考虑渗流场作用下的隧道开挖分析

由于隧道的开挖,破坏了初始地应力场与渗流场。以圆形隧道为例,采用有限差分程序计算考虑渗流场作用时,隧道开挖后洞室周围应力场、孔隙水压力、位移场的分布情况,并对比计算了是否考虑渗流效应时位移场的差异,以及不同水位导致的位移场的不同分布状态。提出了相应的隧道防排水、设计与施工相关建议。     

Variations of the dipole magnetic moment of the sun during the solar activity cycle

Observations of the large-scale solar magnetic field (synoptic maps) and measurements of the magnetic field of the Sun as a star (the total magnetic field) are used to determine the dipole magnetic moment and direction of the dipole field for three successive solar cycles. Both the magnetic moment and its vertical and horizontal components vary regularly during the cycle, but never disappear completely. A wavelet analysis of the total magnetic field shows that the amplitude of the 27-day variations of this field is very closely related to the magnetic moment of the horizontal dipole. The reversal of the global dipole field corresponds to a change in the inclination of its axis and occurs in a series of steps lasting one to two years rather than continuously. Before the onset of the reversal, the dipole axis precesses relative to the solar rotational axis, then shifts in a meridianal plane, reaching very low latitudes, where a substantial shift in longitude then begins. These results are discussed in connection with helioseismological data indicating the existence of oscillations with a period of about 1.3 yr and properties of dynamo processes for the case of an inclined rotator.     

论川西坳陷上三叠统气田水化学场及其分带

在阐述川西坳陷地质构造背景基础上，根据大量水化学测试数据，概括了上三叠统气田水化学成分基本特征，勾划了气田水10个水化学参数化学场图，揭示了气田水化学分布规律性，并划分了正向和斜向垂直水化学分带。对于相关的气田水渗流场和地下水成因的研究具有重要的理论意义。     

The increase in the magnetic flux from the polar regions of the Sun over the last 120 years

The latitudes of the zonal boundaries of the global magnetic field of the Sun are determined from the magnetic neutral lines on synoptic Hα maps obtained during 1878–1999. The area of the polar zone occupied by magnetic field of a single polarity at solar minima has doubled over the last 120 years. This provides an explanation for the secular increase in heliospheric characteristics, which differs from the two-fold increase of the magnetic field strength predicted for this period. The temporal variations of the magnetic flux from the polar regions and their role in global changes of the Earth’s climate are discussed in connection with secular variations in the structure of the internal magnetic field of the Sun.     

确定地下管线深度的方法原理研究

从理论上阐述了利用倾斜磁场最大值点、利用垂直磁场分量峰值点和利用水平磁场分量半极值点确定地下管线深度的原理方法,指出了利用倾斜磁场最大值点确定管线深度时在原理上存在的问题和不实用性,同时从原理上和实用中筛选出了最佳的定深方法-水平磁场分量三角法.     

改进的倾斜角法在位场场源边界识别中的应用

位场场源边界识别是位场数据分析解释中的重点内容之一。相邻异常源由于场的叠加而难以区分,尤其是对于叠加异常中不同深度的场源边界的识别。倾斜角法是位场数据处理中常用的边界增强方法之一,能有效突出低振幅、短波长的异常特征。本文基于倾斜角法定义了新的位场边界探测方法,该方法利用倾斜角方程中位场二阶垂直导数与垂向导数水平导数之比进行计算,能有效区分相邻异常源产生的叠加异常,突出叠加异常中不同深度场源的边界特征。通过综合模型和实测数据,并与现有的基于导数的位场边界探测方法进行比较,评价了该方法的应用效果。结果表明,该方法对场源深度的变化不太敏感,它可以更准确地确定场源边界,区分相邻异常源的叠加异常,尤其对密集型组合地质构造的识别有较好的效果,即使是在场源埋深较大情况下,也能突出叠加异常中不太明显的微弱变化的线性异常特征,以及弱异常源的形态特征,可为精细研究局部地质构造提供技术支持。     

