松辽盆地西北边界部分地球物理特征

松辽盆地是我国东北地区重要的地质构造单元.为探测松辽盆地西北部边界基底分布、深部结构与构造关系,沿扎兰屯经齐齐哈尔至林甸实施了约240 km的综合地球物理的探测研究,利用重力、电法等地球物理方法对其进行了综合地球物理解释.研究结果揭示了研究区的速度结构分布、重力分布、基底起伏形态及电性结构等地球物理特征:(1)满-绥断面速度资料显示,嫩江岩石圈断裂有明显的速度分界,其东南侧的松辽盆地与大杨树坳陷具有连续统一的速度结构;(2)重力反演基底显示,松辽盆地与大杨树坳陷基底连续,具有统一的基底特征;(3)二维电性反演显示,大杨树坳陷和松辽盆地两构造电性层连在一起,低阻分布形态也是一样的.以上结果结合满-绥断面速度结构分布表明大杨树坳陷是松辽盆地西部的延续,松辽盆地西部边界应扩展到大杨树坳陷西部边界,即嫩江岩石圈断裂.     

大兴安岭与两侧盆地结合地带深部电性结构与岩石圈尺度构造关系

横跨大兴安岭与海拉尔盆地和松辽盆地结合地带的大地电磁测深剖面揭示了盆山构造的深部电性结构.剖面西起海拉尔盆地东缘,向东延伸穿过大兴安岭中部,一直到达松辽盆地西缘.本文对剖面测点的二维偏离度、构造走向等进行了计算和分析,采用非线性共轭梯度(NLCG)二维反演方法对TM模式的数据进行了反演,获得了该剖面的地壳、上地幔电性结构模型,划分出三个典型构造单元:海拉尔盆地、大兴安岭和松辽盆地.研究结果表明,海拉尔盆地东缘和松辽盆地西缘浅部都呈低阻特征,但松辽盆地西缘深部电性结构比较复杂,而大兴安岭整体呈高阻特征.海拉尔盆地东缘可能属于兴安块体,松辽盆地西缘与大兴安岭接触关系复杂.海拉尔盆地东缘岩石圈厚度约为110km,大兴安岭岩石圈厚度约为110~150km.大兴安岭上地壳基本呈高阻特征,可能为多次叠置的岩浆岩,代表大兴安岭经历了多期次岩浆作用;中下地壳横向存在较大范围低阻体,可能反映了大兴安岭地壳内部非刚性的特点;残存在岩石圈地幔的高阻异常,说明其下地壳可能发生过拆沉作用.大兴安岭与松辽盆地结合带存在一个岩石圈尺度的西倾低阻带,向下延伸到岩石圈底部,可能是早期松嫩地块向兴安地块俯冲并以软碰撞形式拼合的构造遗迹.     

黄河上游地区地热场初步分析

运用热流、地温梯度及温泉等资料,划分了黄河上游地区的地热异常区,讨论了地热与构造及地震的关系。认为断裂构造及深部热源是地热异常的主要成因;在空间上,强震分布与热异常区的分布呈相关关系。     

华北坳陷中南部深部结构大地电磁探测

为研究华北坳陷中南部河南地区的深部电性结构和该区3次破坏性地震的深部孕震背景，采用宽频带大地电磁测深法对该区深部的电性结构进行探测。使用NLCG二维反演方法对TE、TM模式进行联合反演，最终获得研究区的深部电性结构。结果显示，以新乡-商丘断裂为界，其北部的北华北坳陷中的内黄隆起、东濮凹陷的电性结构相对简单，为低阻、高阻2层结构，与该区地壳由沉积盖层和基底整体性较好的坚硬地块结晶基底组成相对应。新乡-商丘断裂以南的南华北坳陷中的构造单元深部的电性结构相对复杂，纵向上表现为低—高—低3层结构，横向上高阻、低阻交互出现，分析其可能与受到扬子板块与华北板块南缘相互俯冲碰撞影响有关。而北华北坳陷因边界断裂———新乡-商丘断裂的调控，受到扬子板块和秦岭-大别造山带造山作用的影响较小。1342年和1918年河南通许2次破坏性地震的震源位于太康隆起下方的高、低阻边界交接区域，1737年河南封丘■级地震的震源位于壳内高、低阻梯度带附近。     

