震兆平静的再认识--海城地震30周年有感于经验性地震预报的议论

从对海城地震时期所关注的平静震兆的再认识中,阐明了经验性地震预报在探索地震预报从无到有的历程中所能发挥的作用。     

浅析地震科学对社会发展的影响

随着社会及学科的发展,越来越多的地震知识应用于社会领域,对社会的发展具有极大的促进作用,为此有必要进一步探讨地震科学的影响。从地震预报、工程地震、震害预测、震灾评估、地震宣传和地震速报与应急等方面讨论了地震科学对社会发展的影响。结果表明,地震科学具有重要手社会价值和广泛的应用前景。在此基础上,提出应进一步加强地震震源、地球内部结构和地震预报等学科的研究,并展望了共应用前景。     

关于加强地震预报基础研究的思考

回顾了国内外地震预报研究40年的经历和现状，指出几十年来所取得的科学进展与突破地震预报的科学目标之间还有相当的距离。文章分析了地震预测中的科学难点，提出了加强地震预测基础研究的重要性和必要性，并指出了加强地震预报基础研究的若干科学问题。     

地震预报的现状与前景

对当前我国的地震监测手段和预报能力作了分析了估计，认为对地震预报现状看法的分岐，实质上是对地震预报发展战略的争论，指出当前地震预报所面临的困难；加强前兆机理的地震孕育过程研究，缩短战线重点攻关是推进地震预报事业的有效途径。     

我国地震预报研究概述

文章全面介绍了１９６６￣１９９６年我国地震预报研究历程及所获得的主要成果，针对我国大陆地震活动频率高，强度大，分布范围广，震源浅、地震灾害严重的特点，以大陆板内地震活动规律和前兆观测研究为主要目标的我国地震预报研究，着重从我国地震及前兆观测台网建设和研究，中长期地震预测研究和地震重点监测防御区确定以及中短期地震预报研究三方面进行了艰苦的探探索，但由于板内地震活动及前兆现象极其复杂，多样，我国中长期     

关于短临地震预报的几点看法

我仅就短临地震预报简谈以下观点。1　短临地震预报存在的问题如果短临预报的科学含义是 :1月际地震趋势预测 ;2月际内地震事件发生的预测 ;3月际地震趋势和地震事件的社会发布。那么 ,我国短临地震预报就存在有不少基本性的科学技术问题。试以事实为例简析之。1 .1　趋势问题图 1是我国国家级分析预报业务系统对2 0 0 0年 1月至 2 0 0 1年 1月期间所作出的短临地震预测趋势标识曲线和实际地震趋势演变曲线。从比较中不难看出 :1差异显著 ,客观趋势的高低走向变化 ,主观预测毫无能力显示 ;2预报者们需要研究科学预报原理 ,避免“猜报”;3预…     

地震概率预报效能评分和预报发布决策

我国地震预报的发展已经到了这样的阶段:我们不但面临地震预报问题,而且面临如何应用决策理论科学地向公众发布短临预报的问题。为此,除了目前已经开展的地震易损性研究外,还要研究预报向公众发布后引起的社会经济效应及采取预防措施所需的经济代价;此外,还应实现从确定性地震预报向概率地震预报的转变。概率预报是地震活动本身特点所要求的科学的预报方法,它可以使我们把长期地震危险性分析和短临预报有机的结合起来,进行定量的决策分析,更科学的决策是否和如何向公众发表地震短临预报,取得更好的社会效益。为了在短临预报中推广概率预报,必须正确理解概率预报的含义和对概率预报效能进行评价。     

1998年1月10日张北-尚义6.2级地震前的区域地震活动异常和预报

1998年1月10日张北-尚义发生了6.2级地震,这次地震前区域地震活动显示出了明显的异常特征,中期预报效果比较成功,对于这次地震没有作出短临预报,这既有地震孕育过程的复杂性和地震预报的高难度问题,也存在一定程度的预报技术思路问题。近几年来作者对在北京西北的晋、冀、内蒙古交界地区形成的以地震活动条带为代表的多项地震活动异常给予关注,现反思张北-尚义6．2级地震之前的某些前兆异常现象和预报过程,对于今后的地震预报研究具有借鉴的意义。     

论地震预报策略

在当今地震预报科学水平还很低,而社会又强烈地期望实现地震预报的情况下,地震社会学问题更显突出。地震预报策略,就是管理部门在充分尊重地震预报专家地震预测预报意见的基础上,以何种形式和口径向上级领导机关报告或向社会公众通报的策略,以取得防御和减轻地震灾害的最佳效果。论述了目前使用的９种地震预报策略的要点及正负效应。     

