Seismic hazard assessment for Guatemala City     

M. Villagran  C. Lindholm  A. Dahle  H. Cowan  H. Bungum 《Natural Hazards》1996,14(2-3):189-205

Guatemala is one of the Central American countries that for some years now have been participating in a regional program for natural hazard assessment and disaster reduction, funded by the Nordic countries and coordinated by a regional institution (CEPREDENAC). Recent work related to seismic hazard has included the standardization, reporting and processing of seismicity data across the borders, followed by regional hazard modeling. The work presented here for Guatemala City represents a step from a regional to a more local level, based on reevaluation of historical seismicity, geological data related to active faults, and attenuation relations recently derived from analysis of strong motion records from the region. The site specific hazard calculations indicate that expected values of peak ground acceleration are ranging from less than 2 to more than 6 m s^–2, corresponding to annual exceedence probabilities ranging from 0.1 to 0.001, respectively.

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“波西米亚地块”超大型多因复成铀矿床特征及其成矿大地构造背景     

刘翔 《大地构造与成矿学》1996,20(4):298-309

“波西米亚地块”是世界重要的铀资源产地之一，本文强调了该区超大型多因复成铀矿床的特征，分析了该区成矿的历史－动力学大地构造背景，认为该区超大型多因复成铀矿床的形成是因为具有富铀的前地槽残留稳定陆壳基底、长期活动的深断裂带、富铀的有利岩性建造和后期强烈的地洼型构造岩浆活化作用的结果。通过对比分析，指出中国华南地区存在相似的区域成矿地质条件，具有寻找超大型多因复成铀矿床的前景。  相似文献   

Central Taimyr accretionary belt (Arctic Asia): Meso–Neoproterozoic tectonic evolution and Rodinia breakup     

V. A. Vernikovsky  A. E. Vernikovskaya 《Precambrian Research》2001,110(1-4)

The structure and tectonic position of the Neoproterozoic Central Taimyr accretionary belt of northwestern Siberia is dominated by the Faddey and Mamont-Shrenk granite-gneiss terranes, ophiolites, and back-arc volcanic rocks. Granites in the granite-gneiss terranes are S-type and formed between 900 and 850 Ma from 1.9 to 1.8 Ga continental crust. U–Pb and Sm–Nd isotopic studies show that the plagiogranites of the Chelyuskin ophiolite belt formed between 850 and 740 Ma. The ophiolite complex was metamorphosed to garnet amphibolite grade around 600 Ma, which is considered to be when the accretionary belt was obducted onto the Siberian continent. Comparison of principal structures of the Central Taimyr accretionary belt with similar structures in Arctic countries permits definition of the principal stages of the Neoproterozoic destruction of the supercontinent Rodinia, in the Arctic region.  相似文献   

克鲁格曼的多中心城市空间自组织模型评析   总被引：19，自引：2，他引：19  

刘安国  杨开忠 《地理科学》2001,21(4):315-322

在传统的空间经济格局研究中，以杜能为代表的古曲区位论和以克里斯塔勒与廖什为代表的代近区位论将经济活动所表现出来的规则性视为理所当然的，对于为什么会产生这样的规则性，人们却不得而知，1990年代，新经济地理学的主要代表人物克鲁格曼将对自组织系统的跨学科研究所取得的成果运用于经济学研究之中，建立起多中心城市的空间自组织模型，他以对厂商之间的向心力和离心力及其相互作用的分析为基础，向我们清楚地阐明了经由一只看不见的手形成大范围内的有规则的经济空间格局的内在机理，即“从不稳定产生秩序”的基本原理。  相似文献   

湘中地区的岩溶发育特征与环境地质问题——以斗笠山,恩口煤矿为例   总被引：4，自引：0，他引：4  

周春光  龚玉红 《湖南地质》1996,15(2):98-102

湘中地区碳酸盐广泛发育，其中含煤向斜盆地的岩溶发育特征，受岩性，地貌，水文，构造运动等多因素控制，并具有水平分带和垂直分带性。而环境地质问题，主要发生岩溶地下水排泄区。  相似文献   

Rock-magnetic proxies of climate change from loess -paleosol sediments of the Czech Republic   总被引：6，自引：0，他引：6  

Eric A. Oches  Subir K. Banerjee 《Studia Geophysica et Geodaetica》1996,40(3):287-300

