南极菲尔德斯地区重力观测研究

本文介绍了用拉柯斯特-隆贝格G型重力仪进行的南极长城站((?)=62°12′.9S,(?)=58°57′.8W)重力基准点国际联测和南极菲尔德斯地区重力及形变监测网建设和观测情况.测得长城站重力基准点重力值及精度为:982208.682±0.021mgal.极地重力网由18个重力点组成,其控制面积近40平方公里,用闭合环式方法观测.网的平均测段精度为±0.029mgal,并对不同运输情况下的观测结果进行了精度分析.     

辽宁大地构造单元重磁场特征及几个有关问题的讨论

辽宁大地构造单元的地球物理场具有多样性和复杂性。笔者根据辽宁大地构造演化和全域重、磁资料将辽宁地区台划分为5个二级构造单元,即辽东台隆、下辽河断陷带、北镇—山海关台隆、燕山台褶带和内蒙地轴。其中北镇—山海关台隆是根据重、磁场特征新确立的二级构造单元。同时,重新确定了下辽河断陷带的范围,讨论了郯庐断裂带的北延走向。资料表明,下辽河断陷带(包括辽东湾、渤海海域)是在郯庐断裂带的基础上发育而成的大陆裂谷系。     

利用水平截面法对任意形状三度体的重力异常的快速正演

自然界中的地质体,不可能是规则的几何形体,用规则形体的理论方法去逼近,往往造成很大的误差。本文的方法则是对一三度体,用水平截面法对其切割,并用一多边形去逼近,从而得到一精确的数学解析表达式,来确定一三度体的重力异常。本文的方法不仅精度高,而且速度快,是目前一种比较好的正演方法。     

TM 假彩色合成卫片在土地详查中的应用

文内涉及的 TM 假彩色三波段合成卫片的波长分别为,TM2 0.53—0.61μm,TM3 0.63—0.69μm,TM4 0.78—0.90μm。根据波谱规律卫片能直观地反映区内各地理要素的空间结构及区域分布规律。作者在玉树地区的土地调查中,利用各地类图斑的影像色调特征,建立了解译标志,结合地形图能较好地确定各地类的准确界线,显示清晰的图面结构。     

Secular perturbations of fictitious satellites of uranus

Secular perturbations of fictitious satellites that are initially circular and in the equatorial plane of Uranus are discussed. Satellites located in the region where the solar perturbation is dominant become highly eccentric and inclined with respect to the equator, and have a possibility to collide with Uranus. Satellites located in the region where the oblateness perturbation is dominant keep the original eccentricity and the inclination. A scenario of a possible extinction of outer satellites of Uranus is also discussed.     

Gravity-field improvement in the Mediterranean Sea by estimating the bottom topography using collocation

The contribution of bathymetry to the prediction of quantities related to the gravity field (e.g., gravity anomalies, geoid heights) is discussed in an extended test area of the central Mediterranean Sea. Sea gravity anomalies and a priori statistical characteristics of depths are used in a least-squares collocation procedure in order to produce new depths, giving a better smoothing of the gravity field when using a remove-restore procedure. The effect of the bottom topography on gravity-field modeling is studied using both the original and the new depths through a residual terrain modeling reduction. The numerical tests show a considerable smoothing of the sea gravity anomalies and the available altimeter heights when the new depth information is taken into account according to the covariance analysis performed. Moreover, geoid heights are computed by combining the sea gravity anomalies either with the original depths or with the new ones, using as a reference surface the OSU91A geopotential model. Comparing the computed geoid heights with adjusted altimeter sea-surface heights (SSHs), better results are obtained when subtracting the attraction of the new depth information. Similar results are obtained when predicting gravity anomalies from altimeter SSHs where the terrain effect on altimetry is based on the new bottom topography. Received: 10 September 1996 / Accepted: 4 August 1997     

9711号台风及伴生暴雨的卫星云图特征

711号台风是近年来影响我国的一个强度和范围最大的台风。台风登陆时,正值天文大潮期,因而引起风暴潮,使得浙江、上海、江苏等沿海海堤坝损坏严重。台风登陆后,台风中心途经5个省,致使七省一市出现暴雨,山东及辽宁两省出现区域性大暴雨天气。直接经济损失达250亿元。本文按卫星云图上显示的9711号台风云系演变特征,将9711号台风活动过程分为四个阶段,即发展加强阶段、登陆阶段、台风外围云系与北方冷锋云系合并阶段及台风云系向温带气旋云系演变阶段。最后讨论了台风暴雨的时空分布与不同阶段台风云系的关系。     

对西北太平洋海域表层密度流的初步探索

在文［９］［１０］关于西北太平洋海面动力地形研究的基础上,本文对该海域表层密度流进行了初步探索。特别是用０．５°×０．５°方区多年船测资料,对西部边界流——黑潮进行了专门研究。结果表明,该海域表面密度流模式与主要由风驱动的大洋总的环流模式基本一致。据研究结果,对文［９］给出的海面动力地形和全球海面动力地形的某些特征作出了解释。另外,还就卫星测高在确定大洋环流的局限性和若干概念性问题提出了明确的看法。     

云南孟连中缅边境Ms7.3地震前滇西实验场的重力变化

１９９５年７月１２日,在云南省西南部的孟连县以西中缅边境发生了一次Ｍｓ７．３强烈地震。震前,距震中２８０ｋｍ以远的滇西实验场重力网红河断裂以西出现了重力异常,平均变化幅值达７０×１０＾－８ｍｓ＾－１,最大变化幅值达１１４×１０＾－８ｍｓ＾－２,云南省地震工程研究所测量队重力组根据上述重力异常变化,对此次地震作了较好的中短期预测预报。     

A Practical Example of Low-Frequency Trend Removal

Three different classical methods of removing low-frequency trends are used to detrend some instrumental data, and their effect is evaluated. The examples given here highlight problems that may occur whenever detrending is necessary. The trend present in the data arises from the passage of synoptic weather systems over the Antarctic during the operation of the instrument. The resultant signal varies over a period of hours. This contrasts with the phenomenon to be studied (atmospheric gravity waves), which have periods of a few tens of minutes at most and amplitudes typically one or two orders of magnitude smaller than for synoptic systems. The trend removal procedure is relevant to many more situations than the analysis of meteorological pressure data.