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961.
962.
Living with disaster is an objective reality that human must face especially in China. A large number of earthquake case studies, such as the 2008 Wenchuan earthquake, 2010 Yushu earthquake, 2014 Ludian earthquake, have demonstrated that earthquake heavy damage and casualties stem from ground-faulting or rupturing along seismogenic active fault, near-fault high ground accelerations and building catastrophic structural failure. Accordingly, avoidance of active faults may be an important measure to effectively reduce earthquake hazard, which may encounter in the future, but how to avoid an active fault and how much a setback distance from the active fault is required to ensure that the ground faulting and rupturing has no any direct impact on buildings. This has been the focus of debate both for domestic and foreign scholars. This paper, first of all, introduces the definition of active fault. Then, quantitative analyses are done of the high localization of earthquake surface ruptures and relationship between the localized feature of the coseismic surface ruptures and building damages associated with the measured widths of the historical earthquake surface rupture zones, and an average sstatistic width is obtained to be 30m both for the earthquake surface rupture zones and heavy damage zones along the seismogenic fault. Besides, the widths of the surface rupture zones and spatial distribution of the building damages of the 1999 Chi-Chi earthquake and 2008 Wenchuan earthquake have also been analyzed to reveal a hanging-wall effect:Width of surface rupture zone or building damage zone on the hanging-wall is 2 or 3 times wider than that on its foot-wall for a dip-slip fault. Based on these latest knowledge learnt above, issues on avoidance object, minimum setback distance, location requirement of active fault for avoidance, and anti-faulting design for buildings in the surface rupture zone are further discussed. Finally, we call for national and local legislatures to accelerate the legislation for active fault survey and avoidance to normalize fault hazard zoning for general land-use planning and building construction. This preventive measure is significantly important to improve our capability of earthquake disaster reduction. 相似文献
963.
通过对内蒙古锡林浩特毛登牧场早石炭世花岗岩体进行野外观察、LA ICP MS锆石U Pb测年以及地球化学测试,讨论其构造环境,进一步为研究古亚洲洋闭合时限提供依据。测年结果表明:花岗闪长岩为(3306±18) Ma,二长花岗岩为(3277±26) Ma,成岩时代为早石炭世。岩石地球化学分析表明:花岗闪长岩为强过铝质、钙碱性系列岩石,具有活动大陆边缘的亲缘性特征。微量元素特征指示花岗闪长岩具有典型下地壳来源特征并伴有部分幔源岩浆混合作用,为弧岩浆岩。二长花岗岩为具高硅、富碱、相对低铝特征的高钾钙碱性系列岩石。两类差异明显的岩石稀土配分曲线表明二长花岗岩具有下地壳岩浆重熔的演化特征。微量元素特征指示样品为大陆弧环境下壳源重熔的成熟弧花岗岩。构造判别图显示花岗闪长岩为代表活动大陆边缘环境的I型花岗岩,而二长花岗岩则为指示活动大陆边缘弧后伸展环境的A2型花岗岩,二者构成I-A型复合岩体,说明研究区在早石炭世仍存在古亚洲洋向西伯利亚板块的俯冲作用,推测古亚洲洋此时尚未闭合。 相似文献
964.
We carried out a statistical test on the peak position of the big blue bump (BBB) of medium/small redshift AGNs of different luminosities. The main method is to compare the spectral index in the soft X-ray, SX and the power law index for the straight line joining 1050 Å in UV and 0.5 keV of soft X-ray, UV-SX. The distributions of these two quantities proved to be similar from their mean values and by the K-S test. Hence, between 1050 Å and 0.5 keV, a power law possibly holds. The statistics predict that the BBB peaks around 1050 Å. This statistical result can also be obtained in the soft X-ray-selected, low luminosity AGN sample, WF 93. This shows that, even though a soft X-ray excess generally exists in WF 93, the BBB may still peak around 1050 Å. However, there is no correlation between SX and UV-SX, indicating that there is still an unknown factor operating in the far and extreme ultraviolet (FUV and EUV), which while ensuring overall similarity in distribution, inhibits one-to-one correspondence between individual values. 相似文献
965.
V. Karas B. Czerny A. Abrassart M. A. Abramowicz 《Monthly notices of the Royal Astronomical Society》2000,318(2):547-560
The origin and the profile of the iron K α line from active galactic nuclei are studied. The model with a quasi-spherical distribution of clouds around a compact galactic nucleus is explored, in which the intrinsic spectral feature around 6–7 keV is substantially affected by Comptonization of primary X-rays. The predicted spectral profiles are influenced mainly by the motion of the clouds in the strong gravitational field of the centre, and by the orientation of the source with respect to the observer. The case of the Seyfert galaxy MCG–6-30-15 is examined in more detail and free parameters of the model are determined. A robust result is obtained: acceptable fits to the observed profile correspond to a spherical distribution of the clouds with strong self-obscuration effects and with a rather high value of ionization parameter. This is a different situation from that considered in the model of a cold illuminated disc. Nevertheless, geometrically flat (disc-type) configurations are not rejected. 相似文献
966.
967.
为了探讨芙蓉洞现代沉积物沉积速率和微量元素 (Mg,Sr) 的变化特征、控制机制以及气候环境指示意义,于2010年11月到2013年11月对芙蓉洞5个滴水点进行连续现场监测,并采集现代沉积物样品进行沉积速率计算和微量元素测定。结果显示:(1) 芙蓉洞5个滴水点的现代沉积物沉积速率与滴量、pH、Ca2+浓度以及PCO2等指标的关系表现出多样性。 其中MP4和MP5的沉积速率均与滴量呈正相关 (r=0.75, n=11, p<0.01; r=0.63, n=11, p<0.05),两个滴水点的沉积速率整体表现出雨季高、旱季低的变化规律,表明MP4和 MP5的沉积作用主要发生在雨季,其沉积速率的变化可以对季节性干湿度变化做出响应。(2) 2012-2013年年降水量明显增加,在稀释作用、水岩作用以及植物对元素差异性吸收作用的影响下,各滴水点现代沉积物整体呈现出Mg浓度减小而Sr浓度增大的趋势,Mg/Ca和Sr/Ca比值呈反相关关系,它们响应了年际尺度上降水量增加的气候信息。 相似文献
968.
通过航卫片解译和野外实地调查,对六盘山断裂带新活动特征开展详细研究。调查发现六盘山东麓断裂为一条全新世活动的逆左旋走滑断裂,而六盘山西麓断裂为晚更新世活动的挤压逆冲断裂,二者的构造活动控制和影响了本区的地貌发育和地震活动。同时利用SRTM数据提取六盘山东西两侧泾河和水洛河上游流域盆地水系,得到流域盆地面积-高程积分值(HI值)分布图,探讨本区活动构造和地貌的响应关系。分析结果表明,在相同的岩性条件下六盘山东侧的HI值要低于西侧,反映了活动断裂对本地区地貌演化特征的不同影响。上述地貌分析研究为认识和理解六盘山地区地貌演化以及控制因素提供了基础数据和思路。 相似文献
969.
970.