Improving the geoid accuracy by adapting the reference field

In the frame work of the Austrian Geoid 2000 project, the accuracy of the geoid has to be enhanced. One of the possibilities is to use an adapted reference field. The traditional remove/restore technique has the disadvantage of removing a part of the effect of the topography and its compensation twice. In order to avoid this double consideration the effect of the topographic-isostatic masses for the used fixed data window has been subtracted from the reference field yielding an adapted reference field. This adapted reference field has been used for the remove/restore technique. The paper shows a comparison between the geoid computed by the adapted technique using the enhanced reference field, the geoid computed by the traditional remove/restore technique and the geoid based on the RTM-method for the remove/restore process. All the models are checked against a geoid derived by GPS and levelling points. The geoid based on the adapted remove/restore technique shows the best results.     

Impact of the magnetic field on the structure of accretion disks in semi-detached binaries

We discuss characteristic features of the magnetic gas-dynamical structure of the flows in a semi-detached binary system obtained from three-dimensional simulations, assuming that the intrinsic magnetic field of the accreting star is dipolar. The turbulent diffusion of the magnetic field is taken into account. The SS Cyg system is considered as an example. Including the magnetic field can alter the basic parameters of the accretion disk, such as the accretion rate and the characteristic density. The magnetic field in the disk is primarily toroidal.     

Over how much time should the geomagnetic field be averaged to obtain the mean-palaeomagnetic field?

Average geomagnetic field models are now available over six orders of magnitude in time. Models based on Present and historical, archaeomagnetic and palaeomagnetic data illustrate how the amplitudes of secular variation of nonaxial dipole terms strongly decrease as a function of averaging window, mostly when jumping from the 1-yr to the 1700-yr average. The mean archaeomagnetic field bridges the gap between the complex historical field and the far simpler palaeomagnetic field, and appears to be much closer to the latter. Confidences in average field coefficients based on statistical field models give a quantitative basis to the practice of averaging data over a few millenia in order to 'suppress secular variation'. In particular, the axial quadrupole emerges from noise when the available time series exceed about 6 kyr. This happens to be close to the timescales of excursions and reversals. It is now a priority to obtain detailed data spanning the last 50 kyr.     

Structural analysis of the gravity field over the American-Antarctic Ridge

This paper discusses the structure of the American-Antarctic Ridge based on analysis of the gravity field. Analysis of the gravity field in different reductions and its transforms allowed the revelation of zonal, regional, and local specific features in the field’s structure and their correlation with contemporary notions on the tectonic zoning of the American-Antarctic Ridge and adjacent regions. The lineament structures of the field allowed locating the areas of spreading zones and principal transform and fracture zones. Comparison between the location of these structural features and the interpretation results of shipboard magnetic measurements confirmed the reliability of the received data. Results of the performed investigations presented in the form of structural schemes are a basis for constructing a model of the tectonosphere under the American-Antarctic Ridge.     

On the efficiency of the indicator approach in geostatistics

A common problem in geostatistics is to determine whether or not the value of a random field at an unsampled location exceeds a specified threshold using observed values of the random field at sampled locations. Under the indicator approach, the only information used to classify the unobserved value is whether or not the observed values exceed the threshold. This note shows that the loss of information from applying the indicator approach may be modest in the case where the underlying random field is Gaussian.     

