Trench effects on lateral p-y relations for pipelines embedded in stiff soils and rocks     

《Computers and Geotechnics》2017

Existing relationships for lateral backfill pressures on pipelines assume that the trench is adequately wide to contain the failure surface. This condition is commonly violated in design and construction practice, putting at risk the pipeline safety. In this context, size and shape effects for trenches excavated in stiff soils and rocks, are numerically investigated, through experimentally-calibrated parametric analyses. It is shown that, for narrow trenches, ultimate pressures and yield displacements may increase up to an order of magnitude compared to “infinite-trench” values, while excavation of inclined walls reduces the above detrimental effects. Simplified relations are developed to aid pipeline design.  相似文献   

First report of sablefish in spawning condition off the coast of Kamchatka and the Kuril Islands     

Orlov  Alexei M.; Biryukov  Igor A. 《ICES Journal of Marine Science》2005,62(5):1016-1020

  相似文献   

Seismic imaging of the entire arc of Tohoku and Hokkaido in Japan using P-wave, S-wave and sP depth-phase data   总被引：3，自引：0，他引：3  

Zhi Wang  Dapeng Zhao 《Physics of the Earth and Planetary Interiors》2005,152(3):144-162

In order to better understand seismic structure and seismotectonics of the entire arc of Tohoku and Hokkaido in Japan, we combined arrival time data from earthquakes beneath Tohoku and Hokkaido land areas, and beneath the Pacific Ocean to determine the three-dimensional (3D) velocity structures (Vp and Vs) under the entire Northeast (NE) Japan-Kuril arc. We adopted 176,431 P-wave and 110,953 S-wave arrival times, from 5123 local earthquakes, and 2843 sP depth-phase data from 385 events that occurred beneath the Pacific Ocean. The 385 suboceanic events were accurately relocated by using P-wave, S-wave and sP depth-phase arrival time data jointly. The obtained results confirmed the major features delineated by previous studies and revealed some new features of the structural heterogeneity beneath NE Japan and the Kuril forearcs. High-velocity anomalies of the cold subducting Pacific slab and low-velocity anomalies in the hot mantle wedge were imaged clearly. Strong lateral heterogeneities were revealed on the upper boundary of the Pacific slab under the forearc region, which showed a good correlation with the spatial distribution of large interplate earthquakes. These results indicated that strong coupling sections (or asperities) and weak-coupled or decoupled patches might exist along the upper boundary of the Pacific slab. Widespread low-velocity anomalies were visible in the forearc mantle above the subducting Pacific slab, which might reflect serpentinization of the forearc mantle associated with the dehydration process of the subducting slab. Our results also showed a general tendency for seismic coupling in the asperities to be located around low-velocity areas on the slab boundary under the suboceanic region.  相似文献   

Variable microstructure of peridotite samples from the southern Mariana Trench: Evidence of a complex tectonic evolution   总被引：2，自引：0，他引：2  

Katsuyoshi Michibayashi  Miki Tasaka  Yasuhiko Ohara  Teruaki Ishii  Atsushi Okamoto  Patricia Fryer 《Tectonophysics》2007,444(1-4):111-118

We retrieved samples of peridotite from a dredge haul (KH92-1-D2) collected during Cruise KH92-1 undertaken by the research vessel (R/V) Hakuho in 1992 at the landward trench slope of the southern Mariana Trench (11°41.16′N, 143°29.62′E; depth 6594–7431 m), which is the deepest ocean in the world. Ten of 30 retrieved samples possessed both a foliation and lineation, as assessed from 46 thin sections of various orientations and observations of hand samples. The samples showed marked variation in microstructure, ranging from coarse (> 5 mm) equigranular and intensely elongated textures to finer (< 1 mm) porphyroclastic and fine-grained equigranular textures. Olivine fabrics also varied among the different samples, with (010)[100] and (010)[001] patterns (termed A- and B-type, respectively) observed in samples with coarse textures and no clear patterns observed in samples with fine textures. Even though the peridotite samples were retrieved from a single dredge site, some contain primary tectonic microstructures and some contain secondary microstructures. Recent bathymetric and topographic analyses indicate that the lithosphere in this region is as thin as 20 km. Such a thin lithosphere may have been intensely deformed, even perhaps in the ductile regime, during fore-arc extension; consequently, the observed variations in microstructure within the peridotite samples probably reflect the complex tectonic evolution of the southern Mariana region.  相似文献   

