

Radial movement of an unconfined leaky aquifer was studied with respect to hydraulic forces that are induced by well recharge and discharge. New analytic solutions in the velocity and displacement fields were found and applied to describe transient movement in an unconfined leaky aquifer. Linear momentum and mass balance of saturated porous sediments, the Darcy-Gersevanov law, and the analytic solution of hydraulic drawdown for unsteady flow within the unconfined leaky aquifer were introduced to find the new solutions. Analytic results indicate that the nonlinear relation between the initial hydraulic head (h₀) and the well function has an insignificant effect on the aquifer transient movement when the drawdown s<0.02h ₀. When the well function is simplified with different assumptions and pumping conditions, the new solutions correspondingly reduce to cases that are similar to the Hantush-Jacob, Muskat, and Theis transient movement of a confined leaky aquifer. It was found that large leakance is important in slowing radial movement and reducing aquifer deformation. Flow velocity in the aquifer is more responsive to leakance than to cumulative displacement within the aquifer. The zones and boundary with tensile stress can be located using the same approach applied to a confined aquifer for risk assessment of earth fissuring.

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Résumé Le mouvement radial dans un aquifère semi-perméable libre a été étudié en considérant les forces hydrauliques induites par la recharge et le prélèvement au niveau d’un puits. De nouvelles solutions analytiques des champs de vitesse et de déplacement ont été trouvées et appliquées pour décrire le mouvement transitoire dans un aquifère semi-perméable libre. Pour trouver les nouvelles solutions, le moment linéaire et le bilan de masse dans les sédiments poreux saturés, la loi de Darcy-Gersevanov, et la solution analytique du rabattement hydraulique pour un écoulement transitoire dans un aquifère semi-perméable libre sont pris en compte. Les résultats analytiques montrent que la relation non-linéaire entre le potentiel hydraulique initial (h₀) et la fonction de puits a un effet insignifiant sur le mouvement transitoire de l’aquifère quand le rabattements s <0.02h₀. Si la fonction de puits est simplifiée en tenant compte de différentes hypothèses et conditions de pompage, les nouvelles solutions se réduisent en conséquence à des cas similaires au mouvement transitoire dans un aquifère semi-perméable captif selon Hantush-Jacob, Muskat, et Theis. Il s’est avéré qu’une drainance élevée est importante pour le ralentissement du mouvement radial et la réduction de la déformation de l’aquifère. La vitesse d’écoulement dans l’aquifère est plus sensible à la drainance qu’au déplacement cumulé dans l’aquifère. Les zones et la frontière présentant des contraintes de traction peuvent être localisées en utilisant la même approche appliquée à un aquifère captif pour l’évaluation des risques de fissuration du sol.

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Resumen Se ha estudiado el movimiento radial en un acuífero no confinado con fuga en relación a las fuerzas hidráulicas que son inducidas por la descarga y recarga del pozo. Se encontraron nuevas soluciones analíticas en los campos de desplazamiento y velocidad, las cuales se aplicaron para describir el movimiento transitorio en un acuífero no confinado con fuga. Se han introducido cálculos de balance de masa y momentum lineal de los sedimentos porosos saturados, la Ley Darcy-Gersevanov, y la solución analítica de descenso hidráulico para flujo sin régimen permanente dentro del acuífero no confinado con goteo para encontrar las nuevas soluciones. Los resultados analíticos indican que la relación no lineal entre la presión hidráulica inicial (h₀) y la función del pozo tiene efecto insignificante en el movimiento transitorio del acuífero cuando el descenso s < 0.02h₀. Cuando se simplifica la función del pozo en base a diferentes supuestos y condiciones de bombeo se reducen las nuevas soluciones a casos que son similares a el movimiento transitorio Hantush-Jacob, Muskat, y Theis de un acuífero confinado con goteo. Se encontró que las fugas grandes son importantes en la disminución del movimiento radial y en la reducción de la deformación del acuífero. La velocidad de flujo en el acuífero responde más a las fugas que al desplazamiento acumulativo dentro del acuífero. Pueden localizarse zonas y límites con esfuerzos tensionales usando el mismo enfoque aplicado a acuíferos confinados para evaluación de riesgo de generación de fracturas en el terreno.

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振幅处理技术在探地雷达资料处理中的应用   总被引：4，自引：1，他引：4  

李成方  王绪本  王山山 《物探化探计算技术》2002,24(3):224-227

作者在文中简述了在自激自收（10天线距）的探地雷达资料处理中，振幅处理（振幅恢复、道内振幅平衡）和道间振幅均衡的方法原理。在实现编程后，应用于实际资料处理，用以增强雷达的深部弱信号，平衡道内的振幅能量和滤除干扰噪声，取得了良好的效果。  相似文献   

山西沁水煤层气田采收率预测   总被引：1，自引：0，他引：1  

拜文华  赵庆波  刘锐娥 《现代地质》2001,15(4):438-444

采用地质类比、等温吸附曲线及储层数值模拟 3种方法对山西沁水煤层气田主力气层———二叠系山西组 3# 煤层、石炭系太原组 15 # 煤层的煤层气采收率进行了预测 ,结果 3# 煤层的煤层气采收率为 6 2 % ,15 # 煤层的采收率为 5 5 % ,总平均采收率为 5 9%。分析对比了这 3种方法的运用条件及优缺点 ,指出煤层气采收率的预测必须采用多种方法 ,并结合具体的煤层气地质特点进行综合分析 ,才能得出合理的结论。  相似文献   

Empirical predictors of annual bed load travel distance,and implications for salmonid habitat restoration and protection     

Timothy J. Beechie 《地球表面变化过程与地形》2001,26(9):1025-1034

Measurements of annual travel distance (L_b) of bed load sediment at 16 locations in Alaska, the intermountain USA, west coast USA and Scotland are strongly correlated with bankfull channel width (r² = 0·86, p < 0·001). Travel distance of particles is probably limited by trapping in bars, which have a longitudinal spacing proportional to channel width. Increased abundance of woody debris reduces bar spacing and may reduce L_b. Longer cumulative duration of bed load transporting flows in a year appears to increase L_b. Other predictors of annual travel distance such as stream power per unit length, drainage area and bankfull discharge were less well correlated with L_b (r² ranging from 0·27 to 0·51). Stream power per unit bed area, basal shear stress and slope were not significantly related to L_b (r² < 0·05). Most correlations were improved when regressions were limited to data from the west coast USA. Travel distance estimates can be used to help identify reaches that may take longer to recover from large, short‐term increases in sediment supply. Published in 2001 by John Wiley & Sons, Ltd.  相似文献   

胡状集构造地层古厚度的恢复及其意义     

关振良  崔武林 《地球科学》1992,17(1):39-44

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