长江中下游地震同青藏高原北部地震的相关性     

李蓉川 《地震研究》1990,13(3):246-255

本文对比了1910—1987年发生的长江中下游地震和青藏高原北部地震,发现两者有比较好的对应关系。一般是,青藏高原北部先发生M≥6级地震,而后长江中下游地区发生M≥19/4级地震。对1910年以来的21次地震进行了统计分析,得到复相关系数R=0.74,能够在很高的显著性水平上通过F检验。地震活动在时间、空间、强度上的相关,现代构造运动及应力场等事实表明,长江中下游地震活动可能主要受青藏高原向东的横向推移运动的影响。  相似文献   

鄂北地区碱性岩的时代及成因   总被引：7，自引：2，他引：7  

李石 《岩石学报》1991,7(3):27-36

产于鄂北的花山寨、观子山、杀熊洞和庙垭四个碱性岩体,其K-Ar、U-Pb和Rb-Sr同位素年龄值为215～306Ma,成岩时代属海西—印支期。根据~(87)Sr/~(86)Sr初始值,杀熊洞岩体(0.7032)和庙垭岩体(0.7029)的成岩物资来源于上地幔,观子山岩体(0.7041)的成岩物质属幔壳混源型,但仍以幔源为主,花山寨岩体(0.7092)的成岩物质则主要来源于下地壳。  相似文献   

北半球增暖对我国气侯的影响     

屠其璞 《南京气象学院学报》1991,(3)

本文在分析100多年来北半球平均气温长期变化基本特征的基础上,讨论了北半球气温变化对我国气候变化的影响。结果表明,我国大范围气温距平与北半球平均气温有显著的正相关,长江中下游和华北平原的温度距平值平均为北半球平均气温距平的1.4-1.6倍。还表明,我国降水距平分布与北半球气温变化也有一定的联系。在北半球平均气温偏高和偏低年份,欧亚地区500hPa环流特征的差异是显著的。这表明,我国大范围气候距平与北半球平均气温距平的统计相关是有一定的物理基础的。  相似文献   

西秦岭北缘断裂带新活动特征   总被引：27，自引：2，他引：27       下载免费PDF全文

滕瑞增  金瑶泉  李西候  苏向州 《地震工程学报》1994,16(2):85-90

在本文中，作者在近几年进行的大比例尺活断层地质填图工作的基础上，介绍了西秦岭北缘断裂带晚第四纪以来活动的基本待征，研究了该断裂带的空间展布情况、几何学和运动学特征、断层活动速率、古地震与地震重复周期等。结果表明，该断裂带自第四纪以来由压性逐渐演变为左旋扭动，其水平滑动速率为２．１－２．８ｍｍ／年，垂直滑动速率为０．４－０．７ｍｍ／年，地震复发周期约为５０００年。  相似文献   

安徽大别山北部红刚玉岩石的成因     

孙先如  周作祯 《岩石学报》1994,10(3):275-289

大别山北部红刚玉矿产在太古代大别山群黑云角门外长片麻岩以及超基性岩中。赋存红刚玉的刚玉黑云二长片麻岩的原始岩石为富铝泥质岩，在角门岩相变质条件下，通过两种脱硅方式，即变质分异作用和超基性岩侵位，形成刚玉黑云二长片麻岩。它们形成的温压条件：Ｔ＝５００℃～７００℃，Ｐ＝０．４～０．７ＧＰａ。刚玉形成的可能的化学机制是白云母在缺硅条件下的分解。  相似文献   

Fire and cyclone damage to woody vegetation on the north coast of the Northern Territory,Australia     

D.M.J.S. Bowman  W.J. Panton 《The Australian geographer》1994,25(1):32-35

Tree stem (>2 m tall) mortality was assessed following a late dry‐season wildfire across a seasonally flooded elevation gradient at Workshop Jungle, near Darwin, in the Northern Territory of Australia. For all species combined, dead stems had significantly smaller diameter at breast height (dbh) than living stems. Assessment of tree‐stem damage following a tropical cyclone at Cobourg Peninsula, NT, revealed that damaged stems had significantly greater dbh than undamaged stems for all tree species sampled across a boundary between monsoon rainforest and savanna. A greater proportion of stems were damaged by the cyclone than by the fire (28 per cent as against 18 per cent), although there were considerable between‐community differences in the proportion of damaged stems at the two sites. The fire caused little impact (<10 per cent) on total basal area of three different forest communities on the elevation gradient at Workshop Jungle. The cyclone was found to cause >50 per cent damage to total basal area of three different communities on Cobourg Peninsula. It is suggested that the combination of a cyclone followed by an intense fire in storm debris could potentially destroy a monsoon rainforest through its impact on all tree‐size classes. This may explain why some monsoon rainforests rapidly contracted following Cyclone Tracy that destroyed the city of Darwin on Christmas Day, 1974.  相似文献   

吉林省北部A型花岗岩的初步认识   总被引：2，自引：0，他引：2  

石新增  李树田 《吉林地质》1995,14(2):64-70

分布在吉林省北部的香水、治安一带的正长花岗岩、碱长花岗岩，研究后认为属Ａ型花岗岩。其行征钾长石为微斜长石一条纹长石，斜长石大部分为奥长石Ａｎ＝１３－１７。并有碱性碱物无辉石。  相似文献   

塔里木盆地北部构造样式   总被引：10，自引：0，他引：10       下载免费PDF全文

严俊君  黄太柱 《地球科学》1995,20(3):264-270

塔里木盆地北部发育５种典型的构造样式；基底卷入型压性逆冲构造组成、盖层滑脱型逆冲－褶皱构造组合、隐刺穿刺底檗同幅度褶皱构造组合及张性正断层组合，无论是构造变形时间还是组合分布，在塔北均呈现规律变化，其变形特征及发布受如下３个地质因素控制：（１）区域挤压作用；（２）岩性条件的差异：（２）先期构造格局。  相似文献   

塔里木盆地北部油气田水文地质及水文地球化学特征   总被引：1，自引：0，他引：1       下载免费PDF全文

张建林  陶一川  陈荣书  张忠先 《地球科学》1995,4(3)

以实测的流体资料为基础，初步揭示了塔北地区油田水文地质和水文地球化学特征。塔北地区存在两股地下水流，南部生油区为压实水流，由南向北流动，北部为重力水流，由北向南流动，这两股水流交汇于雅克拉和轮南地区，向上封闭式内泄。无论重力水流或压实水流，皆为非海相成因、非浓缩成因溶滤水。表明：油气藏的形成绝大部分是寒武－奥陶纪生油层二次成油的结果。  相似文献   

Gravity and magnetic expression of the concealed basic and ultrabasic bodies in Chalkidhiki,Northern Greece     

Gregory N. Tsokas 《Pure and Applied Geophysics》1995,144(1):117-134

The anomalies which are shown on the gravity and aeromagnetic data of the Chalkidhiki peninsula of Northern Greece reveal the presence of three concealed dense and magnetized bodies. The ophiolitic belt which continues northwards of the geophysical anomalies suggests that they are caused by structures which belong to it. Multiple source Werner deconvolution shows that the lower surfaces of buried bodies in Toroneos Gulf and the one onshore are concave upwards. The northern concealed body has a width of 16 kilometers, while the southern one is 8 kilometres in width. A three-dimensional model, well constrained, gives an estimate of the dimensions of the onshore feature. The edges of the bodies, delineated by the terracing method, are formed by faults along the trend of the Hellenides orogenic belt. The edges of the body in the outer part of Toroneos Gulf may be associated with seismic swarms that occurred in the 1980s.  相似文献