Summary Rock-magnetic characteristics of late Pleistocene loess-paleosol sequences in the Czech Republic show patterns of variation that reflect climate-related depositional and diagenetic processes which acted on the sedimentary profiles. Mass-normalized magnetic susceptibility is high in interglacial and interstadial paleosols, while uniformly low values are measured in unweathered loess horizons. Normalized ferrimagnetic susceptibility and anhysteretic remanent magnetization show an enhancement of ultrafine (superparamagnetic, SP) and fine (single-domain, SD, and pseudo-single-domain, PSD) grains in chernozem paleosols correlated with δ¹⁸O substages 5c and 5a as well as in the Holocene soil. The parabraunerde paleosol associated with peak interglacial conditions, correlated with δ¹⁸O substage 5e, shows evidence of diagenetic loss of fine grained magnetic minerals, although coarse (multidomain, MD) grains appear to be preserved. Low temperature remanence behavior plus high temperature susceptibility measurements of representative samples from each lithologic unit indicate that magnetite and maghemite are the dominant magnetic minerals within the sediments. Variations in concentration-independent rock-magnetic parameters are therefore primarily a function of grain size variations through the profile. It is anticipated that with additional magnetic and non-magnetic sedimentological and geochemical tests, a quantitative rock-magnetic — paleoclimate model can be developed for the central European loess region.  相似文献   

Ethnic minorities and marginality in the Pamirian Knot: survival of Wakhi and Kirghiz in a harsh environment and global contexts   总被引：1，自引：0，他引：1  

Hermann Kreutzmann 《The Geographical journal》2003,169(3):215-235

This paper challenges the thesis that mountain areas are regions of refuge. The refuge concept attributes irrelevant exchange and limited communication to isolated mountain habitats which mainly depend on production for home consumption. In contrast, it is shown that exchange relations in all walks of life have been affected not only recently but for nearly two centuries in Central Asia, although the continued importance of subsistence strategies in the agricultural sector can be observed. The Pamirian Knot provides the mountainous interface between South and Central Asia for case studies of two ethnic communities – Wakhi mountain farmers and Kirghiz pastoralists – in order to exemplify socio-political developments in similar mountain environments. Examples are presented from Afghanistan, Tajikistan, Pakistan, and the People's Republic of China. The territories have been separated since the late nineteenth century by international boundaries conceived as the result of the imperial 'Great Game'. Emphasis is placed on developments in the livestock sector and it is shown that adaptation to changing socio-political frameworks has affected the livelihood strategies of nomads and mountain farmers alike.  相似文献   

塔中地区中及上奥陶统沉积相   总被引：15，自引：1，他引：15       下载免费PDF全文

张传禄  罗平  魏志彬  马龙  韩宇春 《古地理学报》2001,3(1):35-44

中及上奥陶统是塔中地区主要的油气勘探目的层系之一。在综合地层划分对比的基础上，分析了塔中地区不同沉积相的分布规律。礁滩沉积和斜坡沉积构成了台地边缘相的主体。碳酸盐台地上不同期次发育的边缘相是重要的油气储集体。它们主要分布于塔中I号断裂构造带和TZ10井构造带和塔中南缘断裂构造带上，沉积厚度相对较大。因此，可以得出这样的结论，这种分布状况代表了塔中地区构造对沉积相带的控制作用。通过大量二维及三维地震资料解释分析，发现在塔中广泛分布的丘状隆起地震相、楔状前积反射地震相和杂乱反射地震相相同样多沿主要构造线延伸，内部反射杂乱，成乱岗状反射。把已经认识的沉积相类型和这些地震相的分布特征相比较，可以确定这种地震相就是碳酸盐台地边缘相沉积体。这样，就有可能利用丰富的地震资料，预测有利油气富集的储集体的展布规律。  相似文献   

Characteristics of late Cenozoic volcanism along the Archibarca lineament from Cerro Llullaillaco to Corrida de Cori, northwest Argentina   总被引：1，自引：0，他引：1  

Jeremy P. Richards  Michael Villeneuve 《Journal of Volcanology and Geothermal Research》2002,116(3-4)

