汤加-克马德克海沟俯冲板块挠曲变形与板块弱化

We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench. Inversions were conducted to obtain best-fitting solutions of trench-axis loadings and variations in the effective elastic plate thickness for the analyzed flexural bending profiles. Results of the analyses revealed significant along-trench variations in plate flexural bending: the trench relief(W_0) of 1.9 to 5.1 km;trench-axis vertical loading(V_0) of –0.5×(10)~(12) to 2.2×(10)~(12) N/m; axial bending moment(M_0) of 0.1×(10)~(17) to 2.2×(10)~(17) N;effective elastic plate thickness seaward of the outer-rise region(T_e~M) of 20 to 65 km, trench-ward of the outer-rise(T_e~m) of 11 to 33 km, and the transition distance(X_r) of 20 to 95 km. The Horizon Deep, the second greatest trench depth in the world, has the greatest trench relief(W_0 of 5.1 km) and trench-axis loading(V_0 of 2.2×(10)~(12) N/m); these values are only slightly smaller than that of the Challenger Deep(W_0 of 5.7 km and V_0 of 2.9×(10)~(12) N/m) and similar to that of the Sirena Deep(W_0 of 5.2 km and V_0 of 2.0×(10)~(12) N/m) of the Mariana Trench,suggesting that these deeps are linked to great flexural bending of the subducting plates. Analyses using three independent methods, i.e., the T_e~M/T_e~m inversion, the flexural curvature/yield strength envelope analysis, and the elasto-plastic bending model with normal faults, all yielded similar average Te reduction of 28%–36% and average Te reduction area S￠Te of 1 195–1 402 km~2 near the trench axis. The calculated brittle yield zone depth from the flexural curvature/yield strength envelope analysis is also consistent with the distribution of the observed normal faulting earthquakes. Comparisons of the Manila, Philippine, Tonga-Kermadec, Japan, and Mariana Trenches revealed that the average values of T_e~M and T_e~m both in general increase with the subducting plate age.     

太平洋深海细菌多样性研究进展

深海是指深度在1,000m以下的大洋,从打破深海中没有生命的定论开始,在具有低温、高压、永久黑暗、营养贫乏等特征的深海环境中含有的大量细菌一直以来都是研究的重点对象之一。太平洋作为地球上最大的大洋,人们对其深海细菌的研究从起初的菌种多样性逐步延伸到功能多样性,包括在生态环境中参与的物质循环和能量流动以及代谢产物的功能应用性研究。深海中丰富的菌种资源不仅被应用到生态环境的防治与保护,同时也是酶制剂和药物来源的巨大宝库。太平洋地区的马里亚纳海沟作为地球的最深处,对此区域的研究,不仅可以丰富菌种多样性,更能开发新的菌种应用资源。本文就以上几个方面进行综述,深度整合目前太平洋深海细菌多样性的研究现状。     

郯庐断裂带中段安丘—莒县断裂淮河—女山湖段几何展布

郯庐断裂带中段最新活动的安丘—莒县断裂(命名为F5断裂)为中国东部地区重要的地震活动断裂。已有研究表明,F5断裂向南已延伸进入安徽境内的淮河—女山湖之间,但该段的具体几何展布还存在以下问题未解决：一是F5断裂以东的紫阳山东侧断裂是否属于F5断裂分支;二是F5断裂向南是否延伸至女山湖北岸。为解决以上问题,本次工作基于遥感解译、地质地貌调查、探槽开挖及断错地层年代样品测试等方法,对紫阳山东侧断裂及女山湖北岸一带断裂开展了研究。结果表明,紫阳山东侧断裂发育时代较老,在早、中更新世发生过强烈逆冲挤压运动,晚第四纪以来不活动,该断裂不属于F5断裂分支;郯庐断裂带在女山湖北岸上詹村一带断错了晚更新世地层,该处断裂为F5断裂向南的延伸部分;F5断裂已完全贯穿于淮河—女山湖之间,断层迹线单一、连续,段落总长度约20 km。文中还讨论了F5断裂向南应该终止于女山湖至明光市一带,断裂终止受区域古老构造格局控制,表明该断裂既有新生性又有继承性。     

