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11.
SeismicmomenttensorrepresentationsandradiationpaternsinunboundedmediawithelipsoidalcavitiesdrivenbylowfrequencypressurePI... 相似文献
12.
豫西南蒲塘金矿床地质特征及成因探讨 总被引:4,自引:0,他引:4
蒲塘金矿床属爆破角砾岩型,主成矿期温度236~318℃,主矿体受爆破角砾岩筒控制,含矿围岩蚀变及矿体变化规律明显,黄铁矿及黄铜矿是金的主要载体矿物。矿石中Au-Cu含量呈正消长关系,成矿物质主要来源于花岗岩,从花岗岩的侵入到矿床的形成,大体上经过了晚燕山期浅成初始岩浆侵入-爆破,超浅成强烈爆破及热液成矿三个阶段。 相似文献
13.
J. Martí A. Geyer J. AndujarF. Teixidó F. Costa 《Journal of Volcanology and Geothermal Research》2008
Since the onset of their eruptive activity within the Cañadas caldera, about 180 ka ago, Teide–Pico Viejo stratovolcanoes have mainly produced lava flow eruptions of basaltic to phonoltic magmas. The products from these eruptions partially fill the caldera, and the adjacent Icod and La Orotava valleys, to the north. Although less frequent, explosive eruptions have also occurred at these composite volcanoes. In order to assess the possible evolution Teide–Pico Viejo stratovolcanoes and their potential for future explosive activity, we have analysed their recent volcanic history, assuming that similar episodes have the highest probability of occurrence in the near future. Explosive activity during the last 35000 years has been associated with the eruption of both, mafic (basalts, tephro–phonolites) and felsic (phono–tephrites and phonolites) magmas and has included strombolian, violent strombolian and sub-plinian magmatic eruptions, as well as phreatomagmatic eruptions of mafic magmas. Explosive eruptions have occurred both from central and flank vents, ranging in size from 0.001 to 0.1 km3 for the mafic eruptions and from 0.01 to < 1 km3 for the phonolitic ones. Comparison of the Teide–Pico Viejo stratovolcanoes with the previous cycles of activity from the central complex reveals that all them follow a similar pattern in the petrological evolution but that there is a significant difference in the eruptive behaviour of these different periods of central volcanism on Tenerife. Pre-Teide central activity is mostly characterised by large-volume (1–> 20 km3, DRE) eruptions of phonolitic magmas while Teide–Pico Viejo is dominated by effusive eruptions. These differences can be explained in terms of the different degree of evolution of Teide–Pico Viejo compared to the preceding cycles and, consequently, in the different pre-eruptive conditions of the corresponding phonolitic magmas. A clear interaction between the basaltic and phonolitic systems is observed from the products of phonolitic eruptions, indicating that basaltic magmatism is the driving force of the phonolitic eruptive activity. The magmatic evolution of Teide–Pico Viejo stratovolcanoes will continue in the future with a probably tendency to produce a major volume of phonolitic magmas, with an increasing explosive potential. Therefore, the explosive potential of Teide–Pico Viejo cannot be neglected and should be considered in hazard assessment on Tenerife. 相似文献
14.
Lionel Wilson 《Geophysical Journal International》1999,136(3):609-619
Previous treatments of the relationship between the mass fraction of released magma volatiles and the eruption speeds of gas and pyroclasts in steady explosive eruptions have not taken detailed account of the dynamic effects associated with the finite size distribution of the pyroclasts. When this is done, it is found that previously published estimates of exsolved magma volatile contents obtained from the analysis of pyroclast size distributions in near-vent deposits overestimate the volatile content by approximately 20 per cent in the case of Plinian eruptions. The discrepancy is much worse for pyroclast size distributions skewed towards coarse clasts, as is common in basaltic lava fountains; in such cases pyroclast dispersal studies may overestimate the exsolved magma volatile content by at least 200 per cent. An analogous problem arises if released magma volatile amounts deduced from studies of fluid inclusions in pyroclasts are inserted into most current computer models of eruption dynamics, but the gas eruption speeds deduced have an even larger error, being underestimated by up to 300 per cent in the case of coarse-grained eruptions. The more sophisticated of the currently available numerical models of eruption dynamics can in principle avoid this problem, but practical implementation limitations have so far prevented such models being run with a sufficiently wide range of grain sizes for the importance of these effects to be fully appreciated. 相似文献
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利用加拿大大气环境局第二次冬季风暴观测(简称CASPⅡ)的部分资料,对加拿在东海岸冬季风暴的发生,发展情况进行了分析,结果表明,大多数风暴能达到爆发性发展程度,并对其中一个形成眼区的强风暴例子做了进一步讨论。 相似文献
17.
罗继辉 《水文地质工程地质》1999,26(2):57-59
本文工程设计阐述了在动水条件下,封堵水平巷道的“三段式”组合灌浆方法,以及定向钻进在地下深井巷堵水工程中的应用。 相似文献
18.
使用FNL Analysis全球格点资料,对东北太平洋一次强爆发性气旋的特殊性进行了分析,发现气旋对其西北部低压系统的吸收合并是其爆发性发展过程中的典型特征,斜压强迫对其快速发展的作用较弱,与西北太平洋爆发性气旋的发展过程存在显著差异。同时,使用Zwack-Okossi诊断方程,从影响爆发性发展的动力和热力因子方面,对其发展机制作了深入的探讨。研究表明,正涡度平流、暖平流和非绝热加热的共同作用使气旋开始爆发性发展,由潜热释放导致的非绝热加热的贡献最大,非绝热加热是其快速发展的主导因子,其中正涡度平流贡献主要来自于中高层,暖平流的贡献主要来自于中低层和高层,而非绝热加热主要发生在中低层,这为东北太平洋爆发性气旋的发展机制提供了一个新的认识。 相似文献
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20.
利用高时空分辨率的欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)对全球气候的第五代大气再分析数据集(European Re-Analyses 5, ERA5),对比分析了2020年7月淮河上游地区的两次江淮气旋过程,并结合海洋—大气—波浪—泥沙耦合模式(Coupled Ocean-Atmosphere-Wave-Sediment Transport modeling system, COAWST)进行敏感性试验,探讨同一气候尺度背景下,高低频大气环流形势和海气耦合作用对江淮气旋的影响。结果表明,低空环流形势的高频变化和海表温度的升高对气旋的大风影响和强度发展有重要作用。低空环流形势中,存在“气旋—反气旋—气旋”环流天气尺度波列,易造成气旋大风叠加增强;海气交互界面的高海表温度加热作用导致的感热和潜热释放通过气旋北部弯曲锋面强烈的上升运动,为气旋发展提供能量,促进气旋入海后爆发性增强。 相似文献