Use of Neural network to predict the peak ground accelerations and pseudo spectral accelerations for Mexican Inslab and Interplate Earthquakes

The use of Artificial Neural Networks (ANN) is explored to predict peak ground accelerations (PGA) and pseudospectral acceleration (SA) for Mexican inslab and interplate earthquakes. A total of 277 and 418 seismic records with two horizontal components for inslab and interplate earthquakes, respectively, are used to train the ANN models by using an ANN with a feed-forward architecture with a back-propagation learning algorithm. Both ANN with single and two hidden layers are considered. For comparison purposes, the PGA and SA values predicted by the trained ANN models are compared with those estimated with attenuation relations or ground motion prediction equations (GMPEs). The comparison indicates that the predicted PGA and SA values by the trained ANN models, in general, follow the trends predicted by the GMPEs. However, an extensive verification of the trained models must be conducted before they can be used for seismic hazard and risk analysis since, on occasion, the PGA and SA values predicted by the trained ANN models depart from the behaviour observed from the actual records.     

Paleomagnetism of mid-Cretaceous red beds in west-central Kyushu Island, southwest Japan: paleoposition of Cretaceous sedimentary basins along the eastern margin of Asia

A paleomagnetic study was carried out on the mid-Cretaceous sedimentary strata in west-central Kyushu Island, southwest Japan, to elucidate the origin of sedimentary basins along the Asian continental margin in the Cretaceous. We collected paleomagnetic samples from a total of 34 sites of the mid-Cretaceous Goshonoura Group, shallow-marine clastic deposits in west-central Kyushu, and characteristic remanent magnetizations were recognized from 18 horizons of red beds. Thermal demagnetization has revealed that the red beds contain three magnetization components, with low (<240°C), intermediate (240-480°C), and high (480-680°C) unblocking temperatures. The low unblocking temperature component is present-field viscous magnetization, and the intermediate one is interpreted as chemical remanent magnetization carried by maghemite that was presumably formed by post-folding, partial oxidation of detrital magnetite. Rock magnetic and petrographic studies suggest that the high unblocking temperature component resides largely in hematite (martite and pigmentary hematite) and partly in maghemite. Because of the positive fold test, this high temperature component can be regarded as primary, detrital remanent magnetization. The tilt-corrected mean direction of the high temperature component is Dec=65°, Inc=63° with α₉₅=5°, which yields a paleomagnetic pole at 39°N, 186°E and A₉₅=8°. A combination of this pole with those of the Late Cretaceous rocks in southwest Japan defines an apparent polar wander path (APWP), which is featured by a cusp between the Late Cretaceous and the Paleogene. A comparison of this APWP with the coeval paleomagnetic pole from northeast Asia suggests an approximately 50° post-Cretaceous clockwise rotation and 18±8° southward drift with respect to northeast Asia. The southward transport of the Cretaceous basin suggests that the proto-Japanese arc originated north of its present position. We propose that the coast-parallel translation of this landmass was caused by dextral motion of strike-slip faults, which previous geodynamic models interpreted to be sinistral through the Mesozoic. The change in strike-slip motion may have resulted from Mesozoic collision and penetration of exotic terranes, such as the Okhotsk microcontinent, with the northeastern part of Asia.     

红亚矮星研究进展

红亚矮星是甚小质量恒星中的贫金属成员,质量从约0.5M⊙ (M⊙为太阳质量)到H燃烧的最小质量(0.075M⊙～0.085M⊙,取决于金属丰度),其寿命长于哈勃年龄,是银河系结构和化学增丰史的重要示踪体.与银盘上数量最多的恒星成员红矮星不同,红亚矮星在太阳附近非常稀少,并且其运动学特征与盘矮星有较大差异,属于年老银河系...     

红壤旱地玉米、大豆间作生态系统的农田减灾效应

在红壤旱地进行了玉米、大豆间作生态系统的田间试验,并对试验结果进行了分析。分析结果表明,相对于单作生态系统而言,间作生态系统具有明显的减灾效应,具体表现在3个方面:一是提高土壤含水量,降低系统白天的温度,减缓温差,从而增强系统的抗旱能力;二是减轻病虫害,并且能增加天敌数量;三是抑制农田杂草的发生、发展,减轻杂草危害。研究结果认为,在红壤旱地推广该间作种植模式,可减轻灾害,减少农药使用量,保护红壤旱地生态环境,促进农业的可持续发展。     

