宝鸡市地质灾害特征及形成主要因素分析

介绍了宝鸡市地质灾害的类型、规模及特征,并着重分析了宝鸡市地质灾害形成的主要因素。认为虽然造成区内地质灾害发生的因素甚多,但近年来大多与人为因素诱发有关。因此,在国土开发和国民经济建设中,应重视对地质环境的保护,避免因人类不适宜的活动而诱发地质灾害。     

Mechanical intrusion models and their implications for the possibility of magma-driven swarms in NW Bohemia Region

Earthquake swarms are often assumed to be caused by magmatic or fluid intrusions, where the stress changes in the vicinity of the intrusion control the position, strength and rate of seismicity. Fracture mechanical models of natural intrusions or man-made hydrofractures pose constraints on orientation, magnitude, shape and growing rate of fractures and can be used to estimate stress changes in the vicinity of the intrusions. Although the idea of intrusion-induced seismicity is widely accepted, specific comparisons of seismicity patterns with fracture models of stress changes are rarely done. The goal of the study is to review patterns of intrusion-induced earthquake swarms in comparison to the observations of the swarm in NW Bohemia in 2000. We analyse and discuss the theoretical 3D shape of intrusions under mixed mode loading and apparent buoyancy. The aspect ratio and form of the intrusion is used to constrain parameters of the fluid, the surrounding rock and stress. We conclude that the 2000 NW Bohemia swarm could have been driven by a magmatic intrusion. The intrusion was, however, inclined to the maximal principal stress and caused shear displacement additional to opening. We estimate that the density diference between magma and rock was small. The feeding reservoir was possibly much larger than the area affected from earthquakes and may be a vertical dike beneath the swarm region.     

成组中强震前后动态小震的时空活动特征

分析了进入活跃时段以来,新疆及邻近地区自１９９５年３月１９日和硕Ｍｓ５．０地震后,相继发生的１２次Ｍｓ≥４．７地震前后调制小震和动态小震的时空活动特征,据此提出了孕系统失稳模式;     

Preliminary investigation of seismic damage to two steel space structures during the 2013 Lushan earthquake

Severe damage to steel space structures is rarely reported when compared to other structural systems damaged during past major earthquakes around the world.Two gymnasiums of steel space structures in downtown Lushan County that were damaged during the 2013 M7.0 Lushan earthquake in China were investigated and the observations are summarized in this paper.Typical damage to these two steel space structures ranges from moderate to severe.Moderate damage includes global buckling and dislocation of bolted connections of truss members,and inelastic elongation of anchor bolts and sliding of pedestal plates of supports.Severe damage includes member fracture caused by local buckling,and fracture failure of anchor bolts and welds.The distribution of structural damage to these two structures is described in detail and future research opportunities are suggested.     

Rates of cave and landform development in the Yorkshire Dales from speleothem age data

Uranium-series ages have been obtained for 87 speleothems collected from nine major cave systems in the Craven district of northern England. Large systems such as Ease Gill Caverns, the West Kingsdale caves, and Gaping Gill-Ingleborough Cave, which contain relict high-level tunnels, are found to be older than 350,000 years (the limit of the ²³⁰Th/²³⁴U dating method). There is little evidence to indicate a significant enlargement of these passages since this time. Estimates of the age of Victoria Cave from ²³⁴U/²³⁸U isotopic ratios suggest that the cave has been fully relict for more than 500,000 years. Ages of in situ speleothems immediately adjacent to local base level cave streams show that mean maximum downcutting rates in limestone channels are about 2 to 5 cm 1000 yr. These rates are significantly lower than those obtained from direct measurements on limestone bedrock in stream channels but are comparable to areal denudation rates based on solute budgets. Using the present elevation of caves with respect to adjacent valley floor levels, mean maximum valley entrenchment rates are found to range between 5 cm/ky and < 20cm/ky, which corresponds to 6 m to < 24 m of lowering per glacial/interglacial cycle. These rates suggest that upper beds of the limestone were incised to form the Yorkshire Dales between 1 and 2 million years ago. The results indicate that the erosional effects of individual glaciations are not as severe as previously proposed in the literature.     

第20届国际大地测量学与地球物理学联合会维也纳大会地震地质类成果交流简介

根据作者参加大会收集到的资料和考察体会，介绍了在会上交流的地震地质类成果，对某些前缘研究领域的新进展作了重点介绍。     

断裂系扩展过程与地球物理场变化特征的实验研究

给出了判断断裂之间有无相互作用的力学判据.为了研究断裂间相互作用对地球物理场的影响,对若干类常见断裂系的扩展过程及扩展过程中的声发射b 值和波速变化进行了模拟实验研究.结果表明,各种断裂系由于相互作用的不同,扩展过程,声发射b 值和波速度化均有明显的不同特征.     

具有立交成因重复地震的有限元分析

应用有限元分析方法 ,分析计算了具有立交成因的原地重复地震的孕育机理 ,得出如下结论 :在第一个地震临震前 ,与发震断层平行立接的深部断层对发震断层有底劈作用 ,发震后深部断层会继续破裂传播 ,导致浅层的横向断层扭曲 ,从而使横向断层闭锁而孕育地震。     

A modeling study on the controlling factors of seismic source distribution and their strength index——Practical analyses of the seismic environmental factors of the Honghe fault

IntroductionThe tectono-physical background and dynamic environmental features of strong earthquakes have long been studied from different viewpoints by seismologists both in domestic and abroad. Many controlling factors include the crust structure, lithological environment, tectonic conditions, the stress state, heat flow distribution and hydrodynamic effects at depth, etc. Some of the studies have established a foundation for researching and recognizing the spatial distribution of potential …