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四川小金抚边河断裂的晚第四纪活动特征 总被引：6，自引：0，他引：6
１９８９年９月２日小金６．６级地震和本次地震的前震（１９８９年３月１日的５．０级）及余震（１９９１年２月１８日的５．０级）均发生于小金两河口－木城附近,这３次地震的震中连线及其等烈度线长轴皆大致呈Ｎ３０°Ｗ方向,暗示着该区存在北西向的活动构造。本在航空照片判译和野外实地调查的基础上,初步查明了抚边河断裂的空间展布特征,通过断错地貌的研究,结合热释光（ＴＬ）的测龄结果,首次发现了抚边河断裂晚第四纪 相似文献
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四川较场弧形构造与1933年叠溪地震发震构造的再讨论 总被引：5，自引：0，他引：5
较场弧形构造是四川众多弧形构造带之一。本文对该弧形构造的特征及其西冀发育的松平沟断裂的新活动性作了进一步论证，确认松平沟断裂属全新世活动断裂。该弧形构造西翼弧顶部位1933年曾发生过叠溪7．5级地城,丧人对该次地震的发震构造众说纷纭。作者通过近年来在现场的多次考察，并对该次地震的等烈度线形态，地表震害展布特征，建筑物沿松平沟断裂的左旋位错，震后持表发育的西北向地震地裂缝等现象的进一步研究认为，1933年叠溪7．5级地震的发展震构造仍为较场弧形构造西翼的松平沟断裂。 相似文献
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成都平原最大可能地震能力估计 总被引：4，自引：1，他引：4
成都平原位于青藏高原的东南缘，紧靠龙门山推覆构造带。近代地壳运动，断裂活动和地震活动水平应介于青藏高原活动构造区和四川盆地弱活动构造区的过渡地带。本文从构造类比角度对成都平原的最大可能地震能力进行了评估；结果表明其最大可能地震能力高于该区的地震史载水平。其中，蒲江－新津－成都德阳断裂可达６±０．５级，大邑－彭县－绵竹隐伏断裂可达５．６级左右。 相似文献
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兰州地区活动构造的基本特征 总被引：5，自引：0，他引：5
兰州地区发育了NWW向和NWW向2组主导性活动构造带。大致以河口为界，东部地区主要为NWW向的马衔山－兴隆山左旋逆走滑活动断裂系，其新活动明显，是区内的主要控震断裂，1125年兰州7级地震就发生在其中的马衔山北缘断裂带的西端。河口以西为拉脊山北缘断裂和庄浪河断裂等1组NWW向的弧形逆冲断褶带，变形方式以断裂扩展褶皱为主，其新活动可能导致了138年金城－陇西63／4级地震、1440年永登61／4级地震和1995年永登5.8级地震的发生。兰州市区所在的兰州盆地则夹持在上述2组活动构造之间，其内同样发育了NWW向和NWW向的次级断裂，如刘家堡断裂、金城关断裂、雷坛河断裂及深沟桥断裂等，其上具有孕育和发生中强震的构造条件。 相似文献
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对 138年金城 -陇西 6 3/4 级地震的历史资料考证、黄土滑坡分布及活动构造的综合研究表明 :在 138年地震中遭破坏的东汉金城郡郡治允吾县应在今青海省民和县马场垣乡下川口附近 ;陇西郡治狄道县在今甘肃省临洮县城。由此确定 138年地震的极震区位置大致在今甘肃省永靖县西北的湟水、黄河交汇地带。该区也是黄土滑坡密集分布区 ,其中的大型滑坡应为地震滑坡。在构造上该区位于拉脊山北缘弧形逆冲断裂带的前缘。拉脊山北缘断裂带为一条晚更新世活动断裂 ,部分地段为全新世活动 ,其向NE方向的逆冲推覆致使古近系泥岩和早更新世砾岩等发生了明显的挤压褶皱变形。石油勘探资料也证实拉脊山北缘弧形构造带前缘在深部存在隐伏的挤压逆冲断褶带。由此推断 138年金城 -陇西 6 3/4 级地震的发生很可能与该逆断裂 -褶皱带的新活动有关 相似文献
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1739年平罗8级地震发震构造 总被引：4，自引：0，他引：4
《地震地质》2015,(2)
1739年平罗8级地震是银川平原上有史以来发生的最大一次破坏性地震。关于该地震的发震构造尚有不同认识。在近年获得的探槽、钻探、浅层地震勘探等资料的基础上,对红果子长城及周边台地的地震位错现象开展了调查和详细测量,并再次探讨了1739年平罗8级地震的发震构造。结果表明,贺兰山东麓断裂的最后一次破裂事件发生在距今600~700a之后,修筑于500a前的明长城被错断。尽管银川隐伏断裂的展布和极震区相吻合,但该断裂向北终止于姚伏镇,全新世活动段长度不超过36km,其最后一次地表破裂事件发生在距今3 400a之前不久,银川隐伏断裂在1739年平罗8级地震中没有发生地表破裂。断裂附近生长地层的发育和地层无同步变形的事实表明,银川隐伏断裂并没有发生被松散层吸收而未抵达地表的破裂。因此,1739年8级地震的发震构造是贺兰山东麓断裂而非银川隐伏断裂,2条断裂没有发生同步牵连活动。平罗8级地震的发震构造和极震区分布的异位,可能与断裂倾向、地下水位深度、盆地结构、松散地层厚度、居民聚集等因素有关,这类由盆地边界铲形断裂发震而极震区向盆地中心偏移的现象,应在类似地区的抗震设防中予以重视。 相似文献
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南黄海6.1级地震构造背景分析 总被引：9，自引：2，他引：7
在分析了地质构造、地球物理场，地震活动性，地震烈度和地壳应力场等资料的基础上，认为长江口外的崇明东凹陷及其相关的北东，北西向隐伏断裂，对１９９６年南黄海６．１级地震的发生可能具有一定的控制作用。 相似文献
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安徽巢湖—铜陵地区是中国大陆内部1个典型的中强地震活动区,曾发生的1585年巢县南5级、1654年庐江东南5级等4次地震呈NNE向带状展布,构成了1条醒目的中强地震活动带。野外地表地质调查、浅层物探、钻探资料、年代学样品的采集测试和断裂活动性综合分析等表明该地区矾山断裂、夏家岭断裂和朗村断裂是前第四纪断裂。铜陵断裂是1条中更新世活动的隐伏断裂,可发生中强地震,控制了近地表的3个雁列状构造的演化和发展。4次地震强度呈现了向S递减的特点,而这与晚新生代无为盆地的凹陷幅度明显大于南边的贵池盆地的特点相一致。在深部构造上,铜陵断裂空间分布特征对应着1条NNE向布格重力异常梯级带。巢湖—铜陵地区中更新世活动的铜陵断裂、雁列状分布的构造、新构造的差异运动以及布格重力异常梯级带与该地区中强地震活动带在空间上的对应性,显示了它们应是中强地震孕育和发生的构造标志。 相似文献
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D. M. Pechersky A. A. Lyubushin Z. V. Sharonova 《Izvestiya Physics of the Solid Earth》2010,46(7):613-623
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. 相似文献
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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. 相似文献
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Prof. Dr. W. A. Heiskanen 《Pure and Applied Geophysics》1958,41(1):1-18
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. 相似文献
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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。 相似文献
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V. E. Pavlov T. Yu. Tolmacheva R. V. Veselovskiy A. V. Latyshev A. M. Fetisova I. V. Bigun 《Izvestiya Physics of the Solid Earth》2017,53(5):702-713
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. 相似文献
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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. 相似文献
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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. 相似文献
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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... 相似文献