A statistical prediction technique for deriving contour maps from geophysical data

A technique for preparing contour maps is presented which has particular applicability for geophysical data. This technique derives from the assumption that each measured value is a sample from a statistical distribution which is taken to be valid in the area around that sample location. This distribution may be specified in the manner which best defines the relationship between the data and its spatial environment. Extending this principle to cover all areas to be mapped, and not just those measured, it is possible to predict values over a grid array of locations and hence to produce a contour map. Inherent in this simple procedure is: (i) the ability to adjust to the nature of the data being contoured; (ii) the elimination of edge effects; (iii) visual indication of the relative accuracy with which contours are located, at all points of the map; (iv) the automatic downgrading of data values which are in error; (v) the ability to contour combinations of measured data values without compounding errors; and (vi) a relatively simple extension to data spatially distributed in three dimensions.Research Council of Alberta Contribution No. 618.     

Relationship between geological,geophysical and geochemical data obtained from blind lead-zinc mineralization at Keban,Turkey

The Keban Pb-Zn deposit is an old and important mine in Turkey, and intensive geological, geophysical exploration and diamond drilling have been carried out in the area in an attempt to find new ore reserves. Graphitic schist in the hanging wall of the ore zone, which has sealed the deposit, has produced many false geophysical anomalies. Thus, it is apparently difficult to distinguish the geophysical anomalies related to ore deposits from those caused by the graphitic schist and other geological features of the area. Geochemical data obtained from soil samples over the deposite show significant leakage anomalies indicating the mineralization at depth. The geochemical data are also helpful in the interpretation of geophysical data.     

A comparison of surface fitting algorithms for geophysical data

Many treatments in geophysics require regular grids of data. Since the data are generally recorded irregularly (e.g. gravity measurements along roads) or even on tracks (e.g. satellite measurements), it is necessary to grid the observed data. We present the result of a comparison of various surface fitting algorithms carried out in order to check their reliability. Two different types of sampling have been verified: (i) clouds of points and (ii) points along tracks. Five algorithms have been extensively tested: (1) polynomial fit, (2) algorithm using a combination of spline-laplace, (3) krigeage (4) least-squares fitting method, and (5) finite element method. The suitability of each method for different sets of data and the limitations (in terms of amplitude and gradient) are discussed.     

A dynamic model of the Hellenic Arc deduced from geophysical data

Combined gravity and seismic data from Greece and the adjacent areas have been used to explain the high seismicity and tectonic activity of this area. Computed 2-D gravity models revealed that below the Aegean region a large “plume” of hot upper-mantle material is rising, causing strong attenuation of the crust. The hot “plume” extends to the base of the lithosphere and has very probably been mobilized through compressional processes that forced the lithosphere to sink into the asthenosphere. The above model is supported by: high heat flow in the Aegean region; low velocity of the compressional waves of 7.7 km/sec for the upper mantle; lower density than normal extending to the base of the lithosphere; teleseismic P-wave travel-time residuals of the order of +2 sec for seismic events recorded at the Greek seismic stations; volcanics in the Aegean area with a chemical composition which can be explained by assuming an assimilation of oceanic crust by the upper mantle; deep seismicity (200 km) which has been interpreted by various authors as a Benioff zone.     

地球物理数据处理中坐标投影计算方法初探

实际生产应用中计算投影时多存在一些问题和误区,本文简要说明了投影及投影距离的计算方法,并列举了生产中常见的两类问题算法,指出其存在的问题。同时编制了相关程序,利用野外实际测点坐标资料进行了较为详细的对比分析。结果表明所用算法在实际应用中更为合理,可以有效指导生产工作。     

The hungarian magnetic network and the processing of the obtained data

In 1994–1995 a geomagnetic survey was carried out on the territory of Hungary and the neighbouring regions on 195 stations. Magnetic declination, inclination and total field were directly observed. Some of the stations were measured jointly with Istituto Nazionale di Geofisica (ING), Roma. The results were reduced to the epoch of 1995.0. Normal fields for the magnetic components were determined as second order functions of the geographic coordinates. The polynomial coefficients have been computed in three different ways: by means of simple and weighted least squares procedure and using the adjustment according to the “most frequent value”. In the present paper the mathematical foundation of these methods and the comparison between the obtained results will be presented.     

