地球弓激波前的低频磁流体波     

李少峰  孙炜 《地球物理学报》1990,33(2):239-241

一、引言 在地球弓激波前存在着低频磁流体波。这种低频磁流体波是太阳风在地球弓激波上的反射粒子和太阳风粒子之间相互作用产生的。根据人造卫星的观测资料可以得到,在地球弓激波前,Pc3-4脉动频率范围内的低频磁流体波的主频率和行星际磁场强度  相似文献   

强震前电磁波异常观测研究   总被引：1，自引：0，他引：1  

林美  李开复 《地震研究》1990,13(4):353-360

本文报导了1981年以来,特别是1985年以来架设于楚雄观测站的电磁波接收器记录到的电磁波异常现象。后出,1985年一1987年4月停记前,以观测站为中心,400公里为半径范围内,发生了18次M_L>5.0级地震,有15次地震前记录到明显异常(其余3次异常不太明显,当作无异常)。结果表明,电磁波异常观测是一种有希望的临震预报手段。  相似文献   

电磁波井间CT成象技术及其在岩土工程中的应用     

邱陶兴  陶裕录 《华南地震》1994,14(3):16-23

简要叙述了电磁波ＣＴ成象技术的基本原理、工作方法及其在岩土工程中诸如机场跑道、隧道工程和高层建筑地基评价中的应用。通过井下激发和观测电磁波能量的衰减，利用ＣＴ技术重建了地下介质在观测平面内相对吸收系数的二维分布图象，这些图象直观准确地反映出地下介质的构造形态、地层界面、风化壳以及破碎带的分布特征，在岩土工程探测中发挥了重要作用。  相似文献   

位于导电介质中三维导体的电磁响应          下载免费PDF全文

靳职理  许洪海 《地球物理学报》1989,32(4):423-432

本文给出一种用积分方程法配合有限差分法计算位于导电介质中三维导体的电磁响应的新途径,在二层大地条件下给出了具体计算方法和结果。详细讨论了围岩介质的导电性对导体异常的影响。这对于开展低阻覆盖层地区的电磁法工作具有一定的指导意义。  相似文献   

青海省地震电磁辐射监测     

哈辉 《高原地震》1995,(2)

本文概述了青海省电磁辐射台网的建设、台网特征、台网管理及映震效能。  相似文献   

A new technique for determining the surface level of salt marshes and other uncompacted sedimentary environments     

Alan P. Carr 《地球表面变化过程与地形》1983,8(3):293-296

The method described involves the use of an electro-optical distance measurer mounted on a theodolite. Observations are taken onto a series of acrylic reflectors, aligned at right angles to the line of sight, and slope distances and vertical and horizontal angles are recorded. From these data it is possible to obtain surface heights to an accuracy of ±0·5 cm at 200 m and to avoid any direct disturbance of the site under investigation.  相似文献   

Inverted-polarity electrical structures in thunderstorms in the Severe Thunderstorm Electrification and Precipitation Study (STEPS)     

W. David Rust  Donald R. MacGorman  Eric C. Bruning  Stephanie A. Weiss  Paul R. Krehbiel  Ronald J. Thomas  William Rison  Timothy Hamlin  Jeremiah Harlin 《Atmospheric Research》2005,76(1-4):247

