Petromagnetic and paleomagnetic study of Jurassic sedimentary rocks of the southeast of Russia

In the present paper the new petro- and paleomagnetic data on the Jurassic terrigenous complexes of the Mesozoic sedimentary basins of the Amur River region, Trans Baikal region, and Yakutia are presented. The magnetic properties of the sedimentary rocks of coastal-marine (paleo-shelf) and lake genesis are investigated in the contemporary intracontinental riftogenic Mesozoic superimposed troughs of the Siberian and Amur plates: the Chulmansk, the Unda-Dainsk, the Sredne-Amur, the Amuro-Zeisk, and the Verkhne-Bureinsk troughs. The statistically significant differences in the magnetic (anisotropic) characteristics of continental and marine deposits were inferred. The correlation of the scalar and tensor characteristics of magnetic susceptibility anisotropy and the parameters of its linearity, which depend indirectly on the intensity of the folding, is established. The preferential directions of regional stress during the fold formation are determined based on the analysis of the distribution of the axes of the tensor ellipsoid of the magnetic susceptibility anisotropy. The Jurassic positions of the paleomagnetic pole, which are close to the Mesozoic section of the trajectory of its apparent motion for the North Chinese plate and which differ from the Jurassic poles of the Siberian plate, are defined more accurately. The intraplate rotations of geoblocks within the limits of the amalgamated to the end of the Jurassic-to the beginning of the Cretaceous terrains as a part of the Amur tectonic plate are inferred. The calculated coordinates of the paleomagnetic pole indicate the larger than the present-day difference of the latitudinal positions of the southern part of the Siberian plate, and also of the Amur and North Chinese plates in the Early-Middle Jurassic time. This can be indicative of the fact that the total width of the shallow residual basins of the Paleo-Asian Ocean, which separated the geoblocks indicated in the Early-Middle Jurassic, attained the first thousands of kilometers, and/or such a difference in the paleolatitudes reflects the total value of the shortening (crowding) of the crust during the accretion and the fold formation. The time of the completion of the accretion of the terrains of the Amur and the North-Chinese plates and their attachment to the Siberian plate is not earlier than the end of the Late Jurassic-the beginning of the Cretaceous.     

斜腿夹角对V形墩连续刚构桥地震响应的影响研究

为研究斜腿夹角对V形墩连续刚构桥地震响应的影响及合理斜腿夹角角度，以一座典型V形墩预应力混凝土连续刚构桥为研究对象，采用有限元分析方法研究了斜腿夹角θ对桥梁内力及位移的影响，得出了θ对结构地震响应的影响规律和变化曲线。研究结果表明:随着斜腿夹角的增加，在纵向地震力作用下，墩底纵向弯矩逐渐减小，墩顶和主梁墩顶支撑处纵向弯矩逐渐增大；在横向地震力作用下，跨中横向弯矩逐渐减小，墩底横向弯矩逐渐增大，墩顶横向弯矩基本不变；在竖向地震力作用下，墩底和墩顶竖向弯矩逐渐增大，主梁支撑处竖向弯矩逐渐减小；斜腿夹角对纵向或横向地震力作用下结构位移影响不大，对竖向地震力作用下的位移影响较大。在满足静力设计的前提下，当两斜腿夹角为90°时，结构地震响应相对较小，受力合理性最优。研究成果可为该类桥梁的抗震设计与斜腿夹角角度选取提供参考和依据。     

Assessment of seismic hazard of the Japanese islands based on fractal analysis of GPS time series

Based on the fractal analysis of the time series of the Earth’s surface vertical displacements in the region of the Japanese Archipelago, the maps of the estimates of seismic activity in the region over 2015 are constructed. The analysis of the maps revealed several segments of the territory which are prone to the emergence of significant earthquakes. The characteristic peculiarity is noted in the change of the behavior of the geophysical dynamic system—the Earth’s crust—before the occurrence of seismic events: the mechanism of transition to the critical state demonstrates the energy preservation of the low frequencies with the simultaneous energy decay of the middle and high frequencies, which differs from the behavior of the other dynamical systems.     