地震社会学与地震预报

人们对地震危险度感觉的三要素是；可预报的地震的摧毁程度，预报意见的准确度以及所预报的地震来临的迫切程度。这三要素既是地震预报问题，同时也是在地震社会学问题密切相关的。今后要研究多种严重不利因素与地震问题重合下的地震社会学问题。     

On the synchronism in the events within the core and on the surface of the earth: the changes in the organic world and in the polarity of the geomagnetic field in the phanerozoic

The data on geomagnetic reversals are compared with the changes in the organic world and with the lower-mantle plumes. The times of the formation of plumes and the times of their appearance on the Earth’s surface relate to the intervals characterized by the different frequencies of geomagnetic reversals, i.e., there is no interrelation between the formation of plumes and the frequency of the changes in the geomagnetic field polarity. At the same time, a certain synchronism is observed between the frequency of the geomagnetic reversals and the boundaries of the biostratigraphic ages, i.e., the changes in the organic world in the long-period range. A hypothesis is proposed, which explains the change in the sign of the geomagnetic field by the combined effect of the irregular rotation of the internal core relative to the mantle and the changes in the slope angle of the axis of the Earth’s rotation, which, in turn, results in synchronous events on the Earth’s surface: the rates of changes in the organic world.     

On the maintenance of the axisymmetric part of the flow in the atmosphere

Summary The maintenance of the axisymmetric component of the flow in the atmosphere is investigated by means of a steady-state, quasi-geostrophic formulation of the meteorological equations. It is shown that the meridional variations in the time-averaged axisymmetric variables can be expressed as the sum of three contributions, one being due to the eddy heat transport, another to the eddy momentum transport, and a third to the convective-radiative equilibrium temperature which enters the problem through the specification of a Newtonian form of diabatic heating. The contributions by the large scale eddies are evaluated through the use of observed values for the eddy heat and momentum transports.The contributions from each of the three forcing mechanisms to the temperature and zonal wind fields are invstigated individually and found to be of about equal importance. The sum of the three contributions are also presented for the temperature, the zonal wind, the stream function associated with the mean meridional circulation and the corresponding vertical motion. Although the results fail to reproduce the main observed features of the lower stratosphere, they are found to be in good agreement with observations in the middle latitude troposphere. At any pressure level, for example, the computed mean zonal wind has a jet-like profile and the axis of the jet is found to slope to the south with height, as observed in the atmosphere.Based in part on a thesis submitted by the first author as partial fulfillment of the requirements for the Ph.D. degree at the University of Michigan. — Publication No. 194 from the Department of Meteorology and Oceanography, The University of Michigan.     

On the gravimetric undulations of the geoid and the deflections of the vertical

Summary The author mentions the aims of the World-wide gravity project he established in the Ohio State University in Columbus, in 1950. He outlines the practical procedure of the gravimetric computations of the undulationsN and the vertical deflection components and and emphasizes that only by the global international cooperation and additional gravity observations at sea carried out during the last decade it has been possible to gather to Columbus the needed gravity material. Since there exist still large gravimetrically unsurveyed areas it is of vital significance to study what gravity anomalies are best to be used for these regions. The given figures concerning the accuracy of theN, and , estimated theoretically and obtained in practice, indicate that in the gravimetrically well surveyed parts of the world like in Europe and the United States we can get gravimetrically on basis of existing gravity material theN-values with accuracy of about 5–10 meters, and and with the accuracy of about 1. The geoid undulationsN are already computed in Columbus for more than 6000 points of the northern hemisphere. The sample maps show the interesting geoid of Europe and vicinity between the latitudes 60° and 30° and longitude 5° W and 30° E, drafted on basis of more than 1000N-values computed at the corners of 1°×1° squares. It is interesting to realize that the geoid undulations in all this area are positive, the extreme values being between 40 and 50 meters. The geophysical significance of the geoid maps of this kind is pointed out.     

