可控源音频大地电磁法在地下水勘查中的应用研究

根据可控源音频大地电磁（ＣＳＡＭＴ）法进行地下水勘查时取得的大量资料，通过总结、分析与研究，提出了在蓄水构造的断层上，ＣＳＡＭＴ测量的视电阻车断面等值线图呈中间低、两侧高的异常特征．利用这一模式解决了在山区、半山区，很多地球物理方法难以解决的地下水勘查问题．经打井验证，成井率很高．     

GUIDED LOW-FREQUENCY NOISE FROM AIRGUN SOURCES*

The presence of the water layer in marine seismic prospecting provides an effective waveguide for acoustic energy trapped between the sea-bed and the sea-surface. This energy persists to large ranges and can be the dominant early feature on far-offset traces. On airgun records, there is commonly a lower frequency set of arrivals following the water-trapped waves. These arrivals are not as obvious with higher frequency watergun sources. By using a combination of intercept-time/slowness (τ—p) mapping on observational data and theoretical modelling, we are able to identify the origin of the events. If a very rapid increase in a seismic wavespeed occurs beneath the sea-bed sediments, a new waveguide is formed bounded by the sea surface and this transition zone. The low frequency waves are principally guided within this thicker waveguide. Numerical filtering in the τ—p domain followed by trace reconstruction is very effective in removing the low frequency noise.     

A convenient,one-hand-operated field burette

A simple, cheap and easily constructable burette, particularly useful for alkalinity, dissolved oxygen and hardness titration is described. Precise titrant delivery (<1 μl) is controlled by a handy ‘clothespin valve’ connected to the lower opening of appropriately sized graduated pipettes or burette tubes. The burette is small, flexible and easily portable and should be highly recommended as an all round field burette for limnochemists.     

时空阵列混场源电磁法理论及模拟研究

针对电磁勘探中的混场源输入条件,提出了一种时空阵列混场源电磁勘探方法.假设输入端同时包含天然电磁场源和可控人工场源,输出端进行多站同步观测;基于多输入-多输出系统的分析方法,推导了混场源条件下的时空阵列方程组.提出了系统响应的求解策略,一次性获得所有同步测道对各个场源独立激励时的响应,并分别求取了大地电磁法及可控源电磁法的各种解释参数.在此理论基础上,设计了针对性的施工方案;可控人工场源的选择形式多样,其类型、数量、激励方式及布设位置等不受限制,所有场源的激励可同时进行,无需分步;测区内各测站的布设方式灵活,可根据需要布设单分量测道或多分量测道;同时在测区外布设张量远参考站.利用数值模拟方法,论证了方法的有效性,并与常规方法进行了对比.结果表明,本方法不仅可提高人工场响应的处理精度,还具有一次野外数据采集,可同时获得天然场及人工场电磁响应结果的突出特点,进而提高采集效率,压制噪声影响;本方法集合了天然场源电磁法和人工场源电磁法的优点,为实现不同类型频率域电磁测深方法数据的统一处理提供了思路.     

采用综合物探法进行大坝面板脱空无损探测

面板堆石坝大坝面板脱空无损探测目前仍是一个难题,尚未见到较为成功的探测报道,采用的单一物探方法的探测成果准确率又偏低.因此,如何提高探测准确率是面板脱空无损探测的研究重点.本文通过天生桥一级水电站面板脱空探测的实例,介绍采用综合物探方法进行大坝脱空探测是可行的,并在实践中获得成功,取得了较好的经济效益.     

SOME APPLICATIONS OF IP-TECHNIQUE FOR DIFFERENT GEOPHYSICAL PROSPECTING PURPOSES *

The usefulness of IP-technique for different geophysical purposes is discussed on the basis of field examples. IP and resistivity results are not always correlated, and the IP-information may be unique in prospecting for very low grade sulphide mineralizations. The IP-technique seems to be useful sometimes in prospecting for disseminated Ni-Cu- mineralizations. A massive sulphide mineralization could be localized using IP. The disturbances from different kinds of geological objects other than prospecting targets generally are smaller in IP-work than in resistivity work. It was possible to discriminate between apparent resistivity anomalies caused by shear zones and by sulphide mineralizations by means of IP-measurements. The influence of magnetite on IP- measurements is briefly discussed. The relation between ground magnetic measurements ΔZ and the IP-parameter is in many areas weak and does not seriously influence the interpretation of the IP-measurements. A high correlation between ΔZ and IP-measurements has been found on a titaniferous iron ore. This ore body gives strong IP-anomalies indicating that it is a good IP-target. Finally, the application of small moving arrays in very detailed IP-measurements is found useful for detailed mapping of a mineralized zone under a thin overburden and for determination of the dip of mineralized zones.     

