地震共中心点道集的滑动基准面静校正和动校正叠加理论模型计算和分析   总被引：4，自引：1，他引：3  

刘江平  钱绍瑚  张素新 《物探与化探》1998,22(1):27-33

本文通过对两个典型地形起伏的四个水平界面理论地质模型的计算和分析,进一步阐明了在复杂地形条件下用常规水平基准面静、动校正方法进行反射波法多次覆盖,不仅达不到较为理想的多次覆盖的目的,反而使之同相轴发生畸变并产生假的同相轴特征的主要原因及该方法所存在的问题;证明了滑动基准面静、动校正叠加方法在复杂地形地区从事地震反射波法多次覆盖技术勘探的有效性、实用性和可操作性。  相似文献   

前寒武纪的超大陆旋回及其板块构造演化意义   总被引：13，自引：1，他引：12  

李江海 《地学前缘》1998,(Z1)

太古代末早古生代存在４次超大陆或大陆聚合时期,超大陆的聚合与裂解造成全球性的重大构造热事件,成为全球板块构造演化的主线,威尔逊旋回在早前寒武纪已明显起作用。超大陆的聚合表现为克拉通的增生与陆块的碰撞造山作用;超大型的裂解表现为非造山岩浆活动、大规模基性岩墙群侵位及大陆裂谷的爆发等。超大陆的裂解可能与地幔柱上涌或超大陆下放射性物质积聚造成的热能积累有关,或地外物质冲击的触发有关。华北克拉通与世界古陆块的前寒武纪构造演化对比,及其在超大陆中的拼合模式成为我国大陆地质学研究面临的挑战性重大科学问题。  相似文献   

黄河下游花园口河段洪水涨落过程中河床横断面形态的调整          下载免费PDF全文

张欧阳  许炯心  张红武 《水科学进展》2003,14(4):401-406

利用黄河下游1950-1985年间218场洪水资料,讨论了黄河下游花园口河段洪水起涨和回落过程中河床形态调整的不同过程.在洪水起涨阶段,花园口河段河床宽深比以增大为主,且洪水最大含沙量越大,宽深比增大的幅度越大,洪峰增幅比在3以下时,宽深比随最大含沙量的增大而增大,洪峰增幅比在3以上时,呈随含沙量的增大而减小的趋势.在洪水回落阶段,宽深比的变化方向则相反.在含沙量较小时,河床宽深比的减小主要发生在洪水起涨阶段,在含沙量很大时,河床宽深比的减小主要发生在洪水回落阶段.  相似文献   

Research on the multifractal characteristics of the temporal—spatial distribution of earthquakes over New Zealand area     

陈时军  David Harte  马丽  王丽凤 《地震学报(英文版)》2003,16(3):312-322

Using the Hill estimator,general multifractal characteristics of events in the New Zealand area have been dis-cussed.Results show that the spatial distribution of shallow events has apparent clustering characteristics,inde-pendent of the threshold magnitude;but for deep events these characteristics are not clear.While the time interval distribution has obvious clustering characteristics both for deep and shallow events,although with a different scal-ing range,the Hill estimates tend to indicate that the time interval distribution has a unifractal rather than a multi-fractal nature.All above reveal that the seismicity nature for shallow and deepevents is apparently different.  相似文献   

通化二密铜矿周边中生代火山岩系基本特征及找矿方向   总被引：4，自引：0，他引：4  

刘兴桥 《吉林地质》2003,22(1):8-13

通化地区是吉林省中生代火山岩广泛发育的地区之一,伴随着火山作用形成的矿产资源十分丰富,尤以贵金属和多金属矿产居多,二密铜矿即是其中典型矿床之一,其周边地区相关火山岩系可划分为三期火山事件,并具有钙碱性向碱性火山岩系演化特点。事实上整个火山作用过程亦是一个成矿过程,但晚期火山事件的成矿作用应引起重视,是进一步找矿的主要方向之一。  相似文献   

Storm Surge Hazard in Canada   总被引：3，自引：2，他引：3  

Maurice Danard  Adam Munro  Tad Murty 《Natural Hazards》2003,28(2-3):407-434

Storm surges occur frequently in Canada mainlydue to extra-tropical cyclones (ETC'S) also referred to as winter storms. The hurricanes from the Gulf of Mexico can affect eastern Canada including Lakes Ontario and Erie regions, after they get modified and acquire some extra-tropical characteristics. Storm surges have occurred both on the Atlantic and Pacific coasts, in the Gulf of St.Lawrence, St.Lawrence Estuary, Bay of Fundy, Hudson Bay, James Bay, Northwest Passage, Beaufort Sea, the Great Lakes and other large lakes such as Lake Winnipeg.Squall lines which are embedded in the largerscale synoptic systems like the ETC'S could also generate storm surges (referred to as edge waves) in Lakes Huron, Erie and Ontario (edge waves are most prominent in Lake Michigan, but Canada has no territory touching this lake). The effect of climate change on storm surges in the Canadian water bodies could be two-fold. First, there may be some possible intensification of the weather systems and the associated wind fields resulting in bigger surges. Second, and probably even more relevant, is an east-west and north-south shift in the tracks of the weather systems, which could expose certain new areas to storm surge activity.A high priority for proper assessment of storm surge hazard is the production of maps showing inundation zones for storm surges that might occur in populated coastal areas. Such maps can be used to improve public awareness of tsunamis and for planning purposes (i.e., to reduce or avoid the risk).  相似文献   