根据地球物理场特征评价核废物处置场址——对疏勒河断裂带稳定性评价

以疏勒河断裂带中段及其以北的北山地区遥感地质图象特征为基础，从该地区地球物理场（包括磁场、电磁场、射气场和地温场）特征的角度，对建造高放废物处置库的稳定性进行评价，得出结论：疏勒河断裂带中段及其北山地区的地质稳定性较好，是高放废物处置库选址的有利地区。     

高压密封舱与磁场传感器的综合频响变异及其实验验证

大地电磁测深在陆地上的方法技术成熟, 但将其移植到海洋中却遇到了较多的技术问题.其中之一是如何将磁场传感器运抵海底实施测量.为抵御海水的侵蚀和抗衡海下的环境压力, 需要研发装载磁场传感器的密封舱.该舱体需满足测磁的技术要求, 即制造材料的非磁性, 且兼顾海洋作业设备轻便的特点.LC4超硬铝合金在可选的材料中性价比居高, 然而用它制成的高压密封舱并非十分完美.因它的弱磁性, 使得磁场传感器装入舱体后, 整体频率响应发生了部分变异.这种变异虽不影响磁场传感器的使用, 但要对其规律特征予以测定, 方能剔除由此产生的对磁场测量的不良影响.在所构思的实验装置中, 通过人为产生扫频磁场, 对密封和非密封条件下的磁场传感器进行激励.在响应输出端, 测取幅频特性和相频特性, 获得归一化的对比资料和频响异常曲线, 从而对密封前后磁场传感器的性能变化有较清楚的认识.实验结果揭示, 由高压密封舱引起的频响变异发生在中高频区段.实验数据可作为标定资料, 对海底大地电磁探测的实测信号进行校正后, 即可还原出真实的海底场源信息.      

Study on the variations of geomagnetic-field intensity during the quaternary in special reference to thermomagnetic measurements on volcanic rocks

Thermomagnetic measurements have been made on thirteen samples of Quaternary volcanic rocks of different episodes from three localities by Thellier’s method. Paleomagnetic field intensities for the three Quaternary sub-periods have been obtained: 0.62 for Early Pleistocene, 1.01 for Middle Pleistocene and 1.57 for Late Pleistocene with respect to the present magnetic field intensity. The results indicate that the geomagnetic field intensity has been increasing since Pleistocene time, and there exists a close relationship between paleomagnetic field intensity and climatic changes, i.e., the climate trends to become colder with increasing paleomagnetic field intensity, and vice versa.     

地下水循环对围岩温度场的影响及地热资源形成分析——以平顶山矿区为例

地下水循环方式的不同对围岩温度场产生的影响有很大差异。当低温地下水向下运动时 ,将引起围岩温度降低 ,出现低温异常 ,从而阻碍地热资源的形成 ;当深循环的地下水在循环过程中被岩温加热 ,并在一定地质条件下向上循环时 ,将引起流经围岩的局部温度升高 ,在浅部形成局部地热异常 ,进而促进地热资源的形成。因此 ,地下水循环对围岩温度场的影响在一定程度上决定着地热资源的形成。本文在研究地下水循环对围岩温度场的影响基础上 ,利用地球化学地热温标和同位素方法对平顶山矿区地热资源的形成进行了分析 ,预测了该区地温场温度     

东营凹陷地热田特征及成因机理研究

按照三级、四级大地构造单元,凸起、凹陷的界线、构造断裂带、地热异常的范围等,将鲁西北地热区划分为若干地热田;在参考鲁北地区馆陶组、东营组热储埋深、厚度、水化学类型、水量、水温等基础上,结合当地的地热规划、开发利用情况及行政区界等,将东营凹陷地热田进一步划分为5个地热区块;通过对东营凹陷地热田已有钻探资料和区域地热地质资料的研究,结合勘查项目研究成果,分析了地热田的埋藏条件、补径排条件、地温场及水文地球化学特征,阐述了地热田边界条件以及地热地质特征,东营凹陷地热田蕴藏着丰富的中低温地热资源,热流体为碎屑岩类裂隙孔隙承压水,矿化度较高,主要由周边山区大气降水入渗补给形成,并建立了地热田成因机理概念模型,为地热资源的合理开发利用提供了重要依据。     

