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利用地震走时数据,采用联合反演方法获取了江苏地区的一维P波速度模型。与仅采用初至波走时的传统天然地震走时获取方法相比,该方法充分利用了大量存在的续至波参与反演,能有效改进中下地壳的反演能力。针对地震震相目录中常存在震相标识错误的问题,采用的自动判别筛选震相方法能最大限度提高数据走时的精度,可以对不同震相进行有效区分。与其他常用一维速度模型相比,本文反演的模型对Pg、Pn震相走时拟合效果最佳,残差最小。当所用走时数据拥有较高定位精度时,该反演方法能为研究区三维速度结构成像和地震定位提供较可靠的一维速度模型。 相似文献
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关于网外地震的定位问题--利用福建区域数字地震台网资料测定台湾地震震源位置 总被引:1,自引:2,他引:1
针对地壳内部的网外地震震源的定位问题,由震相组合成不同的方程组,利用均值寻查定位法迭代求解。在选取地球物理参数模型时,考虑了台湾地震部门定位时所用的模型和华南地区地震走时表等。利用福建数字地震台网记录到的绕射波Pn、Sn的到时资料,通过定位程序测定了134个位于台湾区域的壳内地震的震源位置。测定结果与台湾地震部门在其网址上公布的结果进行比对.平均震中位詈相差9km.震源深度相差8km. 相似文献
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通过对现有地震分析软件所配置的震相走时表文件的结构类型及优劣进行分析,将震相走时表分为4种组合结构并分析其实用性。在IASPEI91震相走时表文件结构的基础上进行修改、补充和完善,从而提出了一种安全性高、适用面广、灵活性强、能存储各种结构走时表的新型走时表文件结构。应用这种新型结构震相走时表,地震分析软件可以灵活配置不同的走时表,实现精细定位,并为数字化测震台网快速利用测震资料编制和应用高精度的区域震相走时表创造了条件,对于地球深部构造研究具有一定的促进意义。 相似文献
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本文根据中国地区地震P波和S波走时表与地壳和地幔中地震波的速度分布,计算和编制中国地区深度震相pP,sS,pS;sP的走时表以及地面反射波、转换波PP,SS,PS,SP震相的走时表。自1940年Jeffreys和Bullen计算了全球平均的走时表之后,除Herrin等人重新算过pP走时表外,对于sS,sP,pS震相走时一直没有人再行算过。提出中国地区符合实际情况的深度震相走时表,对于远震记录的分析处理,提高测定震源深度的精度,揭示在某些深度和震中距离上深度震相在中国地区的特征将有一定的价值,并与中国地区地震P波和S波走时表相匹配,使之自成一个体系。我们将进一步采用一系列最新数据处理方法计算《深度震相和地面反射波、转换波走时》的软件亦可供其他地区计算走时表的参考。 相似文献
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可靠的震相走时是地震预警技术中精确测定震源位置和发震时刻的基础,本文运用STA/LTA震相识别技术,针对单台(河北红山台)2009-2021年共计12年积累的地震记录进行叠加计算,得到了红山台记录到的区域地震各震相走时曲线。结果显示,震中距0°~50°范围内红山台共成像7种震相的走时曲线,分别为P、S、PP、SS、PcS、ScS以及R面波震相,且随着组合参数变化,叠加成像的震相种类、震中距范围、清晰度均有所不同。此外,通过绘制各震相走时曲线发现,震中距0°~15°范围内,P波、S波及R波走时曲线基本呈线性变化,震中距0°~15°范围内计算得到红山台区域地震P波传播速度为7.5 km/s左右,S波传播速度为4.2 km/s左右,R波传播速度为3.5 km/s左右,介于P波和S波之间存在一个震相的走时痕迹,波速为5.4 km/s左右。本工作对于提升红山台震中距≤1 000 km的地震预警定位精度有指导意义。 相似文献
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考虑同震位错与震后黏弹性弛豫效应,采用分层地壳介质模型,定量计算了台湾地区M_S≥7.0强震对福建地区部分M_L≥4.0地震的库仑应力影响。结果显示:台湾强震对福建M_L≥4.0地震的发生影响较小,远没有达到地震触发阈值,不具有触发作用,其主要原因是这两地区距离较远。结合台湾与福建地区M-T图,认为虽然台湾强震与福建地震不属触发关系,但可以用"同期活跃"的特征来描述。当大区域背景应力状态处于较高水平时,台湾地区M_S≥7.0强震与福建地区M_L≥4.0地震同时较为活跃。在此情况下,台湾M_S≥7.0强震与福建地区M_L≥4.0地震哪个先发生都是可能的。 相似文献
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本文利用近震、地方震的各种震相的走时方程,经过变换,取得相应的二次型目标函数。对目标函数用一维寻查法、均值寻查法求出其零值点的自变量,即求得各个方程的解;再用均值寻查法求得各个方程的共解,即得震源位置。随机地处理了自2000~2003年6月福建数字地震遥测台网记录到的本省及周边地区的205个地震,定位结果显示走时残差的平均值为0.25s。在可供比较的前提下,将159个地震数据的奇异值分解法的结果与本文的结果进行对比,前者的平均走时残差为0.72s,后者为0.25s,且后者的每一个地震的走时残差都比前者小。 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