The Acquisition Technique of High-resolution Seismic Data for the Prospecting of Active Faults

The high-resolution shallow seismic technique can be used for more accurately prospecting the position and property of faults and for the preliminary study of fault activity.The author obtains many high quality stack time sections through the prospecting methods of different seismic sources,different group intervals and different observation systems on the Xiadian fault.These sections clearly display the stratum structure and the structure characteristics from several meters to several hundred meters of the...     

21世纪重力与磁法勘探的展望

对21世纪重力与磁法勘探的仪器，数据处理技术，解释理论与方法，应用领域等方面的发展方向进行了分析与展望，发展航空标量，矢量，梯度重力测量和航空全梯度磁力测量，三分量磁力测量，提高综合信息采集能力；开展卫星重磁测量，综合卫星，航空，地面重磁测量资料研究地球结构与构造；发展高精度数据处理技术；重磁异常弱信号的提取，不同深度重磁异常的划分，低纬底变倾角化磁极以及位场面延拓；发展复杂条件下三维重磁场多参数综合反演可视化技术以及快速自动反演技术；探索磁性多参数的应用新领域，充分发挥磁法在环境污染调查中的作用并开拓应用新领域。     

DETERMINATION OF ELECTRICAL PROPERTIES OF THE GROUND AT SHALLOW DEPTH WITH AN ELECTROSTATIC QUADRUPOLE: FIELD TRIALS ON ARCHAEOLOGICAL SITES1

Knowledge of both the electrical resistivity ρ and the dielectric permittivity ? of the ground is important for the determination of characteristics such as granularity, porosity, moisture and salt content. Whereas the measurement of ρ is very common and can be achieved using either the d.c. resistivity method or a wide variety of EM devices, ? remains practically unknown in the low-frequency domain between the IP domain and the high-frequency domain. Following the principle of the quadrupole technique used in d.c. prospecting and of the quadrupolar probe for measuring the complex permittivity of the ionosphere, we propose a new approach which does not require any galvanic contact between the poles and the ground. The transfer impedance can be evaluated using the quasi-static approximation for low frequency or the full EM theory for higher frequencies. The conditions under which both calculations apply are discussed. At low frequencies and for low resistivity ground, the electrostatic quadrupole measures ρ exactly as with the d.c. technique; for higher resistivities or frequencies the simultaneous measurement of both properties becomes possible. Examples in archaeological prospecting are presented and checked against independent d.c. resistivity measurements or excavation analyses.     

TECHNIQUE DE MESURE ET D'INTERPRETATION MINIMISANT LES ERREURS DE MESURES EN MICROGRAVIMETRIE*

Different sources of error influence gavity surveys, particularly shallow “micrograuity” sur-veys. Experiments show that. the most frequent source of error in gravimetric prospecting is bad estimation of drift. Better control of drift exists with the field procedure and interpretation technique developed by the authors, as can be shown theoretically as well as experimentally. The method implies a random or semi-random spatial sequence of measurement points. A real case of field prospecting is described.     