Propagation of radio waves reflected from the ionosphere during a solar eclipse

Summary The article first describes in chronological order the observations on the propagation of radio waves during the solar eclipses, and the development of the conflicting results on the similar transmissions of radio signals. The general theory of the absorption of radio waves in the ionosphere is briefly described and therefrom a method is derived to estimate the variation of the absorption of obliquely incident radio waves during a solar eclipse.The variation of field-strength can be studied in terms of the relationship between the vertical incident equivalent frequency of the signals and the critical frequencies of the ionospheric layers at the regions of reflection. The total absorption of radio waves consists of the non-deviative absorption in theD region and the deviative absorption in the higher layers of the ionosphere. During the eclipse, theD region absorption decreases in phase with the progress of the eclipse, but the variation of deviative absorption may differ in each observation. The deviative absorption is large when the equivalent frequency is close to the critical frequency of the layer reflecting the waves or of the layer just penetrated by the waves. The changes in the deviative absorption during an eclipse can be estimated on the basis of the variation of the critical frequencies of the ionospheric layers. The resultant changes in the total absorption during a solar eclipse may thus be estimated. The different types of field strength variation expected during an eclipse are given.The observations of the vertical incident absorption of radio waves and the field strength variations of obliquely incident continuous wave radio signals during the solar eclipse are described and the changes are explained on the basis of the above theory.     

The degree of astaticism of an astatic magnetometer

Summary The degree of astaticism is the fundamental parameter of an astatic magnetometer, an instrument used in geophysics for magnetic measurements of rock specimens. The degree of astaticism is formulated with a view to the vectorial character of the defining quantities and with a view to the effect of the geomagnetic field. As regards measuring the parameter, the mirror method is given, which makes use of the positive and negative orientation of the astatic system relative to the north or east. The measure of the value of the parameter is the change of the sensitivity of the system and the deflection of its zero position, compensated for by the magnetic field of the calibration coil. The problem of the degree of astaticism is treated complexly, inclusive of the measurement of the parameter, which in practice is of fundamental importance for adjusting the systems for manufacturing astatic magnetometers.     

半空间异质隆起的出平面动力响应:地表运动

采用闭合解析解对水平地表圆形非匀质隆起出平面运动特征进行详细分析。结果表明：（1）隆起区域介质软硬程度对其出平面地表运动影响非常大，软质隆起表面的地表位移较匀质隆起情况有显著放大，地表运动波动效应明显增强，而硬质隆起则减弱地表运动；（2）软质隆起地表位移幅值最大反应和平均反应增大的程度一般来说至少不低于隆起区域波速降低的程度，很多情况是远大于波速降低的程度，但最大反应出现的位置和频段主要受入射波角度控制；（3）当波垂直传播时，地表位移放大出现在隆起顶部，频率随隆起区变软，明显向低频移动，可出现在很低频段内，且随隆起区变软放大更为显著；（4）当波掠入射时，地表最大位移出现在隆起后表面，地表运动仍然十分强烈，甚至比波垂直入射时隆起顶部反应还要大，但出现在较高频段内。     

Optimization of the Shape of Gaussian Beams of a Fixed Length

The procedure of choosing the shape of Gaussian beams in order to minimize a given object function of a certain kind is proposed. The general form of the object function enables both the average square of the quadratic variation of the phase and the average square of the beamwidth to be minimized along the central ray. The error of the transformation of the Gaussian beams at the structural interfaces may also be taken into account. Most of the hitherto published suggestions of how to chose the shape of Gaussian beams are special cases of the described procedure. The aim of this paper is not to propose the object function to be minimized, but only to describe the minimization of a given object function. The minimization assumes the a priori known lengths of the central rays of the Gaussian beams (i.e. the lengths of the beams are not free parameters in the minimization procedure).     