佳木斯地块及东缘岩石圈电性结构特征

佳木斯地块及东缘是中国东北地区的重要地质构造单元. 为探测该地区地壳深部结构与构造关系,沿桦南—饶河实施了240 km的大地电磁测深的探测研究. 采用光滑模型二维反演方法对桦南—饶河大地电磁剖面的探测数据进行了二维反演和综合地球物理解释. 研究结果揭示了研究区断面域的电性结构：(1)剖面西段具有稳定的高阻特征且具有稳定的岩石圈厚度（约90km）,在十几公里深度范围存在壳内高导层,该区段对应佳木斯地块. (2)剖面中部具有明显的电性梯度带,该梯度带反映了佳木斯地块的东界位置及其深部的结构形态. (3)剖面东段电性特征揭示了佳木斯地块以东区段浅部为逆冲推覆体,深部为多个高阻块体和低阻条带相间的电性结构,这些高阻块体可能为早期俯冲的岩石圈残片.     

滇西南地区南汀河断裂带三维深部电性结构及其孕震环境

南汀河断裂带为滇西南地区活动断裂体系中规模最大的一条北东向断裂,其构造活动及地震危险性一直备受关注.本文基于覆盖云南境内南汀河断裂带的大地电磁测深宽频带阵列数据,利用大地电磁三维反演解释技术,首次获得了南汀河断裂带的精细三维深部电性结构.在上地壳深度,南汀河断裂带西南段与中段的电性结构表现出沿构造走向的高导条带特征,北东段表现为高阻结构.该高阻结构可能为临沧—勐海花岗岩体的电性反映,指示南汀河断裂可能未切穿该花岗岩带.在中下地壳深度,南汀河断裂带西南段存在大范围高导层,北东段则表现为整体性的高阻地壳,因此南汀河断裂北东段可能具有发生强震的介质结构背景.南汀河断裂带西南段的耿马地震区深部呈现北东向与北北西向的"X"型高导构造样式,该高导结构以南存在一个显著高阻异常体,1988年耿马M_S7.2地震以及2015年沧源M_S5.5级地震均发生于该高阻体与"X"型高导条带的电性边界.青藏高原东南缘绕东构造结流入滇西地区的中下地壳流可能受到南汀河断裂北东段中下地壳高阻体的阻挡而呈分流式分布于保山地块以及澜沧江断裂以东.     

青藏高原东缘龙门山逆冲构造深部电性结构特征

通过对汶川地震前观测的碌曲—若尔盖—北川—中江大地电磁剖面的数据处理和反演解释,揭示了沿剖面的松潘—甘孜地块、川西前陆盆地、龙门山构造带及秦岭构造带50 km深度的电性结构特征及相互关系,表明青藏高原东缘向东挤压,迫使向东流动的地壳物质沿高原东缘堆积,并向扬子陆块逆冲推覆.龙门山恰好位于松潘—甘孜地块与扬子陆块对挤部位,主要受松潘—甘孜地块壳内高导层滑脱和四川盆地基底高阻体阻挡的约束,地壳深部存在着西倾且连续展布的壳内低阻层,表明龙门山深部确实存在着逆冲推覆构造,其逆冲断裂系中的三条断裂不仅以不同的倾角向西北倾斜,并且向深部逐渐汇集,但茂县—汶川断裂可能在深部与北川—映秀断裂是分离的.龙门山两翼的四川盆地和松潘甘孜褶皱带的电性结构既具有明显差异性,又具有一定的相关性.四川盆地显示巨厚的低阻沉积盖层和连续稳定的高阻基底的二元电性结构,而松潘—甘孜地块则表现为反向二元结构,即上部大套高阻褶皱带,下部整体为低阻的变化带,龙门山逆冲构造带本身又表现为松潘地块逆冲上覆在四川盆地之上,构成上部高阻褶皱带、中部低阻逆冲断裂带和底部盆地高阻基底的三层电性结构.对比龙门山逆冲构造断裂带的西倾延伸上下盘两侧的两个反对称的二元电性结构,松潘区块深部推断的结晶基底与龙门山断裂带下盘推断的下伏盆地结晶基底又存在某种内在对应关系,推断可能存在一个西延至若尔盖地块的泛扬子陆块.因此,龙门山构造带地壳电性结构研究对于揭示青藏高原东缘陆内造山动力过程,探索汶川大地震的深部生成机理都具有重要意义.     