Morphology and tectonics of the Yap Trench

We conducted swath bathymetry and gravity surveys the whole-length of the Yap Trench, lying on the southeastern boundary of the Philippine Sea Plate. These surveys provided a detailed morphology and substantial insight into the tectonics of this area subsequent the Caroline Ridge colliding with this trench. Horst and graben structures and other indications of normal faulting were observed in the sea-ward trench seafloor, suggesting bending of the subducting oceanic plate. Major two slope breaks were commonly observed in the arc-ward trench slope. The origin of these slope breaks is thought to be thrust faults and lithological boundaries. No flat lying layered sediments were found in the trench axis. These morphological characteristics suggest that the trench is tectonically active and that subduction is presently occurring. Negative peaks of Bouguer anomalies were observed over the arc-ward trench slope. This indicates that the crust is thickest beneath the arc-ward trench slope because the crustal layers on the convergent two plates overlap. Bouguer gravity anomalies over the northern portion of the Yap Arc are positive. These gravity signals show that the Yap Arc is uplifted by dynamic force, even though dense crustal layers underlie the arc. This overlying high density arc possibly forces the trench to have great water depths of nearly 9000 m. We propose a tectonic evolution of the trench. Subduction along the Yap Trench has continued with very slow rates of convergence, although the cessation of volcanism at the Yap Arc was contemporaneous with collision of the Caroline Ridge. The Yap Trench migrated westward with respect to the Philippine Sea Plate after collision, then consumption of the volcanic arc crust occurred, caused by tectonic erosion, and the distance between the arc and the trench consequently narrowed. Lower crustal sections of the Philippine Sea Plate were exposed on the arc-ward trench slope by overthrusting. Intense shearing caused deformation of the accumulated rocks, resulting in their metamorphism in the Yap Arc.     

浅谈岸线蚀退与保滩促淤

简要介绍了海岸线蚀退对胜利油田的危害,分析了海岸线蚀退的主要原因,提出应进行重点研究的内容,并提供了几种潜堤的结构型式。     

飞雁滩油田保滩促淤先导试验研究

介绍和分析了飞雁滩油田保滩促淤先导试验工程中采用的倒“T”形潜堤结构、初期破坏原因及相应加固措施,初步探讨了潜堤的保滩促淤效果和淤积速率,并对潜堤顶高程设计提出了建议。     

Linear wave reflection by trench with various shapes

Two types of analytical solutions for waves propagating over an asymmetric trench are derived. One is a long-wave solution and the other is a mild-slope solution, which is applicable to deeper water. The water depth inside the trench varies in proportion to a power of the distance from the center of the trench (which is the deepest water depth point and the origin of x-coordinate in this study). The mild-slope equation is transformed into a second-order ordinary differential equation with variable coefficients based on the longwave assumption [Hunt's, 1979. Direct solution of wave dispersion equation. Journal of Waterway, Port, Coast. and Ocean Engineering 105, 457–459] as approximate solution for wave dispersion. The analytical solutions are then obtained by using the power series technique. The analytical solutions are compared with the numerical solution of the hyperbolic mild-slope equations. After obtaining the analytical solutions under various conditions, the results are analyzed.     

Determining the circulation depth of thermal springs in the southern Rocky Mountain Trench, south-eastern British Columbia, Canada using geothermometry and borehole temperature logs

Geochemical data for thermal spring waters along the southern Rocky Mountain Trench in British Columbia, Canada were examined. The range of equilibration temperatures for the thermal springs is between 24 and 59°C, assuming that there is minimal mixing with colder shallow waters that might lead to a lowering of the calculated equilibration temperature. The chalcedony geothermometer is found to be the most appropriate given the carbonate host rocks. Temperature logs from 11 boreholes in the vicinity were used to calculate representative geothermal gradients, which range from 23.8 to 55.7°C/km with an average of 24.8±8.0°C/km. Using the average gradient and the range of equilibration temperatures calculated for each spring, the minimum range for the depth of origin of the thermal waters is 0.9–2.2 km. Heat flow values range from 90.3 to 155 mW/m², with an average of 109.1±21.0 mW/m². The moderate to high heat flow and heat generation result in generally higher temperatures at shallow depths, thus offering an explanation for the occurrence of thermal springs. The alignment of the thermal springs likely relates to the preferred northwest–southeast orientation for major thrust faults along the Rocky Mountain Trench, and with waters routed from depth along deep faults.

