甚低频/低频人工源电波信号地震应用研究进展

甚低频/低频人工源电波作为一种主动源发射的通讯导航信号,因其长距离波导传播的特性在地-电离层观测及应用中表现出极大的优势.本文总结了二十世纪末以来基于甚低频/低频(VLF/LF)电波观测技术及其数据分析方法、典型震例及统计研究成果、圈层耦合机理等方面的研究进展,并通过探讨其应用成果的快速积累及前兆扰动起源等研究难点,展...     

武汉地区中尺度电离层声重波扰动的变化特性

利用武汉电离层观象台高频多普勒台阵的覆盖太阳活动高、低年份,长达５年的连续观测数据,采用小波分析等方法估算电离层声重波扰动（ＴＩＤ）的传播参量,通过这些参量对武汉地区电离层扰动形态和变化规律进行了系统分析研究．结果表明,观测到的中尺度电离层声重波扰动（ＭＳＴＩＤ）存在二个显著季变化,在传播速度和周期上有明显差异的优势传播方向：一个指向东北方,传播的方位角主要分布在３０°─７０°之间（０°为正北,以顺时针方向表示传播方位角）,它在夏季出现率最大,冬季基本消失;另一个优势方向指向正南,方位角主要分布在１５０°─２２０°范围,主要出现在冬季．文中还给出了ＭＳＴＩＤ的年、日变化,并进一步探讨了其变化特性的可能形成机理．     

武汉地区中尺度电离层声重波扰动的变化特性

利用武汉电离层观象台高频多普勒台阵的覆盖太阳活动高、低年份，长达５年的连续观测数据，采用小波分析等方法估算电离层声重波扰动（ＴＩＤ）的传播参量，通过这些参量对武汉地区电离层扰动形态和变化规律进行了系统分析研究．结果表明，观测到的中尺度电离层声重波扰动（ＭＳＴＩＤ）存在二个显著季变化，在传播速度和周期上有明显差异的优势传播方向：一个指向东北方，传播的方位角主要分布在３０°─７０°之间（０°为正北，以顺时针方向表示传播方位角），它在夏季出现率最大，冬季基本消失；另一个优势方向指向正南，方位角主要分布在１５０°─２２０°范围，主要出现在冬季．文中还给出了ＭＳＴＩＤ的年、日变化，并进一步探讨了其变化特性的可能形成机理．     

汶川地震同震电离层扰动研究

利用中国大陆陆态观测网(CMONOC)的下关、 昆明和庐州GPS台站, 对汶川地震引起的同震电离层扰动(CID)进行研究。 通过对GPS原始观测数据进行处理证实汶川地震存在5个明显的同震电离层扰动(CID)现象。 根据GPS TEC时间序列和走时, 得到在电离层高度CID的水平传播速度为1.1 km/s, 属于震中区地表抬升引起的声波在电离层中传播速度; 同时, 也得到次一级CID传播速度接近0.7 km/s, 认为可能是重力波。 在此基础上, 利用射线追踪模型寻找震中位置发现, 当CID水平传播速度为1000 m/s时, 发震时刻对应的标准偏差能达到最小值19.55 s, 相应的CID起源位置是30.8°N, 103.15°E, 距离实际震中西南方向33.6 km。     

电离层对台风响应的全过程的特例研究

作为特例研究,本文对1988年和1990年两次强台风影响期间的电离层多普勒记录及相应的台风资料进行了细致的相关分析,目的是利用多普勒记录的连续性优点来了解电离层对登陆（或近海）强台风通过声重波响应的演化全过程.分析表明,在这两次台风影响期间,电离层形态中除有明显的波状扰动（中尺度声重波）出现外,还有一些值得注意的新现象：波动的时间演化表现出明显的幅度逐渐增加以及频率由高频向低频转变,在振幅很大的情况下日落后同时出现扩展F（Spread-F）现象,显示了声重波在激发电离层不规则结构方面的种子作用.这一演化过程与电离层中TIDs的线性传播理论一致,文中开展了对这一现象的非线性数值模拟,模拟结果基本上也与上述观测现象相吻合.     

