Stratigraphic Implications of Skeletal Microfossils from the Cambrian of Korea: A Preliminary Report

Diverse small shelly fossils and other associated fossils were recently recovered from the Cambrian Hanaeri section, southwestern Mungyeong, Korea. The fauna includes conoidal problematica, poriferans (sponge spicules), coeloscleritophorans (chancelloriids), brachiopods, monoplacophorans, trilobite (?) fragments, echinoderms, and conodonts. A preliminary assessment of faunal associations, stratigraphic implications, and the correlation of these skeletal fossils is given, based on occurrences of Actinotheca cf. mira (He), Microcornus sp., Torellela laevigata (Linnarsson), Torellela sp., Archiasterella quadratina Lee, Chancelloria sp., Lingulella sp., Prototreta sp., Phakelodus tenuis (Müller), Phakelodus elongates (An), Hertzina sp., and Furnishina sp.     

2011年日本东北地区太平洋近海地震对亚洲板块及韩国大地控制网的影响分析

本研究分析了2011年3月11日发生的M_w9.0日本东北地区太平洋近海地震对亚洲地区和韩国国内GPS卫星常年跟踪站的位移影响.为此,利用了日本东北地区太平洋近海地震发生前后两周(2011年3月4日到3月18日)的GPS站点数据,包括震中附近地区(韩国,中国,中国台湾地区,日本和俄罗斯)55个GPS卫星常年跟踪站和284个IGS 全球跟踪站,并采用GAMIT/GLOBK软件进行处理和平差,估算出所有GPS站点的同震形变.结果显示,日本东北地区太平洋近海地震引起的同震形变影响在亚洲地区比较明显,包括日本和附近国家,距离震中2702 km的中国武汉(WUHN)站也观测到同震形变.为精确分析日本东北地区太平洋近海地震对韩国国家大地控制网的影响,通过GAMIT/GLOBK软件计算出韩国GPS卫星常年跟踪站之间的基线长度变形,并分析出弹性变形量.结果表明:大部分GPS站点均向震中方向膨胀,且向震中的垂直方向收缩.由日本东北地区太平洋近海地震导致的最大剪应变达到韩国国家大地控制网年均变形率的约7倍,对韩国的地壳产生14.5~57.7 mm的水平位移,并导致韩国国家大地控制网产生弹性变形.因此,在不及时更新维护韩国国家大地控制网的情况下,GPS测量成果将会发生最大20 mm的位置误差.     

土工织物加筋黏性土坡坡顶加载的离心模型试验研究

土工织物加筋技术在工程中得到了广泛的应用,取得了良好的加固效果。但对于土工织物加筋机制尚缺乏明确和统一地认识,加筋理论研究落后于工程实践。为此,进行了坡顶加载条件下土工织物加固黏性土坡和素土边坡的离心模型试验,记录和再现了素土边坡和加筋土坡在坡顶加载条件下的变形破坏过程。主要基于变形分析探讨了黏性土坡在土工织物简单加固条件下的加固效果和加筋机制。结果表明,土工织物加筋可以有效地提高黏性土坡的极限承载力,加筋带的存在改变了土体的位移场,扩大了坡顶加载的影响区域,加筋后滑裂面明显后移。加筋带对土体的局部作用和作用范围,随着土体变形的增大而增大和扩展     

Three-dimensional saltating processes of multiple sediment particles

The purpose of this study was to investigate the interacting mechanism between the saltating particles near a channel bed. A three-dimensional real-time flow visualization technique was developed to measure the interparticle collision behaviors during the saltating process. Based on the experimental data, the distribution of the collision points was found to be symmetric. This confirms the assumption that the projections of the collision points onto the reasonable plane are uniformly distributed. A three-dimensional saltating model was also developed. This model produced satisfactory results. The model is able to simulate the continuous saltating trajectories of several particles. The simulated dimensionless saltating height, longitudinal and vertical saltation velocity components were found to increase as the dimensionless particle diameter and the dimensionless flow transport capacity parameter increase, while the simulated lateral saltation velocity component varies inversely with the dimensionless flow transport capacity parameter. A regression equation for the bed load transport rate was also obtained.     

香港的新构造断裂活动与天然山体滑坡关系的初步研究

香港沙田河沥背地区西北向断裂的左旋错断构造运动,在断裂两分支之间造成转变挤压型地块抬升,形成一菱形地垒。表土层大致均匀分布在地垒及其两侧地区,并且没有被埘北向断裂错动。而表土层所覆盖的古台地亦没有经过明显剥蚀。待得到河沥背表土层及邻近黄竹洋村天然山体滑坡定年结果资料,即可以给出河沥背断裂最新错动年龄范围及断裂活动与区内天然山体滑坡事件的相互关系。     

