Fractal-statistical analysis of grain-size distributions of debris-flow deposits and its geological implications     

Huayong Ni  Wanmo Zheng  Xilin Liu  Yanchao Gao 《Landslides》2011,8(2):253-259

Breakage models and particle analyses have been widely used as tools for describing and interpreting various deposits and providing parameters for assessing the particle-size distribution of the deposits. Debris flows can be seen as a two-phase rheological fluid with a clay-fluid composition, and debris-flow deposits comprise mud, silt, sand, and boulders, with grain sizes ranging from less than one μm to more than several meters. As a consequence, according to fractal theory, the particles in debris-flow deposits have self-similarity in geometrical shape and scale invariance in size. In this paper, the fractal dimensions of particles in various debris-flow deposits are calculated and corresponding fractal features are determined based on fractal-statistical theory. The aims of the study are: to provide a quantitative grain parameter that reflects both the grain composition and grain-size distribution in debris-flow deposits; to compare the fractal dimensions of grains in different types of debris-flow deposits and the degree of self-organization of debris flows; as well as to discuss the geological implications of fractal dimensions and fractal features of particles in debris-flow deposits.  相似文献   

煤田采区高分辨三维地震勘探激发参数的优选     

蔺国华  倪新辉  杨文强 《中国煤炭地质》2011,(10):62-65

三维地震勘探取得可靠数据的前提是获得最佳的的激发参数,即激发井深和激发药量。双井微测井是一种行之有效的确定激发参数的方法。以某区25m双井微测井为例,介绍了通过不同激发井深的接收排列图及频谱分析图确定潜水面位置及最佳激发深度的方法;在确定的最佳激发层位上进行不同药量试验,结合目的层有效波时窗频谱图,综合考虑有效信号、地震子波频谱及信噪比等因素选择最佳激发药量。通过双井微测井工作,最终确定潜水面位置为6m,最佳激发深度为11m,激发药量为2kg。  相似文献   

Geomorphological and sedimentological comparison of fluvial terraces and karst caves in Zhangjiajie,northwest Hunan,China: an archive of sandstone landform development     

Guifang Yang  Xujiao Zhang  Mingzhong Tian  Yamin Ping  Anze Chen  Zhiliang Ge  Zhiyun Ni  Zhen Yang 《Environmental Earth Sciences》2011,64(3):671-683

The Zhangjiajie Sandstone Peak Forest Geopark (Zhangjiajie World Geopark) of northwest Hunan, China hosts a well-preserved sequence of fluvial terraces and karst caves. In this contribution, a comparative study of fluvial terraces with karst caves along the middle-lower Suoxi River in Zhangjiajie World Geopark is presented to improve the understanding of the development of striking sandstone landscape in the upper Suoxi River. By integrating geomorphological, sedimentological, and geochronological techniques, the possible correlation between fluvial terraces and karst caves, as well as their climatic and tectonic implications is investigated. The available electron spin resonance and thermo-luminescence numerical ages coupled with morphostratigraphic analysis indicate that aggradation of fluvial terrace levels occurred at ca. 347 ± 34 ka (T₄), 104.45 ± 8.88 to 117.62 ± 9.99 ka (T₃), 60.95 ± 5.18 ka (T₂), and Holocene (T₁), followed by the stream incision. Fluvial terrace levels (T₄ to T₁) correlate morphologically with the karst cave levels (L₁ to L₄), yet the proposed chronology for the fluvial terrace levels is a bit later than the chronological data obtained from karst caves. In northwest Hunan, where a unique sandstone peak forest landscape was extensively developed, the fluvial terrace sequences as well as the cave systems are the important archives for studying the evolution of the sandstone landscape. The beginning of the sandstone landscape development must be earlier than the aggradation of the fluvial terrace T₄, allowing this unique landscape to occur in the Middle Pleistocene.  相似文献   

赣州农业巨灾保险气象灾害指数设计          下载免费PDF全文

谢远玉  谢妍玥  张韵启  高晶  谢亦飞  黄志远 《气象与减灾研究》2021,44(3):209-214

农业巨灾保险可有效分散灾害的风险,气象灾害是造成农业巨灾的主要灾害之一,因此设计合理的气象灾害保险指数可为农业巨灾保险提供科学的技术支撑.利用赣州市17个县(市、区)国家气象站1981—2020年和区域气象站2011—2020年观测资料,结合赣州气候以及气象灾害出现特点,经专家咨询和调研,确定暴雨、冰霜冻害、干旱和大风等4种气象灾害作为赣州农业巨灾保险的气象灾种.根据不同灾害出现的气候概率以及投保单位的要求,设计了赣州农业巨灾保险不同等级的气象灾害指数,并确定农业巨灾保险气象灾害赔付的触发概率范围为45％—70％.经验证,赣州农业巨灾保险气象灾害指数可用.  相似文献   

