The establishment of GPS network in Grove Mountains, East Antarctica

1 Introduction The Grove Mountains is located at Princess Elizabeth land in East Antarctica, about 400 km from Zhongshan station and 160 km east of the Mawson Escarpment, consists of a scattered group of mountains and nunataks. The range extends73°-76°E…     

Geodetic deformation vs. seismic strain deduced by historical earthquakes across the Alborz Mountains

Historical seismicity is used in order to map spatial distribution of seismic moment released by past earthquakes and to compare strain rate deduced from seismicity to those measured by geodetic GPS survey. Spatial analyses are performed on the seismicity of northern boundary of Central Iranian Block which coincides with the Alborz Mountains. This belt has been responsible for several catastrophic earthquakes in the past. In this study, the records of historical and instrumental earthquakes in the Alborz Mountains are used to calculate and plot geographical distribution of seismic moment released in time. A two-dimensional distribution function is proposed and used here to spread seismic moment along causative tectonic features. Using accumulated seismic moment, average slip rates across active faults are estimated for 32 sub-zones along the Alborz Mountains and western Kopet Dag. Seismic moment released by historical and recent earthquakes on this belt accounts for slip rate of 3–5 mm/year which is in good agreement with the geodetic vectors recently deduced from GPS survey in this region. The study also reveals geographical variations of slip rates along some 900 km length of this zone based on seismic history. The results are compared against finding from similar study in this region. Portions of Central and Eastern Alborz show lower seismic strain rate which could imply aseismic motion or overdue earthquakes. Completeness of historical earthquake catalogue and its reliability with regard to earthquake magnitudes, locations, and rupturing systems are among many plausible factors controlling the credibility of such results. Therefore, any conclusions derived from these results remain as reliable as the data and assumptions used for the analyses.     

空间大地测量技术对确定地面坐标框架、地形变与地球重力场的贡献和进展--出席2005年国际大地测量协会(IAG) 科学大会札记

国际大地测量协会（IAG）科学大会于2005年8月22~26日在澳大利亚凯尔斯（Cairns）召开。会议名称为“动力行星2005”（Dynamic Planet 2005）。会议就有关完善全球和地区性地面坐标参考框架、卫星重力测量在确定地球重力场时空分辨率、开展航空激光和雷达成像及其干涉技术在地形变和灾害监测,以及对大气的研究、建立和完善全球大地测量观测系统(GGOS)、开展行星大地测量的研究等方面的内容做了广泛的学术交流,内容比较丰富。     

On the ellipsoidal correction to the spherical Stokes solution of the gravimetric geoid

The solutions of four ellipsoidal approximations for the gravimetric geoid are reviewed: those of Molodenskii et al., Moritz, Martinec and Grafarend, and Fei and Sideris. The numerical results from synthetic tests indicate that Martinec and Grafarends solution is the most accurate, while the other three solutions contain an approximation error which is characterized by the first-degree surface spherical harmonic. Furthermore, the first 20 degrees of the geopotential harmonic series contribute approximately 90% of the ellipsoidal correction. The determination of a geoid model from the generalized Stokes scheme can accurately account for the ellipsoidal effect to overcome the first-degree surface spherical harmonic error regardless of the solution used.     

应用GPS技术对龙羊峡水库库岸滑坡监测的可行性分析

近20多年来,由于空间技术的飞速发展,从宇宙空间测量地球的方法越来越多地引起人们的关注.特别是近几十年以来的GPS技术引入测量学,使经典的测量技术很难解决的一些地球动力学测试问题成为现实.应用GPS技术,作者通过对龙羊峡水库库岸滑坡监测点的测试,用一系列实测数据,说明GPS技术具有较高的精度,完全能适用于对滑坡的监测.     

大气对极移的非季节性激发贡献

本文对由高精度的极移资（Ｓｐａｃｅ９３序列）所推导出的测地激发函数和由日本气象局（ＪＭＡ）提供的大气激发函数中的非季节性波动进行了研究，在两个序列中都显示出较强的４０－６０天的波动．在非季节性的时间尺度上，测地激发函数相关于大气压力变化，与与的相关系数分别为０．４４和０．５８，这表明了大气角动量对极移中ｙ轴方向的非季节性变化的影响稍大于ｘ轴方向．而且，大气和测地激发函数尤其在Ｘ２方面具有较相似的时间变化谱．这些事实说明：极移的非季节振荡至少部分地由气压变化所引起，它在１４０天以下周期的极移激发中起了一定的作用．     

Direct transformation from geocentric coordinates to geodetic coordinates

 The transformation from geocentric coordinates to geodetic coordinates is usually carried out by iteration. A closed-form algebraic method is proposed, valid at any point on the globe and in space, including the poles, regardless of the value of the ellipsoid's eccentricity. Received: 14 August 2000 / Accepted: 26 June 2002     

Predictions and observations of convergence in shallow tunnels: case histories in Greece

Convergence of shallow tunnels (30–120 m overburden thickness) constructed in Greece in different types of rock masses has been assessed as a function of the Geological Strength Index (GSI classification). Predictions of maximum vertical and horizontal convergence, during or shortly after tunnel excavation, were made using Finite Element Modeling (FEM) and the ‘characteristic line’ theory, and were found to be in good agreement with geodetic observations of convergence collected during a period of approximately 2 months after the section excavation. The results from FEM were found to adequately and reliably predict the expected deformation during tunnel excavation. The theory of the ‘characteristic line’, on the other hand, seems to offer a realistic and reliable upper-bound estimate of the convergence.     

京、津、唐地区活动断裂带的形变特征

本文主要利用复测水准、基线资料研究本区活动断裂的现代活动性。计算出近20条断裂的垂直运动量及少数断裂的水平运动量。根据断裂活动垂直运动年速率的水平将该区断裂分为两类,第一类1—10毫米,第二类小于1毫米。结合地震、地质资料讨论了本区活动断裂的现代活动特征     

我国大地重力学和固体潮研究进展

地球重力学是研究重力场时空分布及其物理机制的一门学科．地球重力场的空间分布通常可用于三个方面：一是空间科学和大地测量学，主要是利用地表的重力观测对在其上测得的几何量加以归算，以及给出重力场的高空赋值以修正卫星和近地飞行器的轨道；二是反演地球内部结构，主要是三维密度的不均匀分布，并对诸如地慢对流等作约束；三是勘探在时间变化方面，最主要影响来自固体潮，当然还有许多内部力源导致动力学效应．本文着重对我国大地重力研究和固体潮研究的进展作一回顾．