中国南方红土年代地层学与地层划分问题

南方红土是我国热带、亚热带以各类岩石和第四纪松散沉积物为母质发育的红色风化壳,也是我国分布最广的第四纪土状堆积。本文在探讨第四纪松散沉积物上红色风化壳的形成机制的基础上,根据风化壳发育程度将其划分为砖红土风化壳、红壤土风化壳和红化土风化壳3种类型。南方地区第四纪松散沉积物主要有河流相沉积、滨海相海滩砂和海岸风成砂——"老红砂"以及以下蜀土为主的风尘堆积。近年来在上述沉积物中多处发现旧石器遗址,促进了南方红土的地层年代学研究。根据前人及近期对南方红土的研究成果,讨论了南方红土的年代地层学问题,提出了以风化壳岩性特征为基础的岩石地层单位初步划分框架:老红砂划分为中更新统北海组、晚更新统晋江组;风尘堆积划分为中更新统宣城组、晚更新统下蜀组;河流相沉积只划出中更新统白沙井组,晚更新统留待以后研究再划出。     

红层软岩遇水作用的孔隙结构多重分形特征

红层软岩内部孔隙具有随机、多样化的分布特点,孔隙结构的变化是影响其宏观力学性能的关键所在。由SEM扫描电镜获取岩样不同饱水时间下的细观结构图像,根据盒维数法计算出孔隙的分形维数,发现随着饱水时间的加长,孔隙的分形维数呈现增大趋势。同时对孔隙的数量、大小进行统计分析,得出不同饱水时间下岩样内部孔隙的分布特征。基于多重分形理论,采用统计矩的方法对孔隙结构进行定量表征。结果表明,孔隙结构的分配函数与q阶次趋于线性关系,验证了该结构的自相似性与无标度性,由广义分形维数D(0)>D(1)>D(2)说明了孔隙具有多重分形特征,由多重分形谱参数分析了孔隙结构的不规则性与复杂程度,更好地表征孔隙大小各异的分布情况。结合孔隙结构的多重分形特征与岩样抗压强度,建立起孔隙结构变化与其力学性能的关联性,对研究红层软岩的损伤过程具有一定的指导意义。     

红色旅游高质量发展评价指标体系与培育路径研究——以红色旅游城市为例

基于五大发展理念构建了红色旅游高质量发展评价体系,选取12个重点红色旅游城市为研究案例,探究了其红色旅游高质量演化特征,并运用多案例的定性比较法和典型案例的网络文本分析提出了高质量发展的培育路径。结果表明：（1） 案例地红色旅游高质量发展水平整体不高,地区差异显著,六大子系统中增长动力、增长结构和增长方式上升水平尤为显著。（2） 案例地红色旅游高质量发展存在极差化特征。具体引致各发展类型失配的障碍系统存在差异,且其主导障碍因素呈现由内部资源优势向外部环境协调转化的过程。（3） 多案例地驱动机制分析可知,红色旅游高质量发展是六大子系统共同作用的结果,其中增长动力是核心因子,增长结构是共生因子,增长方式是非敏感因子,增长形态是敏感因子,增长成果是外部性因子,增长基础是支撑因子。（4） 典型个案的内容分析提炼出了全方位扩大红色旅游的正外部性效应、优化数字经济格局下的红色旅游共生环境、激发红色研学的大众旅游市场需求共三大关键培育路径。     

Origin of the red earth and gravel deposits in Nankou piedmont,northwestern Beijing,China

Analytic results of the mechanical and chemical composition, clay minerals, sedimentary structures and microtextures of the red earth and gravel deposits in Nankou piedmont, northwestern Beijing, China, suggest that the deposits have nothing to do with glaciation but are palaeodebris‐flow deposits. During the period of their deposition, the climate was humid and hot with plentiful rainfall, and oxidation, physical and chemical weathering were rather intense. Copyright © 2000 John Wiley & Sons, Ltd.     

陆相红色盆地1∶5万填图的一种新方法———构造—岩性—岩相填图法

通过吉安—泰和盆地１∶５万区域地质调查实践，提出了构造—岩性—岩相填图法：首先在区域性资料分析的基础上，通过踏勘确立构造不整合面、相变换面，初步划分岩石地层单位的群、组；第二，测制剖面，详细研究构造不整合面、相变换面、同相叠复面等界面特征及被这些界面围限的岩石地层内部结构等，正式划分岩石地层群、组、段，建立岩石地层层序；第三，利用主干地质路线调查，建立盆地地层格架；第四，开展面上地质调查，完成１∶５万地质填图；最后，进行综合分析，选择重点区段、剖面进行详细研究，总结盆地沉积模式