滇西龙陵地区地壳电性结构及其对大瑞铁路地质选线影响研究

高黎贡山地处印度板块与欧亚板块碰撞缝合带附近的横断山脉南段,是大理一瑞丽铁路(大瑞线)的必经之地,地形起伏大、构造复杂、活动性强,高黎贡山隧道作为全线控制性工程之一,其地质选线的最大困难就是对隧道深部构造环境的了解,特别是缺少对与地热、地震等联系紧密的深部地质构造的认识.为此,本文以大地电磁方法为手段,以高黎贡山隧道为主要研究对象,通过对滇西龙陵地区高黎贡山隧道越岭段两条大地电磁剖面数据的处理解释对研究区的地壳电性结构特征进行了勘探研究.结合区域地质构造特征与主要工程地质问题之间关系的分析,根据隧道主要断层地质条件设计了三维垂直断层模型,利用三维有限元开展正演模拟研究发现,测点点距、位置与横向分辨率密切相关,点距越密,分辨率越高,测点位于断层在地表投影位置能有效提高分辨率.采用大地电磁阻抗张量分解技术对两条剖面上各测点的二维偏离度和电性走向进行了计算和分析,对剖面视电阻率和阻抗相位数据进行了二维NLCG联合反演研究,揭示了沿剖面的腾冲地块、龙陵一瑞丽断裂带及保山地块10 km深度的电性结构特征及相互关系.结果表明:剖面CD电性结构呈现区域构造的三分性,腾冲地块电性结构成层性较好,保山地块成层性较差,两者均以中高阻电性特征为主,中间夹龙陵一瑞丽断裂带,电性结构反映从3 km深度以下存在几乎近于直立延伸的低阻带,推测为班公湖一怒江缝合带滇西段丁青一怒江缝合带的反映;剖面AB共划分了6条与工程密切相关的深部隐伏断裂,结合地震地质、地表地质及龙陵地震深部背景研究,推测F7-3断裂为1975龙陵7.3级地震断裂;从地表黄草坝断裂开始向下延伸,有一条发育最大深度约为4 km的低阻通道,推测为地热断裂深循环通道,其与黄草坝断裂共同控制研究区地下热水的补给、径流和排泄条件,在高黎贡山隧道线位位置形成了一个相对低温通道,为隧道方案成立的关键工程地质条件.勘探结果表明:滇西龙陵地区地壳电性结构有效的反映了高黎贡山隧道深部隐伏断裂和地热断裂深循环通道等深部构造特征,为大瑞线隧道工程地质选线提供了深部地质背景依据.     

云南南部地区深部电性结构特征研究

在云南南部地区布设了一条孟连-罗平的北东向大地电磁测深剖面,以开展该地区的深部电性结构探测和孕震环境探查.沿该剖面进行了114个大地电磁测深点的观测,经过对观测资料的远参考Robust处理、定性分析和二维反演,得到了沿该剖面地壳、上地幔电性结构模型,从模型的电性结构特征进一步探讨了剖面穿过的3个地震区的深部地震孕育环境.研究结果表明：沿剖面的地壳上地幔电性结构反映出与区域地质构造资料基本一致的构造特征;该区的三个强震带地球深部都存在壳内低阻体,地震发生在电阻率梯度带上;断裂带的两侧块体介质的电阻率差异是强震活动带重要的深部背景.     

华南地区樟树—宁德大地电磁测深剖面深部电性结构及热特征

华南地区武夷隆起带及东南沿海陆缘带具备中高温地热的储藏条件,而深部热源及热通道对于揭示中高温地热的形成机制至关重要.本文对江西樟树-福建宁德包含37个宽频测点的一条410 km长大地电磁测深剖面,采用非线性共轭梯度二维及三维反演,获得了岩石圈电性结构模型.研究发现,扬子地块东缘、武夷隆起带以及东南沿海陆缘带的电性结构存...     

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。     

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.     

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.     

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...