The Archibarca lineament is one of several NW–SE-trending transverse lineaments that cut across the Central Andes of Argentina and Chile. Central Andean, Late Miocene–Quaternary subduction-related volcanism is mainly restricted to a 50-km-wide arc forming the approximately N–S axis of the Cordillera, but extends along the transverse lineaments for up to 200 km to the SE. Lineaments are interpreted to be deep-seated, long-lived basement structures or anisotropies, which can control the localization of magmatism and, in some cases, magmatic–hydrothermal ore deposits (e.g., the Escondida porphyry Cu deposit, Chile). As a first step towards exploring the regional-scale controls on magmatism and related mineralization exerted by such structures, the styles of volcanism and near-surface hydrothermal activity along a segment of the Archibarca lineament in the Puna of northwest Argentina are described here. Volcanic structures have been mapped and sampled along a 50-km transect from Cerro Llullaillaco, a large medium-K dacitic Quaternary stratovolcano, to Corrida de Cori, a range of Pliocene–Pleistocene high-K andesitic vents. Apart from a southeastward increase in K content and the predominance of dacitic lavas at Cerro Llullaillaco, the geochemical affinity of late Cenozoic volcanic rocks varies little in time or space. This uniformity extends further SE to Cerro Galán, where published data closely match the results from the study area. In detail, trace element compositions reveal the localized (in both time and space) effects of crustal contamination (recognized as Th>10 ppm), and depth of fractionation (1/Yb>0.7 ppm⁻¹, reflecting garnet residue). Explosive volcanic rocks such as ignimbrites show the strongest indications of crustal contamination, whereas the Cerro Llullaillaco dacite lavas mostly record significant garnet fractionation. Other lavas from the Llullaillaco area, including one flow from Cerro Llullaillaco, do not show garnet control, suggesting that different batches of magma stalled and fractionated at different levels in a thick (60-km) crust prior to eruption. The youngest volcanism in the Corrida de Cori area is represented by olivine–phyric basaltic andesite cinder cones and flows. The ascent of these relatively primitive magmas appears to have been controlled by late Quaternary normal faults, which directly tapped deeply derived melts. The Corrida de Cori volcanic range has experienced intense fumarolic alteration with deposition of abundant sulfate and native sulfur (previously mined at Mina Julia). Deeper levels of hydrothermal alteration have been sampled by an ignimbrite erupted from Cerro Escorial, which, among other lithic clasts, contains numerous fragments of vein quartz. Fluid inclusions in this quartz record evidence for a boiling, high-salinity fluid, which may represent a link between a high temperature magmatic–hydrothermal system at depth (i.e., a porphyry-type system) and shallow-level fumarolic activity. An ignimbrite erupted from Cerro Escorial preserves textures such as internal wave forms between flow units and surface wave morphologies at its distal limits that indicate flow as a series of dense turbulent pulses, which interdigitated and interfered with one another. Lithic lag breccias occur near the base of the flow proximal to the vent, but no air-fall deposits are preserved, probably due to transport of ash far from the vent by strong, high-altitude winds.  相似文献   

塔北-塔中盆地三叠纪陆相层序地层划分及沉积演化   总被引：2，自引：0，他引：2       下载免费PDF全文

傅恒  宋杉林  刘海兴 《沉积与特提斯地质》2002,22(2):31-46

塔里木盆地的三叠纪除早三叠世有短暂的海侵外，其余时间均表现为典型的内陆盆地，发育扇－扇三角洲－湖泊沉积体系。三叠纪的塔里木盆地被北部的沙雅隆起剥蚀区和中、西部的塔中剥蚀区分割成南天山前的库车盆地，昆仑山前的塔西南盆地，阿尔金山前的塔东南盆地和中央的塔北－塔中盆地。前三个盆地的三叠系的残留面积不大，其石油地质意义仅表现在生烃方面。而塔北－塔中盆地的三叠系的残留面积大，构成了塔里木盆地三叠系分布的主体，也成为塔里木盆地油气勘探的主要目的层之一。塔北－塔中盆地的三叠系包含了长周期、中周期和短周期三个级别的基准旋回，其包含有由不整合限定Ⅰ、Ⅱ两个长周期，长周期Ⅰ中可识别一个中周期（Ⅰ1）；长周期Ⅱ中可识别出三个中周期（Ⅱ1，Ⅱ2，Ⅱ3）。塔北－塔中盆地三叠系－侏罗系的有利储集相带与中周期低水位体系域关系密切。盆地中三叠系的3套重要含油气储层Ⅲ油组（T2α），Ⅱ油组（T2α)和Ⅰ油组（T3h)，分别对应三个中周期的Ⅱ1，Ⅱ2和Ⅱ3。  相似文献