Geological structure of central East Antarctica from geophysical data

Examination of the subglacial topography of central East Antarctica reveals the block structure of the Earth’s crust in this region. The intracontinental blocks of the subglacial Vostok Highlands (400 masl), Komsomol’sky Mountains (700 masl), Schmidt Basin (150 masl), and Aurora Basin (?300 masl) are distinguished. The geological nature of the Komsomol’sky Subglacial Mountains (KSM) and the Schmidt Subglacial Basin (SSB) is interpreted from gravity measurements and regional aerogeophysical routes. The basin of Vostok Subglacial Lake (VSL) is located in the conjugation zone of these blocks. The KSM are considered to be a block of the Proterozoic mobile belt disturbed by a system of normal and reverse faults. The SSB is a rigid cratonic block partly overlapped by platform cover. The localization of the VSL Graben in the zone of conjugation of heterogeneous blocks testifies to its formation in a deep fault zone characterized by intense normal and reverse dislocations.     

Deep tectonic subdivision of Kazakhstan,from geophysical data

Interpretative analysis of geological-geophysical data, with a comprehensive characterization of the principal tectonic blocks of Kazakhstan (fig. 3) and the map of abyssal fractures, from the “M” surface up, each with its own orientation, dip, and the accompanying specific complex of intrusive rocks (fig. 4), lead to the map of tectonic regions of the country (fig. 5) – an intricate configuration of discrete and/or presumptive structures of different origin, age, position, stage and other characteristics controlled essentially by some particular zone of abyssal fractures. – IGR Staff.     

地球物理数据处理技术中的图形与感兴趣区编辑技术的研究与实现

图形编辑与感兴趣区编辑在地球物理数据处理中应用越来越广泛。这里借鉴CAD中图形编辑的功能,研究与实现了地球物理数据处理中人机交互图形编辑的基本功能。在图形编辑的基础上,进行了图形所对应图像的属性编辑,进而实现了在遥感数据处理中感兴趣区编辑的基本功能。     

二维EMD方法在物化探数据处理中的应用研究——以云南个旧地区为例

文章采用二维EMD方法对云南个旧地区物化探数据进行非线性的多尺度分析与分解,有效分离了物化探异常,揭示深层次找矿信息.证明了二维EMD分解得到的所有分量都具有实际地质意义,它将是一种新的物化探数据处理方法.     

Web-Based interrogation of large-scale geophysical data sets from handheld devices

This paper describes the issues related to using handheld devices to interrogate wirelessly large-scale geophysical data over the Web using a client–server configuration. A modification of our current Web-based data interrogation program addresses specifically the limitations of current handheld devices with wireless access, such as processor speed, screen size and resolution, memory, and network speeds. The system uses a combination of Java, Python, and C in order to run remotely from the handheld device, while incorporating the power and memory capacity of a large workstation server.     

Deep structure of Anadyr' oil-gas basin,from geophysical data

Positions of the Senonian-Danian complex, in which economic accumulations of hydrocarbons may be expected, are defined; its structural isopachs are determined (fig. 1), and several local uplifts are identified in the basin, as targets for further exploration. -- V.P. Sokoloff.     

A method for stratigraphic correlation of several boreholes

The borehole slotting method previously proposed by Gordon and Reyment for two boreholes may be extended to three or more boreholes, but soon becomes computationally intractable. We propose another method based on the mixture model of cluster analysis, the computational labor of which increases linearly with the number of boreholes. This method produces profiles of the unknown strata to which the individual boreholes are easily matched by the two-borehole slotting method.     

曙光雷达数据处理软件系统

针对岩土工程探测对象的隐蔽性与复杂性,开发了曙光雷达数据处理软件系统,实现了不同类型雷达数据的共享数据处理、分形处理、偏移、联合反演、小波变换等功能;现场验证及试用结果表明,该软件系统可以改善地下目的物探测的分辨率和真实度,可为岩土工程施工提供较准确的地下障碍物资料。     

Self-organizing maps for geoscientific data analysis: geological interpretation of multidimensional geophysical data

Data interpretation is a common task in geoscientific disciplines. Interpretation difficulties occur especially if the data that have to be interpreted are of arbitrary dimension. This paper describes the application of a statistical method, called self-organizing mapping (SOM), to interpret multidimensional, non-linear, and highly noised geophysical data for purposes of geological prediction. The underlying theory is explained, and the method is applied to a six-dimensional seismic data set. Results of SOM classifications can be represented as two-dimensional images, called feature maps. Feature maps illustrate the complexity and demonstrate interrelations between single features or clusters of the complete feature space. SOM images can be visually described and easily interpreted. The advantage is that the SOM method considers interdependencies between all geophysical features at each instance. An application example of an automated geological interpretation based on the geophysical data is shown.     

Comments on “a statistical prediction technique for deriving contour maps from geophysical data”

Mathematical Geosciences -