不同单轴加压方式下岩石声发射的时间过程与频率特征

本文利用两个频率通道同时接收花岗岩标本及石灰岩标本在不同单轴加压方式下的声发射信号,研究了从加压到破坏的整个形变过程中,不同频道接收到的声发射率的变化特征.发现在各种加压方式下,花岗岩和石灰岩在破坏前,由不同频率通道接收到的声发射率均急剧增长;而在破坏的瞬间,高频通道接收的声发射率增长快于较低频率通道的声发射率.这两点可用来预测岩石的破坏.声发射率随轴向应力的变化与加压方式有关.匀速加压,加压过程中保持一段时间恒压或降压均对应一定的声发射率状态.有可能通过追踪声发射情况,推测应力变化趋势.      

1977年5月12日宁河地震烈度明显偏低的探讨

1977年5月12日宁河6.6级地震的震中烈度较之震级相当的其他地震的震中烈度明显地偏低。为了阐明这种现象,由P波初动半周期及振幅求得了该区不同时期内的品质因数（Q值）及小震震源参数,并重新校对了这次地震以及1976年11月15日宁河6.9级地震的宏观及微观参数。分析结果表明:这次地震震中烈度异常低是因为1976年11月15日6.9级地震后,该区介质的品质因数大幅度下降,同时这个地震的震源深度比6.9级地震的震源深度约深5公里。品质因数和震源深度的综合效应可导致震中烈度降低近一度。     

Temporal variations in the tidal response of the medium in the vicinities of the sources of catastrophic earthquakes

The idea of predicting earthquakes by continuously monitoring temporal variations in the tidal response of the medium was suggested by Beaumont and Berger in 1974. However, it became possible to implement the idea only recently. This possibility has arisen due to the deployment of Global Seismic Network (GSN), which collects the data on tidal tilts and gravity in the epicenters of strong earthquakes before and after the strongest events. In this paper, we present the results of model analytical and numerical calculations of the elastic displacements of the Earth??s surface caused by the earthquakes and their preparatory processes. The analytical calculations are limited to the model of a uniform elastic halfspace; the numerical calculations, in addition to this model, also cover the models with radially heterogeneous distributions of elastic moduli in the crust and in the upper mantle, which are determined by the PREM model. We describe the results of modeling temporal variations in the tidal response of the medium in the vicinity of the source of a catastrophic earthquake. The model of seismic source is specified by the length and the orientations of the fault plane and by the value of the discontinuity in the tangential component of the displacement vector on the opposite sides of the fault. The model is based on the GPS data on the horizontal and vertical displacements of the Earth??s surface. We suggest the method for determining temporal changes in the tidal response of the medium in the seismically active regions. This method improves the sensitivity and time resolution of the standard techniques of sliding-window analysis by more than an order of magnitude. The comparative analysis of temporal variations in the tidal response of the medium in the zones of the magnitude 9 earthquake in Japan (March 9, 2011) illustrates the described approach.     

Temporal variations in the tidal response of the medium in the vicinities of the sources of catastrophic earthquakes

The idea of predicting earthquakes by continuously monitoring temporal variations in the tidal response of the medium was suggested by Beaumont and Berger in 1974. However, it became possible to implement the idea only recently. This possibility has arisen due to the deployment of Global Seismic Network (GSN), which collects the data on tidal tilts and gravity in the epicenters of strong earthquakes before and after the strongest events. In this paper, we present the results of model analytical and numerical calculations of the elastic displacements of the Earth’s surface caused by the earthquakes and their preparatory processes. The analytical calculations are limited to the model of a uniform elastic halfspace; the numerical calculations, in addition to this model, also cover the models with radially heterogeneous distributions of elastic moduli in the crust and in the upper mantle, which are determined by the PREM model. We describe the results of modeling temporal variations in the tidal response of the medium in the vicinity of the source of a catastrophic earthquake. The model of seismic source is specified by the length and the orientations of the fault plane and by the value of the discontinuity in the tangential component of the displacement vector on the opposite sides of the fault. The model is based on the GPS data on the horizontal and vertical displacements of the Earth’s surface. We suggest the method for determining temporal changes in the tidal response of the medium in the seismically active regions. This method improves the sensitivity and time resolution of the standard techniques of sliding-window analysis by more than an order of magnitude. The comparative analysis of temporal variations in the tidal response of the medium in the zones of the magnitude 9 earthquake in Japan (March 9, 2011) illustrates the described approach.