Balloon-borne electric field soundings and lightning mapping data have been analyzed for three of the storms that occurred in the Severe Thunderstorm Electrification and Precipitation Study field program in 2000 to determine if the storms had inverted-polarity electrical structures. The polarities of all or some of the vertically stacked charge regions in such storms are opposite to the polarities observed at comparable heights in normal storms. Analyses compared the charge structures inferred from electric field soundings in the storms with charges inferred from three-dimensional lightning mapping data. Charge structures were inferred from electric field profiles by combining the one-dimensional approximation of Gauss's law with additional information from three-dimensional patterns in the electric field vectors. The three different ways of inferring the charge structure in the storms were found to complement each other and to be consistent overall. Charge deposition by lightning possibly occurred and increased the charge complexity of one of the storms.Many of the cloud flashes in each case were inverted-polarity flashes. Two storms produced ground flash activity comprised predominantly of positive ground flashes. One storm, which was an isolated thunderstorm, produced inverted-polarity cloud flashes, but no flashes to ground. The positive and negative thunderstorm charge regions were found at altitudes where, respectively, negative and positive charge would be found in normal-polarity storms. Thus, we conclude that these storms had anomalous and inverted-polarity electrical structures. Collectively, these three cases (along with the limited cases in the refereed literature) provide additional evidence that thunderstorms can have inverted-polarity electrical structures.  相似文献   

各向异性半空间上方垂直磁偶极子电磁场的球面波展开式   总被引：3，自引：0，他引：3       下载免费PDF全文

江滨浩  刘永坦 《地球物理学报》2005,48(5):1191-1196

文中推导出单轴各向异性媒质半空间上方垂直磁偶极源电磁场的精确解析表达式. 应用圆柱波函数的球面波展开式和超几何函数理论，场分量中的索末菲尔德型积分被表示成快速、绝对收敛的球面波函数系展开式；展开系数是以物性参数为复宗量的勒让德多项式. 该展开式数学物理意义明显，并且不受场点和源点的位置、媒质的物性参数和频率等条件的限制. 利用本文的结果可十分方便地计算和分析任意场点处的电磁场分布.  相似文献   

Lithologic control of debris torrent occurrence   总被引：1，自引：0，他引：1  

Shannon Sterling  Olav Slaymaker 《Geomorphology》2007,86(3-4):307-319

A field-based investigation into the frequency and magnitude of debris torrent systems reveals that lithology controls the spatial and temporal occurrence of debris torrents in the Tsitika Watershed, Vancouver Island, British Columbia. We identified 125 debris torrent systems in the watershed; for half these basins we used dendrochronology, historical air photographs, and field surveys to estimate debris torrent frequency and magnitude for a 30 year period. We find that the volcaniclastic half of the watershed contains more than twice as many debris torrent systems, in which debris torrents occur over seven times more frequently, and the deposits have a higher rate of delivery of sediment to the mainstem river than the intrusive half. Lithologic differences in weathering rates, weathering product grain size, and rock texture can explain the observed differences in debris torrent behaviour. Because debris torrents are the main sediment transport path from hilltop to valley bottom in the region, these results confirm an important lithologic control on regional sediment transport. While the exact numbers are uncertain, we estimate that the sediment flux of volcaniclastic debris torrents in the watershed is five times higher than that of the intrusive debris torrents.  相似文献   

Application and verification of fuzzy algebraic operators to landslide susceptibility mapping   总被引：4，自引：2，他引：4  

Saro Lee 《Environmental Geology》2007,52(4):615-623

The aim of this study was to apply and to verify the use of fuzzy logic to landslide susceptibility mapping in the Gangneung area, Korea, using a geographic information system (GIS). For this aim, in the study, a data-derived model (frequency ratio) and a knowledge-derived model (fuzzy operator) were combined. Landslide locations were identified by changing the detection technique of KOMPSAT-1 images and checked by field studies. For landslide susceptibility mapping, maps of the topography, lineaments, soil, forest, and land cover were extracted from the spatial data sets, and the eight factors influencing landslide occurrence were obtained from the database. Using the factors and the identified landslide, the fuzzy membership values were calculated. Then fuzzy algebraic operators were applied to the fuzzy membership values for landslide susceptibility mapping. Finally, the produced map was verified by comparing with existing landslide locations for calculating prediction accuracy. Among the fuzzy operators, in the case in which the gamma operator (λ = 0.975) showed the best accuracy (84.68%) while the case in which the fuzzy or operator was applied showed the worst accuracy (66.50%).  相似文献