用数字测高仪漂移测量研究电离层声重波扰动

数字测高仪Digisonde中的漂移测量,常用来研究小尺度电离层扰动,如电离层小不均匀体的漂移。文中提出一种新的分析方法,利用漂移测量数据中多普勒频移和到达角参量的最大熵动态功率谱,估算声重波一类大尺度电离层扰动的水平传播速度和传播方向。作为实例,研究了Millstone Hill测高仪站的漂移观测资料,并对处理结果进行了初步分析。分析结果表明,从数字测高仪漂移测量数据中,可有效地提取声重波一类大尺度电离层扰动的传播参量,在电离层动力过程的研究中很有意义。     

用数字测高仪漂移测量研究电离层声重波扰动

数字测高仪Digisonde中的漂移测量,常用来研究小尺度电离层扰动,如电离层小不均匀体的漂移。文中提出一种新的分析方法,利用漂移测量数据中多普勒频移和到达角参量的最大熵动态功率谱,估算声重波一类大尺度电离层扰动的水平传播速度和传播方向。作为实例,研究了Millstone Hill测高仪站的漂移观测资料,并对处理结果进行了初步分析。分析结果表明,从数字测高仪漂移测量数据中,可有效地提取声重波一类大尺度电离层扰动的传播参量,在电离层动力过程的研究中很有意义。     

基于张衡一号卫星监测的2021年青海玛多7.4级地震前电离层效应

本次研究围绕张衡一号(ZH-1)卫星监测到的2021年青海玛多M_S7.4地震前的电离层效应,采用上下四分位距法和小波变换法处理ZH-1卫星朗缪尔探针(LAP)探测到的电子密度N_e和等离子体分析仪(PAP)探测到的离子密度N_i(He⁺和O⁺)数据,经分析发现N_e、 He⁺密度和O⁺密度在震前7天(2021年5月14日)和5天(2021年5月16日)出现同步异常。在此基础上,基于地球物理异常多项证据,分析认为2021年玛多M_S7.4地震孕育过程包括应力扩张早期、应力扩张晚期和临震加速期,该地震可能通过岩石圈—大气圈—电离层耦合模型的声重波、电磁波通道影响了电离层。     

地球表层特征参量反演与模拟的机理-学习耦合范式

构建物理驱动的机理模型一直是估算地球表层特征参量的核心科学范式,发展数据驱动的机器学习模型是地学研究范式转换的重要途径,而耦合机理模型与学习模型则可以实现“理性主义”与“经验主义”的结合,是当前最受关注的研究热点之一.文章针对参量估算的遥感反演与动力学模拟方法,深入分析了机理模型与学习模型的内在瓶颈及其互补性,搭建了以机理级联学习、学习嵌入机理、机理融进学习为核心的耦合范式框架,归纳了预处理与初始化、中间变量传递、后置精化处理、模型替代、模型调整、模型求解、输入变量约束、目标函数约束、模型结构约束、混合应用等十种具体耦合方式,剖析了当前的主要问题与未来的挑战方向.研究为深入理解、应用机理-学习耦合模型提供了新视角,为提升地球表层特征参量反演与模拟能力、服务地球系统科学发展提供理论与技术支撑.     

暴时场向电流及磁层—电离层耦合过程

本文综述了不同类型电离层场向电流(亦称为Birkeland电流)及其在地磁扰动(磁暴和亚暴)期间的时空分布特征.首先简述了场向电流近70年的研究历程,总结了各种与太阳风—行星际磁场(interplanetary magnetic field,IMF)、电离层电导率空间分布不均匀相关的1区和2区场向电流,北向、晨昏向IM...     

地震电离层探测技术及其应用研究进展

2017年即将发射的中国电磁监测试验卫星将填补地震电离层立体监测体系中不可或缺的空白区域,也将为天地一体化地震电磁对比校验及圈层耦合机理认识提供重要的科学支撑.针对近期地震电离层立体监测体系发展的需求,本文主要介绍了目前国内用于地震研究的地基及空基电离层探测技术,包括电离层垂测/斜测、甚低频(VLF)电波观测、舒曼谐振观测、GPS及空间卫星电磁等,并总结了各种探测技术在国内外地震应用研究中的进展; 最后结合不同探测手段的优势,探讨了地震电磁立体探测系统的构建,并就未来的多手段综合应用发展提出了建议.      