     

Allowance for motion in a steady-state thermal flux pattern

The correlation between the pulsed and smooth components of ultraviolet radiation and hard X-rays from solar flares has been interpreted on the basis of the time behavior of the energy flux penetrating from the magnetic field reconnection region to the boundary of the heated region. It has been shown that the time behavior of the primary flare energy flux is easily reconstructed from the time profile of the intensity of hard X-rays, and the time profile of the intensity of ultraviolet radiation represents the release of the flare energy in the flare transient layer. The smooth or pulsed component of the ultraviolet radiation depends on the form of the primary energy release. Information on the dynamics of the heating process and the formation and equalization of the gas pressure in the flare transient layer has been obtained from the observed temperature dependence of the emission measure. The described scheme explains the set of flare phenomena and the correlation between hard X-rays with pulsed ultraviolet bursts.     

洞庭湖近几十年来湖盆变化及冲淤特征

洞庭湖是我国著名的五大淡水湖泊之一,位于长江中游荆江段南岸,湖南省境内.历史时期,曾经是我国第一大淡水湖,直至新中国成立初期,湖泊面积仍然有4350km2,居我国淡水湖泊之首位.但由于洞庭湖承纳“四水”,吞吐长江,长江大量水沙涌入洞庭湖,造成了湖盆迅速淤高,加之由此诱发的人类大规模地湖泊垦殖活动,湖泊急剧萎缩.目前,洞庭湖已退居鄱阳湖之后,为我国第二大淡水湖泊.湖泊的严重泥沙淤积,已经造成了湖泊调蓄长江中游洪水功能的严重衰退,不但危及湖南省的防洪的安全,而且危及长江中下游地区的防洪安全,研究洞庭湖的湖盆冲淤演变具有重要意义.本文根据1974、1988和1998年洞庭湖125000水下地形资料,并针对洞庭湖具有显著上下游水位落差的实际,分不同高程和不同水位情况下,分析洞庭湖湖泊面积和容积演变特征,探讨洞庭湖近几十年来的湖盆变化及冲淤规律,试图揭示洞庭湖湖泊调蓄能力的变化过程.     

Fluid regime in the source and preparation area of an earthquake

Peculiarities of the fluid regime in the source and in the area of preparation of an earthquake which accommodates the evolution of the precursors are considered. The qualitative characteristics and the conditions of migration of the fluids, as well as their influence on the disjunctive deformations of the crust are discussed. During the development of the earthquake source, the fluid regime in this area depends on the redistribution of the fluids and their inflow from the outside. The fluid inflow and the increase in the fluid pressure are mainly due to the filtering from the subvertical permeable faults and the metamorphic dehydration of the rocks in the walls of the main fault. The fluids may also be supplied to the source from the near-surface horizons, and most of the induced earthquakes are associated with this process. These earthquakes can be considered as large-scale natural experiments which can shed light on the contribution of fluids in this phenomenon. A particular role in the mechanism of natural seismicity is played by the inflow of high-pressure fluids through the faults from the deep zones of the section.     

Generalized Solutions of the Inverse Problem and New Technologies for the Quantitative Interpretation of Gravity Anomalies

The approach, fundamentally different from the known ones, to estimating the spatial location of the domain filled with the disturbing masses based on the gravity field measurement data is suggested. The main idea of the approach is, using the set of the probable variants of the interpretation, to construct the distribution of a certain parameter associated with the estimate of probability of detecting the sources of the field in any point of the studied geological medium and then to apply this distribution to each domain eligible for being the true carrier of the anomalous masses. These constructions yield the generalized admissible solutions of the inverse problem with ranking the separate fragments of the model carrier in terms of the probability of detecting anomalous masses in them.     