辽宁省义县大铁厂地区金钼矿地质特征与找矿标志

辽宁省义县大铁厂地区金钼矿床为浅成中一高温热液石英脉型,受韧性剪切构造和岩浆活动控制,本文在详细研究了矿床地质及地球物理化学特征基础上,总结了该矿床的主要控矿因素并归纳了主要找矿标志,为进一步在该区找矿指明了方向。     

Signal detectability of marine electromagnetic methods in the exploration of resistive targets

We compare selected marine electromagnetic methods for sensitivity to the presence of relatively thin resistive targets (e.g., hydrocarbons, gas hydrates, fresh groundwater, etc.). The study includes the conventional controlled‐source electromagnetic method, the recently introduced transient electromagnetic prospecting with vertical electric lines method, and the novel marine circular electric dipole method, which is still in the stage of theoretical development. The comparison is based on general physical considerations, analytical (mainly asymptotic) analysis, and rigorous one‐dimensional and multidimensional forward modelling. It is shown that transient electromagnetic prospecting with vertical electric lines and marine circular electric dipole methods represent an alternative to the conventional controlled‐source electromagnetic method at shallow sea, where the latter becomes less efficient due to the air‐wave phenomenon. Since both former methods are essentially short‐offset time‐domain techniques, they exhibit a much better lateral resolution than the controlled‐source electromagnetic method in both shallow sea and deep sea. The greatest shortcoming of the transient electromagnetic prospecting with vertical electric lines and marine circular electric dipole methods comes from the difficulties in accurately assembling the transmitter antenna within the marine environment. This makes these methods significantly less practical than the controlled‐source electromagnetic method. Consequently, the controlled‐source electromagnetic method remains the leading marine electromagnetic technique in the exploration of large resistive targets in deep sea. However, exploring laterally small targets in deep sea and both small and large targets in shallow sea might require the use of the less practical transient electromagnetic prospecting with vertical electric lines and/or marine circular electric dipole method as a desirable alternative to the controlled‐source electromagnetic method.     

THE USE OF VERTICAL LINE SOURCES IN ELECTRICAL PROSPECTING FOR HYDROCARBON*

Conventional electrical prospecting can be extended to the search for deep-seated hydrocarbon deposits, by using the steel casings of drill-holes as vertical line sources. These sources produce at depth a density of current higher than the density created by point sources located at the ground surface. Several tests have shown that the contrast of conductivity between resistive hydrocarbon deposits and the surrounding salt water produces relevant anomalies on a resistivity map obtained with vertical line sources, especially where there exists a superficial masking effect caused by a highly resistive layer. In a survey carried out in the USSR, combined measurements were performed, both with line source and with surface point sources. The detected residual resistivity anomaly roughly delineates the contours of the known hydrocarbon deposit.     

测井和地震联合评价技术在油藏工程中的作用

地球物理测井和地震勘探联合评价油气藏是油气田开发中非常重要的工作.只有借助测井和地震信息才能比较合理地描述非均匀油气藏.在油气藏描述中,孔隙度φ、渗透率x和饱和度S_n是建立油藏物理模型的基础,而这三个参数的空间变化可以借助于测井和地震联合评价技术合理地获取.     

Earthquake dynamics on circular faults: a review 1970–2015

We review the development of earthquake dynamics taken from the point of view of the origin of seismic radiation instead of the detailed study of rupture propagation on complex surfaces. Many features of seismic radiation can be explained by simple models that serve as elementary canonical problems. Some of these properties are very well known like the fact that at low frequencies, the seismic spectrum is proportional to the seismic moment. At high frequencies, on the other hand, radiation is generated by the motion of the rupture front, in particular stopping phases and geometrical obstacles (barriers). A rupture front moving at constant speed does not produce far-field radiation. For many practical applications, for determining source size and stress drop, for example, it is not necessary to determine geometrical details of the rupture. For such cases, a simple circular crack model is quite sufficient. An improvement on this method is to do dynamic inversion on simple, elliptical-shaped sources and letting the rupture start arbitrarily from a point on the fault. This problem can be solved nowadays with finite differences and a variety of inversion techniques.     

Trapping Ionic Mercury Using Different Adsorbents

Of recent, adsorption process has gained a lot of attention as a cheap and effective means of removing trace metals from wastewater prior to discharge into water bodies. Being flexible in design and operation, the process has enabled an optimal recovery of trace metals such that the treated effluents meet the desired standards for waste disposal. Mercury is a toxicant released into the environment from natural and anthropogenic sources. It is notorious for having an unusual tendency to bio‐accumulate and persist in the food chain. Presence of mercury in food, especially those of aquatic sources has drastic implications on human health. Therefore, efforts have been made to develop and optimize low‐cost activated carbon (AC) as adsorbents for scavenging mercury from aqueous effluents. Herein, how mercury accumulates across the food chain, its health implications, and the recent advancement in the use of low‐cost ACs as adsorbent for trapping mercury from wastewater are highlighted. Relationship between the mercury removal efficiency and the surface morphology of the adsorbents as well as the influence of prevailing experimental condition on the sorption process were addressed. Challenges and future prospects of the use of low‐cost adsorbents in addressing mercury pollution in the environment are discussed.     