基于Swarm卫星数据的一次地震电离层现象辨识

为进一步探索基于多颗卫星观测数据的地震电离层现象识别,利用Swarm星座三颗卫星观测的电子密度数据和磁场数据,对已报道的2017年11月12日伊朗MW7.3地震震前第9天震中附近的一次地震电离层扰动现象进行辨识。通过分析三颗卫星相邻轨道的电离层扰动特征,获得了异常扰动存在的空间范围;利用Swarm星座三颗卫星轨道的时间和空间差异,计算出异常扰动在空间中可能的传播特征;使用同步观测的磁场数据判断其电磁辐射特性。最终根据现有对地震电离层耦合的认知,并结合分析的结果,认为该扰动为非震源发出的声重波扰动,非沿纬向传播的电离层行波扰动,非同步电磁辐射引发扰动,而是与伊朗MW7.3地震孕育活动无关的一次高纬度强烈电离层活动所引起的扰动变化。     

岩石层—大气层—电离层耦合作为震前大气层和电离层短临事件的影响机制

介绍了大气层和电离层震前现象机制的基本观念。简短回顾了观测结果后,我们得出结论：1．流体下层物质（气泡）向上迁移能导致近地表的热水／气体被逐出,并在强度弱化的地区引发地震;2．因此,气泡出现的时间和地点是随机的,但是地震、地球化学异常和前震（地震、SA和超低频电磁异常）是随机关联的;3．大气温度和密度扰动跟随着震前热水／气体释放,导致产生周期为6～60min的大气重力波（AGW）;4．地震引发的大气重力波能导致电离层扰动变化并导致大气层中地平线上无线电波传播、下部电离层低频波扰动和地面超低频辐射衰减的变化。     

秦岭造山带上地幔各向异性及相关的壳幔耦合型式

秦岭是具有复杂地壳结构、经历长期构造演化的复合型大陆造山带.本文通过地震资料精细反演上地幔各向异性,探索秦岭造山带构造演化及成因动力.采用最小切向能量法、最小特征值法和"叠加"分析法求得覆盖秦岭造山带及周边地区41个地震台站的SKS横波分裂结果：快波偏振方向(φ)和快、慢波的时间延迟(δt),据此绘制了秦岭造山带上地幔各向异性图.将已发表的地表GPS观测结果与上地幔各向异性相结合作上地幔变形因素分析,发现秦岭造山带自西向东的上地幔变形因素不是单一垂直连贯变形或地幔流动,而是共存的.同时,其上地幔变形的主控因素有区域性变化.研究表明秦岭造山带西、中部上地幔变形以壳幔垂直连贯变形为主,属壳幔强耦合,东部壳、幔耦合变弱,上地幔变形以简单地幔流动为主控因素.同时,SKS快波偏振方向(φ)于秦岭造山带显示出南缘略向北凸、北缘略向南凸的弧形展布,反映了造山带两侧刚性较强的扬子地块与鄂尔多斯地块旋转与秦岭造山带南北缘弧形流动有关.     

Characteristics and mechanism of vertical coupling in the genesis of tropical cyclone Durian(2001)

The vertical coupling(VC)process and mechanism during the genesis of a tropical cyclone(TC)implied by the weak vertical shear of horizontal wind,one of the key factors impacting TC genesis,constitute important but unanswered fundamental scientific problems.This paper carried out a targeted investigation of this problem through numerical simulation and theoretical analyses.The main conclusions are as follows.Even if TC genesis occurs in a barotropic environment,a VC process still occurs between the trough(vortex)at the middle level and that at the lower level in the TC embryo area.VC mainly occurs at the tropical disturbance(TDS)stage.Only after the VC is accomplished can the tropical depression(TD)organize further by itself and develop into the tropical storm(TS)stage or the stronger tropical typhoon(TY)stage through the WISHE(wind-induced surface heat exchange)mechanism.In the VC process,vortical hot towers(VHTs)play vertical connecting roles and are the actual practitioners of the VC.Through the VHTs’vertical connections,the middle-and lower-troposphere trough axes move towards each other and realize the VC.VHTs can produce intensive cyclonic vorticity in the lower troposphere,which is mainly contributed by the stretching term.The tilting term can produce a single dipole or double dipole of vorticity,but the positive and negative vorticity pairs offset each other roughly.While the stretching term ensures that the cyclonic rotations of the wind field in the middle and lower levels tend to be consistent,the tilting term acts to uniformly distribute the horizontal wind in the vertical direction,and both terms facilitate the VC of the wind field.With the latent heat of condensation,VHTs heat the upper and middle troposphere so that the 352 K equivalent potential temperature contour penetrates vertically into the 925–300 hPa layer,realizing the VC of the temperature field.While forming cloud towers,VHTs make the ambient air become moist and nearly saturated so that the 95%relative humidity contour penetrates vertically into the 925–400 hPa layer,realizing the VC of the humidity field.Due to the collective contributions of the VHTs,the embryo area develops into a warm,nearly saturated core with strong cyclonic vorticity.The barotropic instability mechanism may also occur during TC genesis over the Northwest Pacific and provide rich large-scale environmental vorticity for TC genesis.The axisymmetric distribution of VHTs is an important sign of TC genesis.When a TC is about to form,there may be accompanying phenomena between the axisymmetric process of VHTs and vortex Rossby waves.     