太平洋中部地磁台11年周期变化的研究

综合APIA、HONOLULU、PAMATAI 3个地磁台三分量的11年周期变化的形态后,可定性地提出该变化源于内场。如内源为核幔边界的电涡流,则其中心点应位于3台之间。     

Magnetic stratigraphy of the Ordovician in the lower reach of the Kotuy River: the age of the Bysy-Yuryakh stratum and the rate of geomagnetic reversals on the eve of the superchron

Until recently, the existing data prevented the geophysicists from accurately dating the Bysy-Yuryakh stratum, which outcrops in the middle reach of the Kotuy River, constraining the time of its formation to a wide interval from the end of the Late Cambrian to the beginning of the Silurian. The obtained paleomagnetic data unambiguously correlate the Bysy-Yuryakh stratum to the Nyaian regional stage and constrain its formation, at least a considerable part of it, by the Tremadocian. This result perfectly agrees with the data on the Bysy-Yuryakh conodonts studied in this work and yields a spectacular example of the successful application of paleomagnetic studies in solving important tasks of stratigraphy and, correspondingly, petroleum geology. Within the Bysy-Yuryakh stratum, we revealed a large normal-polarity interval corresponding to the long (>1 Ma) period when the geomagnetic reversals were absent. This result, in combination with the data for the Tremadocian and Middle–Upper Cambrian sequences of the other regions, indicates that (1) the rate of occurrence of the geomagnetic reversals on the eve of the Ordovician Moyero superchron of reversed polarity was at most one reversal per Ma; (2) the superchron does not switch on instantaneously but is preceded by a certain gradual change in the operation conditions of the dynamo mechanism which, inter alia, manifests itself by the reduction of the frequency of geomagnetic reversals with the approach of the superchron. This finding supports the views according to which a process preparing the establishment of the superchrons takes place at the core–mantle boundary.     

On the variation in the geomagnetic dipole over the geological history of the Earth

The global database on the paleointensity, containing determinations of the virtual dipole moment (VDM) for a stable (normal) regime of the geomagnetic field in a time interval of up to 3.5 Ga, is supplemented by new VDM determinations and analyzed. The field generation process started no later than 3–3.5 Ga (earlier data are absent) at the stage of the Earth’s core formation. Since that time, the dipole value has differed from its present value by no more than an order of magnitude, and the deviations that have already been detected tend toward smaller values. The distribution of VDM values in the time interval 0–400 Ma is bimodal, which apparently reflects the presence of two different generation levels of the geomagnetic field distinguished by a relatively large value (close to the present field value) and a relatively small value (approximately half as large as the present value). The total duration of decreased VDM values appreciably exceeds that of increased VDM values (179.1 and 28.6 Myr, respectively). On the whole, data on the paleointensity do not contradict the hypothesis about the dipole nature of the field over the last 400 Myr; however, the number of determinations at high paleolatitudes is too small to draw decisive conclusions on the validity (or invalidity) of the dipole field approximation based solely on paleointensity data.     

Comparison Between the Nutations of the Planet Mars and the Nutations of the Earth

The nutations of the planets Mars andEarth are investigated and compared. Alarge number of interior structureparameters are involved in the nutationcomputations. The comparison between the observations and the computationsprovides several constraints on these parmeters andtherefore allows a better understanding of the physics of the interior of theplanet. For the Earth, the high precision of the observations of the nutationshas led to a very good determination of interior properties of the planet. ForMars, observations of nutations are not yet available, and we review how theamplitude of the Martian nutations depends on the hypotheses consideredfor its interior. Although Mars is very similar to the Earth, its interior is not well known;for example, we don't knowif its core is liquid or solid. Only if the core is liquid,the Free Core Nutation (FCN) normal mode exists and can alter the nutationswhich are close to the resonance. From the observed geoids, it is known thatboth planets are not in hydrostatic equilibrium. The departure is larger forMars than for the Earth, and consequently, the implication of considering a convective mantle instead of a mantle in hydrostatic equilibrium described byClairaut's equation for the initial equilibrium state of the planet is largeron the Martian nutations than on the Earth nutations. The consequences of theuncertainty in the core dimensions are also examined and shown to be of a veryhigh influence for Mars if the core is liquid, due to the potential changes inthe FCN resonance. The influence of the presence of an inner core, which isknown to exist for the Earth, could be more important for Mars than for theEarth if the inner core is large. Due to the presence of Tharsis on Mars, thetriaxiality of this planet has, additionally, larger effects than on Earth.     

Evolutionary Changes in the Configuration of the Magnetic Field of the Solar Corona in the Epoch of the Minimum

Geomagnetism and Aeronomy - The evolution of the magnetic configuration in the solar corona is studied. The curvature of the K-corona helmets obtained from an analytical approximation of the...