全球扰动场源的研究及其大地构造意义

作为大地重力学反问题研究的实际应用，本文计算了全球扰动场源．在参数选择、赋值模式上，首先考虑到地球的成层结构与密度异常分布．研究表明，地球内部物质分布的不均一性主要体现在岩石层块体内部，并一直延深到幔核边界；地壳中的构造活动与地球内部物质分布状态相关．从大地构造学的角度，分析对比讨论了扰动场源所揭示的地球深部地质作用机理．     

隧道磁共振测深超前探测模型参数不确定度分析方法研究

地面磁共振方法探测地下水趋于成熟.随着研究的深入,磁共振技术在隧道超前探测方面也开展了应用.然而,由于隧道空间特殊环境限制,获取的磁共振信号信噪比极低,解释结果中各参数的确定性值得深思.基于这一问题,本文提出隧道磁共振测深超前探测模型参数不确定度分析方案,实际工作前,根据不同探测目标要求及环境噪声水平,优化仪器装置参数设计,提高解释结果准确性.本文首先在地面磁共振探测理论基础上,推导了考虑天线铺设角度影响的隧道矩形线圈激发场计算表达式,模拟了隧道准全空间磁共振测深正演响应.其次,基于后验模型协方差矩阵,计算模型参数标准偏差因子,划分参数不确定度等级.最后,构建三层含水模型,将第二层含水体作为观测目标.在仿真合成数据的基础上,分别探讨了电阻率、含水量、水体厚度、线圈边长、匝数、线圈旋转角度以及噪声水平等参数对目标含水体测定的影响.通过对比分析,得到如下结论：当探测目标前方地层的电阻率小于10 Ωm时,目标含水体的不确定度随着该电阻率的增大而降低;当该电阻率大于10 Ωm时,其不影响目标含水体的不确定度;目标体前方地层含水量的增大能够明显增加目标含水体的不确定度;目标层电阻率以及含水量对该层含水体的不确定度几乎不造成影响;目标层厚度越大其含水体的确定度越高;线圈边长和匝数的增大都能在很大程度上降低含水体的不确定度;线圈的偏转角度不影响目标体的不确定度;磁共振信号中噪声的幅度越大,含水体参数的不确定度越大.本文的研究结论有助于提高隧道磁共振探测数据反演参数的准确性,同时能够为实际探测提供预先优化参数的分析方案.     

六盘山东麓地区活动构造研究

该文介绍了六盘山东麓地区活动构造研究的主要研究内容,包括：六盘山东麓断裂第四纪以来的活动特征、六盘山东麓断裂的变形幅度与位错速率、古地震事件及六盘山东麓断裂带的分段性。     

Estimation of deformational properties of a stratum-borehole system based on analysis of barometric and tidal responses of the water level in a borehole

Statically isolated conditions in the stratum-borehole hydrogeological system under consideration at periods of ≥ 3 h are established on the basis of the investigation of barometric and tidal responses of the water level in a borehole located in the territory of the Mikhnevo Geophysical Observatory, Institute of Geosphere Dynamics, Russian Academy of Sciences. The barometric effectiveness, tidal sensitivity of the water level, elastic parameters, and porosity of water-bearing rocks are estimated. A model of the inertial character of the water exchange in the stratum-borehole system is constructed depending on the period of variations with allowance for the borehole design, as well as the water transmissibility and elastic capacity of the aquifer. The results of modeling are in compliance with the dependence of the amplitude transfer function from variations in the atmospheric pressure to variations in the water level. The results of processing the data of high-precision measurements made it possible to refine the transmissibility of the aquifer obtained from the data of experimental filtration works.