On the ages of flood basalt events   总被引：2，自引：0，他引：2  

Vincent E Courtillot  Paul R Renne 《Comptes Rendus Geoscience》2003,335(1):113-140

We review available data constraining the extent, volume, age and duration of all major Phanerozoic continental flood basalts (CFB or traps) and oceanic plateaus (OP), together forming the group of large igneous provinces (LIP), going from the smallest Columbia flood basalts at ～16 Ma to the as yet ill-known remnants of a possible trap at ～360 Ma in eastern Siberia. The 16 traps (CFB and OP) reviewed form a rather unimodal distribution with an initial modal volume of the order of 2.5 Mkm³. Most provinces agree with a rather simple first order model in which volcanism may have lasted of the order of 10 Ma, often resulting in continental break-up, but where most of the volume was erupted in about 1 Ma or sometimes less. This makes CFBs/OPs (LIPs) major geodynamic events, with fluxes exceeding the total output of present day hot spots and even possibly exceeding over short times the entire crustal production of mid-ocean ridges. The proposed correlation between trap ages and the ages of several geological events, including mass extinctions and oceanic anoxia, is found to have improved steadily as more data have become available, to the point that the list of trap ages may coincide with many major divisions in the geological time scale. The four largest mass extinctions in the last 260 Ma coincide to the best resolution available with four traps, making a causal connection between the two through some form of catastrophic climatic perturbations the most likely hypothesis. The time sequence of LIPs appears to have been random and there is no robust evidence for long time trends in the corresponding crustal production rate over the last 260 Ma.  相似文献   

A 2.8 Ma record of environmental evolution and tectoni events inferred from the Cuoe core in the middle of Tibetan Plateau     

SHEN Ji  Lü Houyuan  WANG Sumin  CHEN Shiyue  YANG Xiangdong  WU Yanhong & ZHU Zhaoyu .Nanjing Institute of Geography  Limnology  Chinese Academy of Sciences  Nanjing  China  .Institute of Geology  Geophysics  Chinese Academy of Sciences  Beijing  China  .Guangzhou Institute of Geochemistry  Chinese Academy of Sciences  Guangzhou  China Correspondence should be addressed to Shen Ji 《中国科学D辑(英文版)》2004,(11)

The uplift of the Tibetan Plateau is the most im-portant event in the Cenozoic Era. It has been provedthat the rising Plateau is of great significance to globalatmospheric circulation and climate change. It has alsoinfluenced the transmission and balance of the globalmatter and energy[1—3]. The uplift of the Plateau is un-doubtedly true, but there have long been argumentsabout the process and mode of the Plateau uplift. Didthe Plateau rise as a whole or partly? Did it rise oncefor all or …  相似文献   

东特提斯二叠—三叠纪事件概述     

Swee.  WC 杨遵仪等 《现代地质》1992,6(4):373-383

本文译自《东特提斯二叠—三叠纪(P/T)事件》(英文本)第一章,包括六方面内容:(1)生物地层学,利用腕足类、菊石类、牙形石和植物,建立P/T界线间隔的生物地层表;(2)地球化学研究,讨论目前可用资料,绘出P/T界线间隔的δ~(13)C和δ~(16)O剖面;(3)古地磁研究,借以决定同一界线间隔的划分;(4)火山作用,大多数作者用火山成因解释P/T界线间隔;(5)生物更替原因,包括主要的海侵,广泛的火山作用和火流星的溅射;(6)多方面证据说明P/T界线最好划在Changxingensis带和Isarcica带之间。  相似文献   

Mining-induced microseismic event location errors: Accuracy and precision of two location systems     

P. L. Swanson  L. H. Estey  F. M. Boler  S. Billington 《Pure and Applied Geophysics》1992,139(3-4):375-404

The accuracy and precision of microseismic event locations were measured, analyzed, and compared for two types of location systems: anolog and digital. In the first system, relative times of first arrival were estimated from analog signals using automated hardware circuitry; station positions were estimated from mine map coordinates; and event locations were determined using the BLD (Blake, Leighton, and Duvall) direct solution method. In the second system, arrival times were manually measured during interactive displays of digital waveforms; station coordinates were surveyed; and the SW-GBM (Salamon and Wiebols; Godson, Bridges, and McKavanagh) direct basis function was used to solve for locations. Both systems assume constant isotropic seismic velocity of slightly different signals data sets, calibration blast signals with known source site and origin time, and microseismic event signals, were recorded by each location system employing the same array of high-frequency (5 kHz) accelerometers with 150 m maximum dimension. The calibration blast tests indicated a location precision of ±2 m and accuracy of ±10 m for the analog system. Location precision and accuracy for the digital system measured ±1 m and ±8 m, respectively. Numerical experiments were used to assess the contributions of errors in velocity, arrival times, and station positions on the location accuracy and precision for each system. Measured and estimated errors appropriate to each system for microseismic events were simulated in computing source locations for comparison with exact synthetic event locations. Discrepancy vectors between exact locations and locations calculated with known data errors averaged 7.7 and 1.4 m for the analog and digital systems, respectively. These averages are probably more representative of the location precision of microseismic events, since the calibration blast tests produce impulsive seismic arrivals resulting in smaller arrival-time pick errors in the analog system. For both systems, location accuracy is limited by inadequate modeling of the velocity structure. Consequently, when isotropic velocity models are used in the travel-time inversions, the increased effort expended with the digital location system does not, for the particular systems studied, result in increased accuracy.  相似文献