山东苍山5.2级地震前地震活动特征   总被引：1，自引：0，他引：1  

刘希强  周焕鹏 《地震》1997,17(2):169-174

从小震活动的时空分布以测震学参数的变化出发，分析了苍山地震前地震活动的异常特下，研究结果表明，苍山５．２级地震前出现了地震活动的图像和几种中，短期测震学参数，异常，但无明显短临信息的前震活动。  相似文献   

Dike intrusion associated with the 2000 eruption of Miyakejima Volcano, Japan     

K. Yamaoka  M. Kawamura  F. Kimata  N. Fujii  T. Kudo 《Bulletin of Volcanology》2005,67(3):231-242

The model for the 2000 dike intrusion event between Kozushima and Miyakejima volcano, Japan, was reinvestigated. After the sudden earthquake swarm in Miyakejima volcano, a dike intrusion of large volume was detected by the nationwide GPS network (Geonet). The displacements detected with GPS stations over an area with a radius of about 200 km shows a distribution that is consistent with the dike source being located near Miyakejima volcano.The dike was intruded northwestwards between Miyakejima and the neighboring Kozushima volcano. We searched for the parameters in the models that reproduce the regional displacements due to dike intrusion between Miyakejima and Kozushiima islands. We tested three models, (1) the model with a single dike, (2) the model with a dike and a point dislocation source which represents a creep dislocation source and (3) the model with a dike and a deflation source which represents a magma reservoir. Though all three models can match the horizontal displacements near the source area, model 1 fails to reproduce the regional displacements in the central part of Japan. Both models 2 and 3 can reproduce the regional displacement for horizontal components. Model 3 produces slightly better results than model 2 for vertical components. The balance in the volume budget for models 2 and 3 is also consistent with the observations. These results show that we cannot distinguish between the two models using only GPS observation. As there is no direct evidence for such a large creep or ductile source (corresponds to M7 or more) as proposed in model 2 and the active seismic region migrated back and forth within the linear swarm region, the model with a dike and a deep magma source is preferable. For the deflation point source, we obtained a deflation volume of 1.5 km³ at the depth of 20 km below the dike. An additional ~0.95 km³ of volume loss through caldera collapse and edifice deflation took place at Miyakejima. We conclude that the magma that intruded the dike came in part from below Miyakejima and in part from below the sea floor between Miyakejima and Kozushima, perhaps from reservoirs at the Moho.Editorial responsibility: S Nakada, T Druitt  相似文献   

Mechanism of loading on plates due to explosive detonation     

W. L. Fourney  U. Leiste  R. Bonenberger  D. J. Goodings 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(4):205-217

This paper investigates the various mechanisms and parameters that are responsible for delivering impulse to a vehicle that is unfortunate enough to detonate a buried mine. Small scale tests are used to examine the effects of air blast or ejected sand in imparting impulse to a plate that is located above the surface of the saturated soil that contains the explosive. Parameters such as confinement, stand off distance, depth of burial of the explosive, density of the soil, and saturation level of the soil are also examined.  相似文献   

Intensification of Southern Hemisphere westerly winds 2000–1000 years ago: evidence from the subantarctic Campbell and Auckland Islands (52–50°S)          下载免费PDF全文

Chris S. M. Turney  Matt McGlone  Jonathan Palmer  Christopher Fogwill  Alan Hogg  Zoë A. Thomas  Mathew Lipson  Janet M. Wilmshurst  Pavla Fenwick  Richard T. Jones  Ben Hines  Graeme F. Clark 《第四纪科学杂志》2016,31(1):12-19

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Spatialising the Melanesian Canarium industry: Understanding economic upgrading in an emerging industry among three Pacific small island states     

《Geoforum》2016

This paper examines economic upgrading in the Canarium indicum (Canarium) nut industry in Vanuatu, the Solomon Islands and Papua New Guinea. Canarium is a tree that is indigenous to Melanesia, and has been the subject of several commercialisation attempts since 1988. The paper assesses the outcomes to various actors in the Canarium supply chain from attempts to upgrade industry products and processes by: (1) increasing the available resource in suitable locations; (2) improving nut products and processing techniques; (3) increasing actors’ knowledge and supply chain coordination; and (4) establishing product standards. A two-phase data generation process was implemented. Document analysis and participant observations of industry workshops initiated a set of four economic upgrading interventions that were adaptively implemented. A second stage of workshops and 76 interviews enabled outcomes to be assessed at the project’s end. Findings suggest that a small number of urban-based entrepreneurs benefit and subsequently are lead actors in industry development, but at the expense of benefits being distributed to a larger, more spatially disparate group of smallholder and small commercial growers. These economic upgrading outcomes are circumscribed by core-periphery relations in Pacific small island states and the scale of industry in each country. Thus, spatial inequalities are reproduced through the emerging Canarium industries. We argue that different routes to industry development are required in each country. Development initiatives that capitalise on the benefits of micro-enterprise clusters, joint action and regional institutional arrangements are proposed to overcome the impediments imposed by the particular geographies of Pacific island states.  相似文献   

