Lagrangian Solution of Dynamo Equations and Path Integrals

We discuss an explicit solution of the Cauchy problem for induction equation and suggest its generalization for equations of ²-dynamo. These solutions are based on concepts of multiplicative, Wiener path, and stochastic integrals. Obtained explicit solution can be useful as a tool in investigations of a dynamo with fluctuating helicity.     

云南孟连西7.3级、武定6.5级、丽江7.0级三次强震前地震波振幅比的时空演化特征

１９９５年７月１２日至１９９６年２月３日短短７个月,云南地区连续发生了孟连西中缅边境７．３级、武定５．５级、丽江７．０级３次强震,本文研究了近期这几次强震前５个地震台地震图垂直分量Ｓ、Ｐ波最大振幅比的时空演化特征,动态追踪了振幅比明显偏离平稳态的突变过程。发现主震前５—８年,７级大震震中１００ｋｍ范围出现振幅比高（低）值突变,６级强震震中１３０ｋｍ范围出现振幅比高值突变,当振幅比的突变在缓升（降）的背景上骤升（降）,或突变异常的地震次数明显增加,则中长期异常进入中短期阶段。在强震震中１３０ｋｍ范围内的地震台（近台）振幅比值高达１５．２以上,而远离强震震中２５０ｋｍ以外的地震台（远台）振幅比最大值仅为９．８,近台的突变幅度至少比远台大３０％。而强震成组发生前一年半时间内,位于强震震中１１０ｋｍ范围内的近台振幅比的突变幅度比远在２５０ｋｍ外远台大５５—７５％。对振幅比的突变和时空演化特征从非线性动力学模型和模拟实验结果进行了初步成因探讨。     

穿过张家口—渤海地震带西缘的折射剖面所揭示的地壳上地幔构造与速度结构

近期完成的北北东向的繁峙～太仆寺旗宽角反射／折射剖面,由山西断隆进入内蒙地轴,它穿过了山西地震带的大同～阳高震区和北西西向张家口～渤海地震带的西北缘。其主要目的是探测研究张～渤地震带及其两侧壳幔构造与速度结构的差异及其与地震活动的相关性。结果表明：张～渤地震带壳内界面及莫霍面较其两侧有１．０～２．０ｋｍ的不同程度的上隆;在阳原～张家口之间地壳结构纵向与横向非均匀性明显,上地壳和下地壳上部有局部的速度逆转,下地壳下部的低速层由山西断隆一直延伸至内蒙地轴,上地幔顶部的速度梯度明显增大;在阳原、怀安和张北附近分别存在着延伸至莫霍面的地壳深断裂带;在内蒙地轴一系列壳内界面不明显。     

基于小波变换的信号突变检测滤波和瞬态谱研究

该文简述了小波理论产生的背景和发展过程,详细介绍了小波变换的概念、基本特性以及基于小波变换的信号突变检测、滤波及基于小波包变换的瞬态谱研究方法和结果。文后对小波变换在地震信号处理中的应用前景进行了讨论。     

On the use of microtremor recordings in seismic microzonation

Experimental methods involving microtremor recordings are useful for determining site effects in regions of moderate seismic activity where ground motion records are few, and in urban or industrial contexts where the noise level is high. The aim of this study is to establish a microzonation by using the Nogoshi–Nakamura method,[1, 2] a simple experimental technique based on microtremor recordings. Since the physical phenomena underlying the method are only partially understood, the spectral responses obtained cannot be used alone. We, therefore, complete our experimental results by comparing them with the solutions of a one-dimensional numerical simulation (SHAKE91).[3, 4] The experimental programme was carried out on a plain near the Rhone Delta (South of France). H/V spectral ratios were calculated at 137 noise measurement points. In addition, we were able to compute the numerical transfer functions from soil columns defined by geotechnical characteristics inside the studied region. A comparison of the results obtained by the experimental and numerical methods showed that the fundamental frequencies are in good agreement, but that the amplitudes obtained by the two techniques are sometimes different. The analysis of H/V spectral ratios enabled us to establish maps to characterize the region: a resonance frequency map and maps of amplification levels as a function of frequency range, leading to a seismic microzonation for the whole of the region.     

采样过程和模数转换对记录的影响及“真实地面运动”获取——地震学上用的数字信号处理的基本原理和实例(讲座3)

通过采样过程和模数转换对记录影响的分析,讨论了数字地震仪记录的动态范围,以及如何使用谱分析方法去除仪器对最终记录的影响,以便获取“真实地面运动”的近似。     

中国数字地震台网数据管理中心日常工作软件的升级和应用

文中阐述了中国数字地震台网数据管理中心（ＣＤＳＮ ＤＭＣ）日常工作软件的升级和升级后新软件的主要功能,并结合新软件的主要命令及运行实例,对升级后软件的实际应用作了简要叙述。     

航磁ΔT解析信号确定线性构造隐伏形态的算法及阿尔金的应用

本文研究了模拟线性地质构造具有普遍意义的有限延深薄板状体ΔＴ的解析信号强度与其几何参数之间的超定方程关系,运用奇异值分解和广义逆技术求解超定方程,获得了高精度的理论反演方法,同时给出了定性解释板状体产状的辅助方法。对阿尔金地区隐伏断裂形态的反演结果,为西藏地体的“北推东移”提供了定量化的地球物理解释证据。文章还勾画了阿尔金与塔里木的深部界线。     

TFe/TiO_2比值在攀枝花层状辉长岩体钒钛磁铁矿矿床勘探中的应用

攀枝花钒钛磁铁矿床是我国特大型晚期岩浆分凝型矿床。本文首次用ＴＦｅ／ＴｉＯ２比值对矿带、矿层、火成堆积旋回进行了详细划分,同时对断层位置、性质及矿床成因进行了判定,并提出在层状辉长岩体中,当ＴＦｅ／ＴｉＯ２比值小于２∶１的部位是寻找独立钛铁矿矿床最佳地段     

Flow of groundwater with variable density and viscosity, Atikokan Research Area, Canada

 Flow of groundwater with variable density and viscosity was simulated at the Atikokan Research Area (ARA) in northwestern Ontario, Canada. An empirical viscosity–concentration equation was modified to include total-dissolved-solids (TDS) data from the ARA. The resulting equation was used successfully to estimate reasonably accurate viscosity values over the expected range of temperature and concentration, in comparison with experimental values derived for sodium chloride solutions. A three-dimensional finite-element code, MOTIF, developed by Atomic Energy of Canada Limited, was used in the simulations. The inclusion of the effects of depth-increasing temperature and TDS-dependent fluid-density distribution, while maintaining only a temperature-dependent viscosity relationship in a simulation, resulted in a more penetrative flow against expected buoyancy effects (i.e., the physics of the system was not honored). Accounting for concentration in the viscosity equation caused water to be less penetrative and more in accordance with the expected physics of the system. A conclusion is that fluid concentration should be considered simultaneously in calculating the density and viscosity of a fluid during modeling of variable-density flow in areas underlain by fluids with high TDS. Results of simulations suggest that both flow directions and magnitudes should be employed simultaneously during the calibration of a model. Large-scale groundwater movement in the ARA may be analyzed with carefully selected vertical no-flow boundaries. By incorporating the geothermal temperature gradient, groundwater recharge increases by 12%; thus, this gradient plays a significant role in groundwater flow at the ARA. Variability in the fluid concentration at the ARA neither decreases nor increases recharge into the groundwater system. The hypothesis that an isolated continuous regional flow system may exist at depth in the ARA is not supported by these simulations. Received, September 1996 Revised, September 1997, February 1998 Accepted, February 1998