Clast Fabric in Relict Periglacial Colluvium, Salamanca Re-Entrant, Southwestern New York, USA     

Susan W.S. Millar  & Frederick E. Nelson 《Geografiska Annaler: Series A, Physical Geography》2001,83(3):145-156

Samples of macrofabric data obtained from colluvial deposits near the late-Wisconsinan glacial margin display widely divergent characteristics. Those from highly weathered and jointed sandstone plot as girdle distributions. Samples from red colluvium of early-Wisconsinan age form moderately strong clusters. Fabrics from shallow depth in medium-textured brown colluvium of late-Wisconsinan age generally have modes aligned with the local slope but are weak, and appear to have been modified by frost heaving. Clasts in the basal layers of an overlying loess unit were emplaced by frost heaving from the brown colluvium and have very weak or uniform fabrics. Particle shape exerts an influence on fabric strength in the brown colluvium, with samples composed of more elongated clasts displaying stronger fabrics. Fabrics from near-surface deposits show generally weaker shape and strength characteristics and higher inclinations than those at depth. Calculated seasonal frost penetration is consistent with the depth to which weaker, more steeply inclined fabrics are found. Sampling in relict periglacial deposits should be performed only below the level of disturbance by seasonal frost.  相似文献   

Negative Dislocation Model and the Movement Pattern of a Fault:Determination of Potential Earthquake Sources in Western Yunnan     

Wu Jicang  Gao XimingInstitute of Seismology  SSB  Wuhan  China 《中国地震研究》1995,(4)

To determine the locked and slip parts on a fault,we simulated the movement pattern of the fault with a combined model consisting of a negative dislocation in the locked area superimposed on a relative movement between two sides of the fault.In this way,we determined the locked parts of faults by inversion with multiple epochs of geodetic data.In this paper,we have determined the movement patterns of four main faults in western Yunnan by inversion with two epochs of geodetic surveys and some crossing-fault observations.From the inversion result,we have identified the areas around Dali and Xiangyun to be the locked area,which is regarded as a sign of potential earthquake sources.  相似文献   

东南沿海末次盛冰期古海平面标志与地震的关系──-100m以下最低海平面问题质疑   总被引：1，自引：0，他引：1  

徐起浩  黄镇国 《地震地质》1995,17(2):149

东南沿海末次盛冰期（２１～１４ｋａＢ．Ｐ，）滨海相沉积垂相分布多在海拔３８～－５０．８ｍ的范围内，以正向分布（海平面附近及以上）、正负向混合分布及负向（海平面以下）分布在断块交界区或其附近，是强震的主要发生地。在滨海相沉积垂向分布愈离散的区段，其地震活动性也愈强，本研究地区不存在末次盛冰期－１００ｍ以下的最低海平面，那些局部在外陆架海底发现的－１００ｍ以下的滨海相沉积，可能与地壳呈长趋势下沉作用有关  相似文献   

Study　on　the　pattern　and　mode　of　vertical　crustal　deformation　during　the　seismogenic　process　of　intraplate　strong　earthquakes   总被引：3，自引：0，他引：3  

杨国华  桂昆长  巩曰沐  杨春花  韩月萍  孙东平 《地震学报(英文版)》1995,8(2):195-204

Ｓｔｕｄｙｏｎｔｈｅｐａｔｔｅｒｎａｎｄｍｏｄｅｏｆｖｅｒｔｉｃａｌｃｒｕｓｔａｌｄｅｆｏｒｍａｔｉｏｎｄｕｒｉｎｇｔｈｅｓｅｉｓｍｏｇｅｎｉｃｐｒｏｃｅｓｓｏｆｉｎｔｒａｐｌａｔｅｓｔｒｏｎｇｅａｒｔｈｑｕａｋｅｓ杨国华，桂昆长，巩曰沐，杨春花，韩...  相似文献   

台风移动规律的研究　Ⅲ.台风与外界水平动量交换的影响     

贺海晏  董惠菁 《热带气象学报》1995,(3)

着重分析了流场半非对称台风的流入层和流出层与外界的水平动量交换影响台风移动的定性特征。结果表明，主要流入通道或主要流出通道位于台风右（左）侧时，有利于台风加速、左折（减速、右折）；当主要流入通道或主要流出通道位于台风后部（前部）时，有利于台风加速、右折（减速、左折）。  相似文献   

GIS数字曲线复杂性的度量与误差建模中趋势项的分离     

刘文宝  黄幼才  李宗华 《武汉大学学报(信息科学版)》1995,(4)

引入了衡量ＧＩＳ数字曲线复杂性的四种指标，提出了误差建模中趋势项分离的样条函数法，考察了分离一组具有不同复杂度模拟曲线的有效性，并与差分法进行了比较。  相似文献   

冀西北水晶屯金矿金及其指示元素的水平分带特征   总被引：1，自引：0，他引：1  

魏俊浩 《黄金地质》1995,1(1):51-54

对水晶屯金矿的地质特征进行了简要介绍，选择了对找金具有指示意义的８种元素，Ａｕ，Ａｓ，Ｓｂ，Ｈｇ，Ａｇ，Ｐｂ，Ｍｏ，Ｂｉ。详细讨论了金及其指示元素泊水平分带特征，这对评价该矿床的剥蚀程度，深部含矿性具有指导意义。  相似文献   