不规则回线源层状介质瞬变电磁场正反演研究及应用

不规则回线内任一点的电磁场可以看成是其内部多个圆形回线在该点的电磁场之和,因此,只要求出不规则回线内各个圆形回线在该点的电磁场,将它们叠加就可得出不规则回线在该点的电磁场。此种方法的关键是如何在不规则回线内划分圆形回线。采用的方法是首先在不规则回线内以测点为圆心做一个圆,这时整个回线被分为圆内和圆外两部分;然后再将回线内圆外的部分划成众多的小圆形,此时就将求解不规则回线的电磁场转化为求解圆形回线的电磁场。     

鄂尔多斯盆地上古生界两大气田不同石英砂岩储层 特征对比研究

通过对鄂尔多斯盆地上古生界榆林气田和苏里格气田石英砂岩储层特征的对比,指出榆林气田山2段石英砂岩储层属于相对低孔高渗型储层,苏里格气田盒8段石英砂岩储层属于相对高孔低渗型储层;通过分析两类石英砂岩的物源、沉积条件和成岩作用等因素,认为沉积期海水改造及后期成岩作用形成了榆林气田山2段储层的低孔高渗,而沉积时的高杂基含量与后期成岩共同作用形成了苏里格气田盒8段储层的高孔低渗。     

Experimental Verification and Research for the Distortion in the Integrated Frequency Responses of the High-Pressure Sealed Cabin and Magnetic Field Sensor

Although magnetotelluric sounding method applied to the land is advanced, there are many difficulties when it is applied to marine environment, one of which is how to lay magnetic field sensors down to the seafloor to complete measurements. To protect the magnetic field sensors from intense erosion and high pressure, suitable high-pressure sealed cabins must be designed to load them. For the consideration of magnetic measurement and marine operation, the sealed pressure cabin should be nonmagnetic and transportable. Among all optional materials, LC4 super-hard aluminum alloy has the highest performance of price/quality ratio to make the sealed pressure cabin. However, it does not mean that the high-pressure sealed cabin made using LC4 will be perfect in performance. In fact, because of its weak magnetism, the pressure cabin made using LC4 has distorting effect on frequency responses of the magnetic field sensors sealed in it. This distorting effect does not affect the use of the magnetic field sensor, but if we want to eliminate its effect, we should study it by experimental measurements. In our experiment tests, frequency sweep magnetic field as excitation signal was used, and then responses of the magnetic field sensor before and after being loaded into the high-pressure sealed cabin were measured. Finally, normalized abnormal curves for the frequency responses were obtained, through which we could show how the high-pressure sealed cabin produces effects on the responses of the magnetic field sensor. Experimental results suggest that the response distortion induced by the sealed pressure cabin appears on mid- andhigh-frequency areas. Using experimental results as standardization data, the frequency responses collected from seafloor magnetotelluric measurements can be corrected to restore real information about the seafloor field source.     

Electron acceleration in the ionosphere of Io

A mechanism for the acceleration of electrons in the ionosphere of Io due to the moon's motion through the Jovian magnetic field and the presence of Io's ionosphere is considered. Attention is drawn to the important role of the anisotropic conductivity of the ionosphere, which results in the formation of a longitudinal (with respect to the planetary magnetic field) component of the charge-separation electric field. Owing to this anisotropy, the electric field induced by the motion of Io, E_i, produces in Io's ionosphere not only a Pedersen electrical current along E_i but also a Hall current that is approximately perpendicular to the moon's surface in the “upstream” and “downstream” parts of the ionosphere. However, this current cannot be closed through the surface, leading to the formation of a powerful charge-separation field in Io's ionosphere. This field has a component parallel to the magnetic field, with an amplitude comparable to that of the induced electric field. Electron runaway along the magnetic field is also considered, and the occurrence of “active longitudes” and preferred locations for the sources of decametric radio emission in the northern hemisphere of Jupiter are interpreted. The characteristic energies and fluxes of the accelerated electrons injected into Io's flux tube are estimated. The energy of these electron fluxes is sufficient to produce the electromagnetic radiation observed from Io's magnetic tube.