罗山东麓断裂全新世古地震研究   总被引：5，自引：0，他引：5  

闵伟  柴炽章  王萍  杨平 《高原地震》1993,(4)

罗山东麓断裂全新世活动强烈,古地震现象丰富。探槽揭露出晚更新世末或全新世初以来,已发生过5次7级左右的古地震事件,除最早的一次时间不明外,其它4次分别发生在距今约8400年、5400—5020年、3900年和2260年。全新世早期古地震重复间隔在3000年左右,晚期为1500年左右。  相似文献   

Geodynamics of the Amirante Ridge and Trench Complex,Western Indian Ocean     

《International Geology Review》2012,54(1):81-92

The formation and evolution of the ～600 km long arcuate Amirante Ridge and Trench Complex (ARTC) is a significant geomorphic–structural feature in the Western Indian Ocean (WIO). The WIO contains evidence of at least two major magmatic episodes followed by continental rifting within the span of a little more than 20 million years. This involved the splitting of Madagascar from India at around 85 Ma and then separation between India and the Seychelles at 64–63 Ma as a possible consequence of two powerful volcanic eruptions from the Marion and Reunion hot spots, respectively. Formation and evolution of the ARTC represents this tumultuous period in the Indian Ocean, approximately between 85 and 60 Ma (Late Cretaceous–Early Tertiary).

We integrated geophysical, palaeomagnetical, and petrological data to examine three existing models that attempt to explain the formation of ARTC. In contrast, our study hints at several stages of extension and compression responsible for its formation. Our integrated data also suggest that the Carlsberg Ridge may have played a prominent role in the evolution of the ARTC that seems to have formed through a ridge-jump process after the conjugate spreading centres – Mascarene and Palitana ridges formed earlier during the India–Madagascar separation – ceased spreading because of violent eruption of the Reunion hot spot at around 65 Ma. The eruption disturbed the plumbing system of magma ascent, resulting in cessation of spreading along the conjugate spreading centres, forcing a ridge jump.

A collage of seismic refraction and reflection, free-air gravity, magnetic anomaly data, and Ar dating of rocks indicates that as the Carlsberg Ridge swept the Seychelles towards south, the crust between Madagascar and the Seychelles was increasingly compressed, with the abandoned northern Mascarene spreading centre absorbing the maximum stress. With continued compression, the western limb of the abandoned spreading ridge was thrust below the eastern limb to a limited degree. This partial subduction agrees with the gravity and seismic results. Our new study also accounts for the anomalous presence of 14 km-thick oceanic crust beneath the ARTC and its characteristic difference in petrology with other established subduction zones in the world.  相似文献   

马里亚纳海沟“挑战者深渊”最深点水深探测   总被引：1，自引：0，他引：1  

刘方兰  杨胜雄  邓希光  曲佳 《海洋测绘》2013,33(5):49-52

2011²012年,海洋六号船采用EM122多波束测深系统在马里亚纳海沟最深海域"挑战者深渊"进行的多波束水深测量,通过对测深资料进行分析处理,获得了高精度海底地形图,揭示了马里亚纳海沟挑战者深渊附近海底地形呈近东西向延伸,有西部、中部和东部三个洼地,它们由10800m等深线圈闭,长轴方向与海沟方向一致。洼地底部水深大于10900m,地形较为平坦。三个洼地最深区域分别由10916m、10904m和10915m等深线圈闭。三个洼地最大水深为10917m(误差小于20m),位于西部洼地内,中心位置为142°12.14'E,11°19.92'N。该处也是马里亚纳海沟最深点。  相似文献   

南海主要岛礁概率海啸风险评估          下载免费PDF全文

赵广生  牛小静 《海岸工程》2021,40(1):1-9

影响地震海啸的震源参数众多且具有很强的不确定性,充分评估海啸风险需要大量的情景模拟.本文基于建立的概率海啸风险模型,采用一种高效的海啸模拟方法,评估了南海主要岛礁的概率海啸风险.通过对历史地震数据的分析,综合考虑震级、震中位置、震源深度的随机性,形成了百万数量级的潜在地震情景集,并通过叠加近似方法实现了大量地震情景引发...  相似文献