中国东部中亚构造带及向环太平洋构造带的转化   总被引：4，自引：0，他引：4  

王东方 《华北地质矿产杂志》1995,10(2):135-142

中亚古亚洲洋的消失可由该地区大量晚元古后期－泥盆纪残余洋壳和高压变质带的存在来说明，其中大量８００～５５０Ｍａ蛇绿岩和高压变质带说明兴凯运动是主要造山期。加里东和华力西造山运动是其后续运动，早石炭世是一个转折期，早石炭世地层基本缺失，洋壳残片不再出现，变质作用突然减弱，表明中亚地区构造机制已逐渐转入大陆内部。石炭二叠纪地壳开始拉伸，形成了晚古生代裂谷并产生强烈岩浆作用。二叠纪末。早中生代全区隆起，残余海盆地消失，西伯利亚地台以其盾形前缘向南推移，形成推土机机制改变了加里东－华力西期的东西向构造格局，形成折接的类弧形构造，其东部为北东向构造，前缘为东西向，西部为北西向，总体形成宏伟的推覆断层及走滑断层系，早中生代中国东部环太平洋构造带以南北向为特征，由东而西的侧压力转换成剪切分量，加强了北东向的走滑和拖曳。在这一过程中，环太平洋构造以最接近的应力场和最低的地动能消耗、制动，继承和改造了晚末期中亚构造系，达到两个大地构造区系的交替和过渡。  相似文献   

泛华夏大陆群与东特提斯构造域演化   总被引：5，自引：1，他引：5       下载免费PDF全文

李兴振  许效松  潘桂棠 《沉积与特提斯地质》1995,(4):1-13

本文以板块构造理论为基础,根据全球各大陆陆块和微陆块的相对亲缘性、统一性和独立性,提出晚前寒武纪末一早古生代初泛大陆解体后,整个古生代期间,全球大陆可划分为三大陆块群,即冈瓦纳大陆群、劳亚大陆群,和泛华夏大陆群。论述了三大陆块群,特别是泛华夏大陆群的形成演化及其作为独立大陆群存在的统一性。指出泛华夏大陆群的独立性和统一性表现在:①早古生代末,扬子、华夏(包括黄海一东海一南海古陆)、中朝、柴达木、塔里木、昆仑一北羌塘一昌都一印支等陆块曾一度拼贴在一起,形成统一的大陆;②晚古生代中晚期形成独立的华夏植物群区系;③晚古生代末一早中生代,泛华夏大陆群主体部分的扬子一华夏和中朝陆块向西运移楔入,导致其南北两侧古特提斯洋的同步消亡和全球泛大陆的最终形成。泛华夏大陆群的形成演化历经了晚前寒武纪末一早古生代初各陆块的裂离、割据;早古生代末的拼贴、统一;晚古生代的再次分裂和晚古生代末一早中生代与南北大陆群拼贴4个发展阶段。同时指出在东特提斯构造域内,古特提斯既表现出对原特提斯的继承性,又有新生性;中特提斯不是古特提斯的延续和发展,它是标志泛大陆裂一聚巨旋回演化中另一旋回的开始。最后讨论了显生宙地球上大陆由南聚北散到北聚南散,陆块在总体上向北漂移中旋转、裂、聚和泛大陆重组和立即又解体的可能的动力学机制,即地球内部物质向南半球运移,南半球膨胀,促使泛大陆解体。地球内部物质的南移又迫使软流层物质向北运动,驱动大陆碎块北上。蠕动的软流层中,除具有垂向环流的对流环外,还具有大小不等的水平涡旋运动。正是巨大的水平涡旋运动导致了陆块的旋转、会聚(泛大陆形成)和很快脱离涡旋体面离散(泛大陆解体)。  相似文献   

Current crustal motion and deformation in the Chinese mainland and its surrounding area determined from GPS data   总被引：1，自引：0，他引：1  

YUN WU  PING SHUAI  SHUO-YU ZHOU 《地震学报(英文版)》1999,12(5):596-606

Based on the geodetic data taken from the National GPS Network established by China Climbing Program "Investigation of Crust Motion and Geodynamics in Modern Time",we derived the movement velocities of the GPS sites. In terms of the power series expansion of a rotation function for horizontal velocities on a spherical surface proposed by Haines and Holt (1993), we computed the horizontal velocity and strain-rate field. We preliminarily studied the appearances and characteristics of the present-day crustal movement and deformation in the Chinese mainland with the computed results. The researches demonstrated: ① The present-day crustal movement and deformation in the Chinese mainland are being jointly controlled by Indian, Pacific and Philippines Ocean Plates and Siberia-Mongolia block, and these three large plates and block form a situation of tripartite confrontation, but Indian Plate seems to play a leading role; ② The North-South Earthquake Zone plays an important adjustment role in the present-day crustal movement and deformation process, displaying clear characteristics of demarcation line of tectonics in large areas; ③ There seems to be another adjustment zone along the latitude line approximate N35°, but its characteristics are less obvious than that of the former; ④ Dynamic actions of these three large plates and block on the Chinese mainland are dynamic stable; appearing in stable push-press velocities. These results are generally accorded with the results determined from geology, geophysics, and seismology. By the contrast with seismicities, it appears preliminarily that there is some corresponding relation between intense shear strain zone and future strong seismicity area, but this problem needs further examination of earthquake examples.  相似文献