川滇地区小震群活动与中强地震     

雷素华 《地震研究》1988,(2)

本文对川滇地区自有地方台,网建立以来的21年间记录到的239次小震群进行了研究,发现Ms≥6.7级的强震绝大多数都发生在小震群年频度增高的背景上。并引用了归一化熵值K作为衡量震群序列中能量分布均匀度的特征量,分析了不同K值的震群与中强震发生的对应关系,发现K≥0.8的震群发生与Ms≥5.5的中强震发生的对应率为59.3%;虚报率为40.7%;漏报率约占14%。K<0.8的震群发生满足无震条件的约占56%。以上结果表明,用归一化熵值K≥0.8来区别前兆震群与一般震群,结果没有华北地区的那样显著。在川滇地区,要将所对应的强震震级提高到6.5级,结果才比较好。  相似文献   

小流域水沙耦合模拟概念模型^*   总被引：6，自引：0，他引：6  

包为民 《地理研究》1995,14(2):27-34

小流域水沙耦合模拟概念模型,采用文献[1]、[2]和[4]中提出的概念性坡面产沙、沟蚀产沙、坡面汇沙、沟道汇沙和格林-安普特下渗曲线结构,结合水文学中的概念性汇流计算方法,构成了一个完整的、具有明确物理意义的流域水流、泥沙耦合模拟模型.该模型结构简单,经子洲试验站团山沟三试验场和蛇家沟、团山沟、水旺沟三试验小流域实测资料的模拟检查表明,模型结构合理、效果较好,适合于黄土地区流域.  相似文献   

试论小区地震活动的时间规律     

姚清林  马宗晋 《地震》1995,(2):117-124

为了探讨小区域内地震活动的时间规律。本文在中国大陆选择了11个地点分析其从远古至公元1990年间的破坏性地震（M≥4 3／4）的活动性。因而发现小区的地震活动规律主要表现于以大震为代表的地震活动分期上，破坏性地震的频率、集中程度与阶段性变化上，以及与所在地震区地震活动期的关系上，不同小区的地震活动特征有共性，有类型区别，更有各自的特殊性。  相似文献   

Vertical sedimentation units in a barrier island washover fan     

S. P. Leatherman  A. T. Williams 《地球表面变化过程与地形》1983,8(2):141-150

Overwash is a major component of a barrier island's response to high energy conditions. Examination of the 19-20 March, 1975, storm deposits at Assateague Island, showed that an overwash sequence could be divided into sedimentation units. Interpretation depends upon defining textural and mineralogical combinations that can be logically ordered as a vertical sequence. If the sequence is depositional and formed from a single material, normal grading usually results; if polymineralogical and erosionally truncated, inverse grading with a top layer of heavy minerals can be formed via an in situ sorting process dependent on disturbance depth and overwash influence.  相似文献   

川西地区小震重新定位及其活动构造意义   总被引：59，自引：18，他引：59       下载免费PDF全文

朱艾斓  徐锡伟  周永胜  尹京苑  甘卫军  陈桂华 《地球物理学报》2005,48(3):629-636

使用双差地震定位法对川西地区1992～2002年的13367个小震进行重新定位， 初步分析了地震活动性与地表活动构造的关系及其揭示的构造信息. 重新定位后，地震活动沿活动断裂成线（带）状分布现象非常突出，呈现出与地表活动构造的密切关系：结构简单的单一走滑断层具有上宽下陡的花状结构特征，拉分盆地与逆断裂具有线性而发散的分布式结构特征，逆断裂之下还存在缺震层. 此外，沿活动断裂带地震活动还具有空间分段性，揭示出局部地段存在着隐伏活动断裂和可圈定为地震危险区的地震空区. 震源深度分布显示，川西高原在15～20km的深度范围内普遍存在厚度约5km的缺震层，以高温高压实验结果为基础，通过计算川西地区地壳强度表明，大约14～19km的深度范围花岗岩处于塑性流变状态，说明缺震层的出现具有地壳物质塑性变形基础.  相似文献