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111.
In this research, experimental applications have been performed to reduce blast induced vibrations in open pit mines. For
this purpose, artificial discontinuity zones such as barrier holes and trench were opened in a dragline panel of Seyitomer
Lignite Enterprise, Kutahya, Turkey. Peak particle velocities in front of and behind them were measured by seismographs. In
this way, their effect against vibration was observed and compared. Barrier holes were opened 24 m deep through 3 parallel
lines and aligned at 1 m spacing. On the other hand, the trench had 8 m depth and 4 m width. During the research, 209 measurements
were taken belonging to 105 explosions. Twenty-eight explosions were carried out in the barrier holes experiments and 77 explosions
were carried out in the trench experiments. A decrease in vibration of 14.3–18.5% was obtained behind the barrier holes while
a decrease of 24.8–58.1% was provided by the trench. 相似文献
112.
Abstract The Japan Trench forearc offshore Honshu Island in northeast Japan, where the 130‐m.y.‐old Pacific oceanic plate is presently subducted, was drilled during the Ocean Drilling Program Leg 186. Results from mechanical and sedimentological studies of claystones recovered from Sites 1150 and 1151 in the overlying erosional forearc wedge are reported in the present study. Although many physical properties are similar in the seismic (Site 1150) and aseismic portion (Site 1151) of the shallow forearc, Site 1150 displayed a higher abundance of open fractures, two prominent fault zones and enigmatic pore fluid signatures in the claystones. The abundance of weak mineral phases, together with high smectite contents (from X‐ray diffraction), control the low friction coefficients of 0.33–0.39 of the claystones in ring‐shear experiments. Results from triaxial testing proposed overall low magnitudes of in situ effective vertical stress, with somewhat lower values at Site 1150 than at Site 1151. Similarly, samples from Site 1150 displayed slightly higher pore fluid pressures than those at Site 1151. The high sediment porosities, which are in part also a result of intact diatom tests (from scanning electron microscope), together with the anomalous fluid signatures and elevated pore fluid pressures, could very likely result from upward migration and influx of deep‐seated waters. Dewatering reactions at depth result in enhanced pore fluid pressure transients along out‐of‐sequence thrusts and consequently lower effective stress. At depths greater than that of Leg 186 drilling, elevated pressure–temperature conditions trigger mineral transformation and cementation, which result in increasing friction, unstable sliding and seismic rupture. Such earthquakes could have repeatedly disaggregated the consolidated claystone fabrics at the seismic site, and could be responsible for differences in yield strength and cementation when compared to the aseismic Site 1151. 相似文献
113.
Nobuaki Niitsuma 《Island Arc》2004,13(1):306-317
Abstract Seven chronostratigraphic stages were established based on the correlation of magneto‐biostratigraphic marker horizons within the Deep Sea Drilling Project and Ocean Drilling Program cores from the forearc of the Japan Trench. Because the stages are coeval with changes in the rate of sedimentation, lithofacies, magnetic intensity and composition of fossil assemblages, they probably reflect the tectonic situation in the Japan Trench forearc and also in the arc–trench system. The stages correlate to the tectonic events of the Japanese Island Arcs; for example, evolution of the Boso triple junction, initiation of Philippine Sea Plate subduction and the Japan Sea opening. 相似文献
114.
本文采用依赖温度的黏度结构以及考虑海洋板块和大陆板块厚度差异等特征,以太平洋板块向欧亚板块会聚速率作为板块速度的主要约束,通过变化海沟后撤速度模型,数值模拟西太平洋板块向中国东北的俯冲过程.结果表明,要产生类似于中国东北之下低角度的板片俯冲,海沟后撤是重要条件;而上下地幔黏度的较大差异是决定俯冲板片不穿透660 km相变面的决定因素;西太平洋板块向欧亚板块的俯冲应早于70 Ma B.P.,海沟后撤速度可能小于一些地质学家估计的45 mm/a, 而且可能是分阶段变化的;速度场表明运动学模型的反过程:大陆岩石圈之下物质的不断水平向东的流动和推挤可能成为海沟后撤的力源之一,地幔物质的这种东向流动可能与印度板块挤压碰撞欧亚板块有关,沿欧亚板块东缘的扩张构造可能是太平洋-欧亚板块运动和印度-欧亚板块运动的综合效应. 相似文献
115.
Sediment collapse and subsequent lateral downslope migration play important roles in shaping the habitats and regulating sedimentary organic carbon(SOC) cycling in hadal trenches.In this study,three sediment cores were collected using a human-occupied vehicle across the axis of the southern Yap Trench(SYT).The total organic carbon(TOC) and total nitrogen(TN) contents,δ13C,radiocarbon ages,specific surface areas,and grain size compositions of sediments from three cores were measured.We... 相似文献
116.
菲律宾群岛受到欧亚板块、菲律宾海板块和印度-澳大利亚板块的碰撞作用,地质环境复杂,构造因素多样.尽管近几年来已经有了少数关于该区域层析成像的研究,但这些研究的区域主要集中在马尼拉海沟、吕宋岛及中菲律宾地区,而关于群岛周围其他海沟和南菲律宾地区的讨论相对较少.到目前为止,还没有同时获得过关于菲律宾群岛深部纵、横波速度结构的研究,本次研究通过反演155779条P波震相和59642条S波震相,同时获得了菲律宾群岛从地表至150 km深度的纵、横波速度结构.地震层析成像结果表明该地区的壳幔速度结构具有较强的不均一性,地壳内部存在着广泛的低速异常,而表征俯冲板块的高速异常则沿着群岛周边的海沟展布.南海块体在马尼拉海沟中段的俯冲角度和俯冲活动性比南段小;菲律宾海板块在东吕宋海槽南段微弱的俯冲作用很有可能同本哈姆海台的碰撞有关.菲律宾群岛大部分MW>6.0的强震沿着各个板块的边界发生,体现出菲律宾海板块同欧亚板块之间的强耦合作用,群岛西侧的南海块体在马尼拉海沟16°N-20°N之间呈现出的弱耦合状态可能跟北吕宋地区的拉张应力环境有关,南海块体在16°N以南的地区同上覆块体之间的耦合作用较强;群岛东侧的菲律宾海板块在14°N以北的地区没有强震发生,它与菲律宾群岛之间的耦合程度从北向南逐渐增强,在12°N以南的地区要强于12°N以北的地区;此外苏禄海盆和菲律宾构造带之间也存在着强耦合关系. 相似文献
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