Spherical cap harmonic analysis: a comment on its proper use for local gravity field representation

Spherical cap harmonic analysis is the appropriate analytical technique for modelling Laplacian potential and the corresponding field components over a spherical cap. This paper describes the use of this method by means of a least-squares approach for local gravity field representation. Formulations for the geoid undulation and the components ξ, η of the deflection of the vertical are derived, together with some warnings in the application of the technique. Although most of the formulations have been given by another paper, these were confusing or even incorrect, mainly because of an improper application of the spherical cap harmonic analysis. Received: 16 January 1996 / Accepted: 17 March 1997     

我院近景摄影测量的回顾与展望

本文在全面阐述我院十多年来开展近景摄影测量应用研究和主要成果的基础上，提出了今后主要工作内容和发展方向。     

应用气象卫星NOAA-AVHRR图像进行植被研究的多时相途径

本文讨论了应用NOAA-AVHRR数字图像研究植被季相变化和进行植被分类的多时相方法。对生长季节的各时相植被指数VI图像进行图像分割,可揭示植被绿锋的进退和季相变化及其在空间上的表现。对多时相的植被指数VI图像进行主成分变换,据第一主成分的直方图各特征峰的形状和位置进行图像分割,可获得植被景观图,这一结果与现行的植被分布图相当一致。     

地震波的计算机自动提取——智能跟踪与细化

本文通过对地震图特征的分析,提出了一个地震波的计算机自动提取方法.该方法由地震图扫描输入、灰度规一化、水平线消除、时标和起震点提取及智能跟踪与细化等步骤组成.在地震波的跟踪与细化过程中,充分利用了地震波的先验知识,以提高地震波自动提取的智能化水平.实验证明,该方法可取得较满意的结果.     

From granulites to eclogites in the Sesia zone (Italian Western Alps): a record of the opening and closure of the Piedmont ocean

The Sesia zone (Italian Western Alps) offers one of the best preserved examples of pre-Alpine basement reactivated, under eclogite facies conditions, during the Alpine orogenesis. A detailed mineralogical study of eclogitized acid and basic granulites, and related amphibolites, is presented. In these rare weak to undeformed rocks microstructural investigations allow three main metamorphic stages to be distinguished.
(a) A medium- to low- P granulite stage giving rise to the development of orthopyroxene + garnet + plagioclase + brown amphibole + ilmenite ± biotite in basic granulites and garnet + K-feldspar + plagioclase + cordierite + sillimanite + biotite + ilmenite in acid granulites.
(b) A post-granulite re-equilibration, associated with the development of shear zones, producing discrete amphibolitization of the basic granulites and widespread development of biotite + sillimanite + cordierite + spinel in the acid rocks.
(c) An eo-Alpine eclogite stage giving rise to the crystallization of high- P and low- T assemblages.
In an effort to quantify this evolution, independent well-calibrated thermobarometers were applied to basic and acid rocks. For the granulite event, P-T estimates are 7–9 kbar and 700–800° C, and for subsequent retrograde evolution, P-T was 4–5 kbar and 600° C. For the eo-Alpine eclogite metamorphism, pressure and temperature conditions were 14–16 kbar and 550° C.
The inferred P-T path is consistent with an uplift of continental crust produced by crustal thinning prior to the subduction of the continental rocks. In the light of the available geochronological constraints we propose to relate the pre-Alpine granulite and post-granulite retrograde evolution to the Permo-Jurassic extensional regime. The complex granulite-eclogite transition is thus regarded as a record of the opening and of the closure of the Piedmont ocean.     

Synthetic isoseismals of three earthquakes in California and Nevada

Recent tests on a series of earthquakes in California and Nevada suggest that in some regions the approximate shapes of the territories with equal earthquake-induced damage (expressed in terms of macroseismic intensity) could be synthetically traced out with a simple formula. This formula takes into account some gross features of the source: depth and length, unilateral or bilateral rupture, radiation patterns, rupture velocity, and directivity. Having been formulated on an empirical basis, the formula is however compatible with the so-called asymptotic approach, in which the far-field component of the Green's function is used. This paper presents the synthetic isoseismals of the earthquakes at Cedar Mountain, Nevada, 1932; Fairview Peak-Dixie Valley, Nevada, 1954; and Coalinga, California, 1983. An overall consistency, from acceptable to remarkable, between the observed intensity patterns and the synthetically back-predicted intensity has been obtained for them. Where the detailed modelling techniques available today are inapplicable, due to insufficient information on the features of the seismic sources, or to save time and money, the new formula may be utilizable for improving seismic hazard calculations.The formula was also used inversely for back-predicting geometric-kinematic parameters of the Coalinga 1983 earthquake from macroseismic maps. This gave characteristics for its source which are in good agreement with the majority of data inferred from modelling and from analyzing modern instrumental recordings. This striking result opens new perspectives in retrieving information on the source of ancient earthquakes for which only macroseismic information is available.     

The New Seismic Zonation Map for the Territory of Armenia

In the present work a new, deterministic, seismic zonation map for the territory of Armenia is presented. It has been compiled on the basis of the newest seismological, geological and geophisical data. Creation of the map included: determination of a seismic hazard area for the territory of Armenia; compilation of a map of active faults; identification of active blocks; identification of seismic source zones; calculation of a seismic effect from the seismic source zones (SSZs). Seismic effect on the Earth's surface from the singled out SSZs is calculated in the form of an intensity of seismic influences expressed in units of MSK-64 scale, and horizontal soil accelerations expressed in fractions of gravity force acceleration (g). The map compiled will allow comparison between the deterministic model with a probabilistic seismic zonation model for the territory of Armenia (in preparation), in order to analyze the western and eastern standards of seismic hazard assessment on the basis of the same complete data base.     

内蒙古河套地方性砷中毒区地质环境特征与成因探讨

论文通过对内蒙古砷中毒病区地质环境调查和防砷改水试验工作。从病区地质环境特征入手，系统分析了构造环境；第四纪地质环境水文地质环境，水化学环境，岩矿地球化学环境和古地理及生物化学环境等诸方面特征，对高砷的地质环境成因进行了探讨．得出十条高砷病区与地质环境之间的成因关系，认为高砷病区的形成与地质环境特征有着密切的成因联系．地方性砷中毒是在特定的地质环境条件下形成的。这对地方性砷中毒的形成、分布及防治具有一定的指导意义，亦为后期防砷改水提供了科学依据。     

利用相对波阻抗识别煤层缺失变薄带

地震道积分是利用地震资料进行的无约束反演技术,也就是通过对地震道积分得到地层的相对速度剖面而进行地层分析的技术。通过地震道积分识别煤层缺失变薄带研究表明,小规模的煤层缺失变薄带在三维地震时间剖面上基本无显示,在地震道积分时间剖面上能够有效地识别出相对波阻抗的异常,进而解释煤层缺失变薄带,解释成果与巷道揭露一致,结果表明地震道积分是地震解释中一项的有效实用技术。