A new mechanism of atmospheric CO2 absorption promoted by iron-nitrogen coupling in low-latitude oceans during ice age

It has been confirmed by a large number of studies that iron can significantly improve the carbon fixation level in the high-latitude oceans (Martinez-Garcia et al., 2014). Although there are many studies on the mechanism of ironcarbon coupling in the modem ocean, the research on ironnitrogen-carbon coupling is rare (Tagliabue et al., 2014;Song, 2010). It is of great significance for the prediction of future ocean changes to identify the key processes of modem ocean and analyze the past ocean changes.     

Analysis on the coupling law between economic development and the environment in Ürümqi city

The inter-coupling relationship between urban economic development and the ecological environment refers to the total of interactive, inter-influenced and other non-linear relations between economic and environmental systems in the course of economic development. Taking Ürümqi, an oasis city in arid region, as an example, we collected the data of environmental quality & pollutants discharge and information on economic development in the 20 years, analyzed the correlation between the two, conducted a fitted regression with quadratic and cubic equations, and acquired 14 mathematic models that could describe the relationship between the environment and economic development. The results show that there exists a coordinated and interactive relationship between the environment and economic development. On the basis of these quantity analyses, conceptional frame model is built to explain the fundamental basis of this environmental coupling in Ürümqi city. Both a quantitative analysis of the coupling law and a good command of the internal law between them are useful for making comprehensive decisions about the environment and economic development and harmonizing the urban sustainable development.     

The effects of torsion and motion coupling in site response estimation

Soil amplification characteristics are investigated using data from the Chibaken‐Toho‐Oki earthquake and its aftershocks recorded at Chiba dense array in Japan. The frequency‐dependent amplification function of soil is calculated using uphole‐to‐downhole spectral ratio analysis, considering the horizontal components of shear wave. The identified spectral ratios consistently demonstrate the splitting of peaks in their resonance frequencies and low amplification values in comparison with a 1D model. The torsional behaviour and horizontal ground motion coupling are clarified as the reasons for these phenomena at the site. To prove the hypothesis, the torsional motion is directly evaluated using the data of the horizontal dense array in different depths at the site. The comparison between Fourier spectra of torsional motion and identified transfer functions reveals the peaks at the same frequencies. The wave equation including torsion and horizontal motion coupling is introduced and solved for the layered media by applying wave propagation theory. Using the developed model, the effects of torsional motion with horizontal motion coupling on soil transfer function are numerically examined. Splitting and low amplification at resonance frequencies are confirmed by the results of numerical analysis. Furthermore, the ground motion in two horizontal directions at the site is simulated using site geotechnical specification and optimizing the model parameters. The simulated and recorded motions demonstrate good agreement that is used to validate the hypothesis. In addition, the spectral density of torsional ground motions are compared with the calculated one and found to be well predicted by the model. Finally, the results are used to explain the overestimation of damping in back‐calculation of dynamic soil properties using vertical array data in small strain level. Copyright © 2003 John Wiley & Sons, Ltd.     

Theorem of turbulent intensity and macroscopic mechanism of the turbulence development

Turbulence is one of the most common nature phenomena in everyday experience, but that is not adequately understood yet. This article reviews the history and present state of development of the turbulence theory and indicates the necessity to probe into the turbulent features and mechanism with the different methods at different levels. Therefore this article proves a theorem of turbulent transpor- tation and a theorem of turbulent intensity by using the theory of the nonequilibrium thermodynamics, and that the Reynolds turbulence and the Rayleigh-Bénard turbulence are united in the theorems of the turbulent intensity and the turbulent transportation. The macroscopic cause of the development of fluid turbulence is a result from shearing effect of the velocity together with the temperature, which is also the macroscopic cause of the stretch and fold of trajectory in the phase space of turbulent field. And it is proved by the observed data of atmosphere that the phenomenological coefficient of turbulent in- tensity is not only a function of the velocity shear but also a function of temperature shear, viz the sta- bility of temperature stratification, in the atmosphere. Accordingly, authenticity of the theorem, which is proved by the theory of nonequilibrium thermodynamics, of turbulent intensity is testified by the facts of observational experiment.