澳门土壤剪切波速的相关性分析

土壤的剪切波速(VS),是抗震设计的一个重要参数,但有关澳门土层的相关资料则十分稀少。研究的主要目的是根据近期野外测试的结果,探讨澳门土层的VS与标准贯入试验的打击锤数(N)的关系,并以简单之幂函数建立VS与N值的关系式。作为澳门轻轨交通系统之勘察计划,研究进行了五组下孔法(DH),地震波圆锥触探试验(S-CPT)以及标准贯入试验(SPT)的测试。根据试验结果所得的关系式估算剪切波速高于较澳门轻轨设计大纲的建议值,而使用另一有关澳门土层的数据库来验证新的关系式,亦可获得合理的决定系数。     

Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials

Abstract— Primitive meteorites exhibit certain features that are consistent with aqueous and thermal alteration on asteroids, but O‐isotopic analyses show only a modest heavy‐isotope shift, interpreted as indicating modification in the nebula. To understand the isotopic effects of asteroidal alteration, we take the L‐group ordinary chondrites weathered in Antarctica as an analogue. The data show that alteration is a two‐stage process, with an initial phase producing only a negligible isotopic effect. Although surprising, a possible explanation is found when we consider the alteration of terrestrial silicates. Numerous studies report pervasive development of channels a few to a few tens of nanometer wide in the incipient alteration of silicates. We observe a similar texture. Alteration involves a restructuring of clay minerals along these narrow channels, in which access of water is restricted. The clay shows a topotactic relationship to the primary grain, which suggests either epitaxial growth of the clay using the silicate as a substrate or inheritance of the original O structure by the clay. Our data suggests the latter: with extensive inheritance of structural polymers by the weathering product, the bulk O‐isotopic composition is comparatively unaffected. This offers an explanation for the lack of an isotopic effect in the weathering of the L chondrites. If substantial modification of chondritic materials may occur without a pronounced isotopic effect, it also reconciles existing O analyses of CV chondrites with an asteroidal model of aqueous alteration.     

Australasian microtektites in the South China Sea and the West Philippine Sea: Implications for age,size, and location of the impact crater

Abstract— Microtektites from two deep‐sea cores in the South China Sea and the West Philippine Sea are identified as belonging to the Australasian tektite strewn field based on the morphology, chronostratigraphic occurrence, and geographical location of these microtektites. The higher concentrations of microtektites (>1000/cm²) in the marginal seas of the western Pacific, with the peak concentration in the South China Sea, support the hypothesis of a large impact crater in Indochina. These two new occurrences lead to a more precise dating of the impact event at 793 ka, whereas the size of the Australasian source crater on the Indochina Peninsula is estimated to be 90–116 km.     

Differentiations of geographic distribution and subsistence strategies between Tibetan and other major ethnic groups are determined by the physical environment in Hehuang Valley

The people of the Tibetan Plateau have received extensive attention from scholars because of their unique adaptability to the low temperature and anoxic environments. However, the Tibetan communities and their habitats in the low-altitude regions of the plateau have rarely been studied in a scientific manner. Based on the extraction of geographic information of 197 towns in the Hehuang Valley and on variance analysis, this study examines the habitats and subsistence strategies of the Tibetans and other major ethnic groups in the low-latitude region of the Tibetan Plateau. Our statistical results show that the annual average temperature of Tibetan habitats in the Hehuang Valley is relatively high. The relatively warm environment of the valley allows the Tibetans in that area to cultivate wheat and barley and raise cattle and sheep—a subsistence strategy significantly different from that of other Tibetans in the high-altitude regions in the Tibetan Plateau. In addition, the Tibetan communities in the Hehuang Valley include similar agri-pastoral ethnic groups (including Hui and Salar), both of which adopt similar subsistence strategies. The agricultural ethnic groups (Han and Tu) live in a relatively cool and humid environment facilitating agricultural production, while the agri-pastoral ethnic groups (Tibetan, Hui, and Salar) inhabit relatively warm and arid environment in the valley. Due to the lack of agricultural activities, agri-pastoral groups must also engage in animal husbandry to supplement their diet. In the Ando Tibetan region, the subsistence strategies of the ethnic groups are closely related to their physical environment.Those ethnic groups communicate among themselves, integrate, and influence each other, resulting in a diversified culture. This study proves that the habitat variation at a regional scale corresponds significantly to the variation of subsistence strategies. Our findings may further refine knowledge about the human-environmental relationships of Tibetans and lead future research towards using quantitative methods to analyse the intersection of physical environment and ethnic groups' distribution.     

From the editors

正Dear Members of the Editorial Board,Contributors and Friends,2018 is the tenth anniversary of the Wcnchuan earthquake disaster.To commemorate the Wenchuan earthquake disaster,the journal of Earthquake Engineering and Engineering Vibration(EEEV)will publish special sections with invited papers in the issues of 2018.We sincerely appreciate the contributions from the following experts:Professor Masayoshi NAKASHIMA.Professor Hongnan LI,and Professor Ying ZHOU.