浙江省妙西多金属矿床成矿模型及找矿标志

笔者通过大量地质、地球化学、球物理和矿床（点）资料研究,提出浙江省妙西多金属矿床成矿模型,该模型正在为普查项目所证实。妙西多金属矿矿床是典型的岩浆期后热液矿床,矿体主要受本区的三级构造即岩体接触带构造和地层不连续界面构造控制。地球物理测量提供的深部信息和地质构造标志是本区多金属矿直接找矿标志,地表物化探资料在普查工作中可以起辅助作用。     

Hydrogeological investigation of porous environments by radio magnetotelluric-resistivity (RMT-R 12–240 kHz)

This paper presents a methodology in geophysics applied to the study of porous aquifers. This methodology is based on an improved “very low frequency-resistivity” equipment, on greater importance being attached to the local geological heterogeneity of the environment, and also on a method of data processing which is simple but well adapted to a large number of studies concerning prospecting, protection and management of underground water.The radio magnetotelluric-resistivity equipment (RMT-R) is derived from the classical VLF-resistivity equipment. Its increased reception band (12–240 kHz) allows us to realize rapid frequency soundings.In the example to be discussed, a geostatistical analysis of semivariance, made on a series of more than 600 measurements, shows a spatially structured geophysical heterogeneity, both for the values of resistivity and for those of phase. The correlation between this geophysical heterogeneity and the lithological heterogeneity of the environment is confirmed by mechanical soundings (geological test holes). The indirect relations between this geophysical heterogeneity and the hydraulic behaviour of the aquifer system can be estimated and are confirmed, on this specific site, by the observation of the piezometric levels.The results of our study illustrate the positive contribution RMT-R can make to hydrogeology. Above all they show that those porous environments, frequently considered as homogeneous, cannot be considered as such either hydrogeologically or geophysically.     

Ricker子波核最小二乘支持向量机在地震勘探信号去噪应用中的参数设置研究

最小二乘支持向量机（LS-SVM）用于拟合回归处理时的参数设置一直是一个难题,它会受到信号类型和强度、核函数类型、噪声强度、计算精度要求等因素的影响.本文针对Ricker子波核LS-SVM去除地震勘探信号中随机噪声问题,讨论和分析了向量机参数、核参数对去噪性能的影响.实验表明,核参数f可取为地震记录的主频,不能较准确估计时宁大勿小;向量机参数γ只要不取得过小,一般情况下都是能接受的.采用此方法对含不同强度噪声的地震勘探信号进行了去噪处理.     

Cancelling directional EM noise in magnetoteilurics1

The prospecting of densely urbanized areas by the measurement of magnetic and electric natural fields is severely hampered by electromagnetic (EM) noise. Active man-made EM noise sources can generally be considered fixed in space, thus affecting the magnetotelluric (MT) signals of a measuring site mainly along their polarization directions. Taking advantage of the impulsive nature of polarized EM noise, a time-domain directional noise cancelling (DNC) technique is proposed. The comparison of noisy data with data predicted, using a low noise reference signal or with data interpolated whenever no reference is available, allows the detection of the most likely noise sources with prevailing directional patterns using a Bayes's criterion. The DNC approach is general and can be adapted, depending on the reference signal used (single-site or remote-reference). In field data, hodograms of the prediction residuals basically confirm the directional noise model assumed in DNC. An example is presented in which the DNC technique has been applied to a single-site MT survey carried out in northern Italy, where the signal was heavily corrupted by noise with prevailing directional properties due to the densely urbanized area. MT apparent resistivities and phases obtained at the site of the survey before and after DNC are presented and discussed.