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Resumen Se examinan datos geoquímicos de aguas de fuentes termales a lo largo de la Trinchera sur de las Montañas Rocosas en Columbia Británica, Canadá. El rango de temperaturas de equilibrio para las fuentes termales se encuentra entre 24 y 59°C, asumiendo que existe mezcla mínima con aguas someras más frías que podrían conducir a un descenso de la temperatura de equilibrio calculada. El geotermómetro de calcedonia se ha encontrado que es el más apropiado debido a las rocas encajonantes carbonatadas. Se utilizaron los registros de temperatura de 11 pozos de la zona para calcular gradientes geotermales representativos, los cuales varían de 23.8 a 55.7°C/km con un promedio de 24.8±8.0°C/km. Utilizando el gradiente promedio y el rango de temperaturas de equilibrio calculadas para cada manantial, se estimó que el rango mínimo para la profundidad de origen de las aguas termales varía de 0.9 a 2.2 km. Los valores de flujo de calor varían de 90.3 a 155 mW/m², con un promedio de 109.1±21.0 mW/m². El flujo de calor moderado a alto y la generación de calor resultan en temperaturas generalmente más altas a profundidades someras ofreciendo de este modo una explicación para la ocurrencia de fuentes termales. El alineamiento de fuentes termales posiblemente se relaciona con la orientación preferida noroeste-sureste de fallas inversas principales a lo largo de la Trinchera de las Montañas Rocosas, y con aguas ascendentes profundas que se mueven a lo largo de fallas profundas.

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Résumé Les données géothermiques de sources thermales le long de la partie sud du fossé des Montagnes Rocheuses en Colombie Britannique, Canada, sont étudiées. Léchelle des températures déquilibre des sources thermales se situe entre 24 et 59°C, en assumant quil y a un mélange minimum avec les eaux froides de surface, ce qui conduit à une sous-évaluation de la température déquilibre. La calcédoine apparaît être le géothermomètre le plus approprié vu les roches hôtes carbonatées. Les diagraphies de température provenant de 11 forages proches ont été utilisées pour calculer le gradient géothermique représentatif, gradient compris entre 23.8 et 55.7°/km avec une moyenne de 24.8°/km. En utilisant le gradient moyen et les valeurs de température déquilibre calculées pour chaque source, la profondeur minimum des eaux thermales se situerait entre 0.9 et 2.2 km. Les flux de chaleur sont évalués entre 90.3 et 155 mW/m, avec une moyenne de 109.1±21.0 mW/m. Le transfert moyen de chaleur et la génération de chaleur résulte en températures ordinairement plus élevées aux faibles profondeurs, qui ainsi offre une explication à loccurrence de sources thermales. Les alignements de sources thermales sont vraisemblablement en relation avec lorientation Nord-Sud des principales failles-vraies le long du fossé des Montagnes Rocheuses, et avec lécoulement des eaux des profondeurs le long des failles.

     

马尼拉俯冲带缺失中深源地震成因初探

马尼拉俯冲带是整个南海地震活动多发区,地震成因与南海的形成和构造演化关系密切.对马尼拉俯冲带地震数据和层析成像结果进行了深入分析.结果表明:马尼拉俯冲带的地震活动主要为密集的浅源地震,缺失中深源地震.进一步分析揭示:①脱水和榴辉岩的形成在南海洋壳到达软流圈前就基本停止.马尼拉俯冲带南部在较浅的深度就转变为塑性变形,并停...