四川盆地中三叠统雷口坡组有利沉积相带及岩相古地理特征   总被引：2，自引：0，他引：2  

吕玉珍  倪超  张建勇  谷明峰  孙秋分  刘志上  辛勇光 《海相油气地质》2013,(1):26-32

依据四川盆地古地理背景和古气候条件,结合中三叠统雷口坡组野外剖面、岩心和薄片的观察以及单井和连井沉积相等的分析认为,盆地周边水下隆起的障壁作用和干旱炎热气候条件共同影响雷口坡组的沉积相特征,海平面升降变化是控制沉积相发育和空间分布的重要因素。雷口坡组总体为一套障壁蒸发潟湖沉积,可分潟湖边缘坪、潟湖、潮坪和台缘障壁四种沉积亚相类型,并可进一步划分出多种微相。台缘障壁亚相潟湖边缘白云岩坪和颗粒浅滩是有利的沉积相带。雷口坡组可划分出SQ1—SQ4四个层序。绘制了雷口坡期各时段体系域的岩相古地理图,并分析了它们的岩相古地理特征。  相似文献   

ENSO对亚洲夏季风异常和我国夏季降水的影响   总被引：21，自引：11，他引：21  

邹力  倪允琪 《热带气象学报》1997,13(4):306-314

首先对ＥＮＳＯ过程中亚洲夏季风环流的变化进行了诊断分析，结果表明在Ｅｌ Ｎｉｎｏ事件和ＬａＮｉｎａ事件中亚洲夏季风系统各成员均发生不同程度的变化，甚至出现相反的变异特征。其中，对我国东部地区夏季降水进行了ＥＯＦ分析，并在此基础上分析了赤道太平洋ＳＳ－ＴＡ对我国东部地区夏季降水影响的区域和程度，该影响与ＥＮＳＯ循环的发展阶段密切相关，且在长江中下游地区和华南地区最为显著。  相似文献   

气候变化对阿拉善荒漠植被的影响研究   总被引：15，自引：10，他引：5  

张凯  司建华  王润元  王小平  韩海涛  郭铌 《中国沙漠》2008,28(5):879-885

利用1982—2003年NASA GIMMS归一化植被指数(NDVI)数据集和阿拉善左旗、右旗和额济纳旗气温和降水资料,对阿拉善地区NDVI变化和气候变化特征及其相互关系进行了分析。结果表明：①1982—2003年东部地区(左旗植被指数略有增加,而中部(右旗)和西部地区(额济纳旗)则呈下降趋势。季节变化东、中、西部表现不同。左旗和额济纳旗多年平均NDVI的月变化和右旗相反。②东部地区升温率最大,其次是西部和中部地区。降水表现为东部和西部地区(额济纳旗)稍有增加,而中部地区(右旗)呈缓慢减少趋势。季节变化东、中、西部表现不同。多年平均气温和降水量的月变化趋势东、中、西部一致,呈单峰型曲线。③东部地区和中部地区,降水量与植被指数存在明显的年相关、隔季和当季相关,而西部地区额济纳旗没有明显的相关性。阿拉善地区NDVI同温度的相关性不好。  相似文献   

Tracing sewage pollution in the Pearl River Delta and its adjacent coastal area of South China Sea using linear alkylbenzenes (LABs)   总被引：4，自引：1，他引：3  

Luo XJ  Chen SJ  Ni HG  Yu M  Mai BX 《Marine pollution bulletin》2008,56(1):158-162

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Heating Stage Experimental Study of Melt Inclusions in Feldspars from Three Holocene Eruptions of Changbaishan Tianchi Volcano     

Li Ni  Nicole Métrich  Fan Qicheng 《中国地震研究》2008,22(2):153-163

There occurred several eruptions from Changbaishan Tianchi volcano in Holocene, and at least three of them were believed to be true according to the formal studies. The products of three eruptions were yellow comenditic pumice of - 5000a B.P. （Eruption Ⅰ ）, gray comenditic pumice and pyroclastic flow of - 1000a B.P. （ Eruption II, i.e. the millennium explosive eruption）, black trachy pumice and welded tuff of - 300a B.P. （ Eruption Ⅲ ） respectively. There were a large number of melt inclusions found in phenocrysts, which differ in size and color. The Leitz 1350 heating stage experiments for melt inclusions in host feldspars from three Holocene eruptions of Changbaishan Tianchi volcano imply that there were little differences between the homogenization temperatures of melt inclusions from Eruptions Ⅰ and Ⅲ, whereas it was rather complicated for Eruption H, i.e. there might be two kinds of melt with different homogenization temperature periods, which gave the evidence for the assumption that the explosive millennium eruption of Tianchi volcano was triggered by injection and mixing of two different magmas. The experimental results also indicate that （ 1 ） small melt inclusion is easy to be homogenized, while the large one, especially the one with lots of daughter crystals, is rather difficult to be homogenized; （2） homogenization temperature closely correlates with the size of melt inclusion within host crystal, with the temperature point switching from high heating rate to low heating rate, and correlates with whether it is the first time to obtain homogenization as well; and （3） a melt inclusion can get different homogenization temperatures when it is repeatedly heated. Even more, the next homogenization temperature is usually higher than the former one, which testifies the phenomenon that hydrogen migration occurs during repeated heating.  相似文献   

Lowermost mantle shear velocity anisotropy beneath Siberia     

杨凤琴  刘斌  倪四道  曾祥方  戴志阳  吕彦 《地震学报(英文版)》2008,21(2):213-216

Introduction D’’ layer plays an important role in geodynamic process. And seismological research indicates that D’’ layer has large scale seismic anisotropy, however, most research concentrated on areas such as Northern Pacific, Central Pacific, Caribbean, Central America, Alaska etc. (Wookey et al, 2005; Garnero and Lay, 2003; Matzel et al, 1996;  相似文献