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  • Articles  (28)
  • cluster analysis  (14)
  • sampling
  • structure
  • 2000-2004  (4)
  • 1970-1974  (24)
  • Geosciences  (28)
  • Architecture, Civil Engineering, Surveying  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Oceanic ridge off-axis deep structure in the Mansah region (Sumail massif, Oman ophiolite) (2000)
    Springer
    Marine geophysical researches 21 (2000), S. 243-257 
    Details
    ISSN: 1573-0581
    Keywords: diapir ; mantle ; Oman ; ophiolite ; seamount ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Large scale structural mapping of the Oman ophiolite indicates that the Mansah area (Sumail massif) was a ridge off-axis region at the time the ophiolite was detached. This paper presents a detailed structural mapping of the region. We show that, as opposed to other off-axis areas, it contains plunging lineations, correlated with a thick Moho transition zone and chromite pods, indicative of a mantle diapir. However this diapir has a discontinuous structure, it is bounded by shear zones and types of diabases that are not found elsewhere in Oman; it also has a broken crust, strongly affected by hydrothermal alteration. This suggests that Mansah fossilized an off-axis diapir intruding a cooling lithosphere. It may be a good candidate to be the root of an off-axis seamount such as those found in the East Pacific, and may bring new insights into this particular volcanism which we are only beginning to explore.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026741208295
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  • 2
    Electronic Resource
    Electronic Resource
    Refined Locations of The Swarm Earthquakes In The Nový Kostel Focal Zone and Spatial Distribution of The January 1997 Swarm In Western Bohemia, Czech Republic (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 210-226 
    Details
    ISSN: 1573-1626
    Keywords: earthquake swarms ; cluster of foci ; relative location ; cluster analysis ; multiplet events
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract In order to improve the accuracy of the spatial distribution of earthquake foci in the principal Novy Kostel focal zone, refined focal locations of about 1500 micro-earthquakes of the 1991 – 1997 period were determined using the relative Master-Event location method. To estimate the reduction in the scatter of located hypocentres, the results were compared with those obtained by routinely used FASTHYPO method and cluster analysis (the nearest-neighbour method) was applied to the located foci to evaluate the spatial distribution of the foci. Based on the results of refined location and of the cluster analysis, a concept of seismic energy release in space and time in the main focal zone was developed. Especially the January 1997 earthquake swarm was studied in detail: 946 events were located with the Master-Event location method, and the dimensions and geometry of focal clusters were determined. Type analysis was applied to waveforms to divide approximately 800 located events into eight multiplet groups to each of which a characteristic source mechanism was assigned. The spatial distribution of the foci as well as of the eight types of source mechanisms was revealed in this way and also the planes fitting the clusters of foci with two predominant source mechanisms were determined fairly well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022162826079
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  • 3
    Electronic Resource
    Electronic Resource
    Statistical considerations for grain-size analyses of tills (1971)
    Springer
    Mathematical geology 3 (1971), S. 227-238 
    Details
    ISSN: 1573-8868
    Keywords: classification ; data processing ; graphics ; mapping ; mathematics ; plotting ; sampling ; statistics ; sedimentology ; stratigraphy ; grain-size analysis ; textural analysis ; glacial geology ; Pleistocene stratigraphy ; till
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Relative percentages of sand, silt, and clay from samples of the same till unit are not identical because of different lithologies in the source areas, sorting in transport, random variation, and experimental error. Random variation and experimental error can be isolated from the other two as follows. For each particle-size class of each till unit, a standard population is determined by using a normally distributed, representative group of data. New measurements are compared with the standard population and, if they compare satisfactorily, the experimental error is not significant and random variation is within the expected range for the population. The outcome of the comparison depends on numerical criteria derived from a graphical method rather than on a more commonly used one-way analysis of variance with two treatments. If the number of samples and the standard deviation of the standard population are substituted in at-test equation, a family of hyperbolas is generated, each of which corresponds to a specific number of subsamples taken from each new sample. The axes of the graphs of the hyperbolas are the standard deviation of new measurements (horizontal axis) and the difference between the means of the new measurements and the standard population (vertical axis). The area between the two branches of each hyperbola corresponds to a satisfactory comparison between the new measurements and the standard population. Measurements from a new sample can be tested by plotting their standard deviation vs. difference in means on axes containing a hyperbola corresponding to the specific number of subsamples used. If the point lies between the branches of the hyperbola, the measurements are considered reliable. But if the point lies outside this region, the measurements are repeated. Because the critical segment of the hyperbola is approximately a straight line parallel to the horizontal axis, the test is simplified to a comparison between the means of the standard population and the means of the subsample. The minimum number of subsamples required to prove significant variation between samples caused by different lithologies in the source areas and sorting in transport can be determined directly from the graphical method. The minimum number of subsamples required is the maximum number to be run for economy of effort.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02045793
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  • 4
    Electronic Resource
    Electronic Resource
    Statistical analysis of tectonic patterns in areal volcanism: The bunyaruguru volcanic field in West Uganda (1971)
    Springer
    Mathematical geology 3 (1971), S. 335-355 
    Details
    ISSN: 1573-8868
    Keywords: nearest neighbor analysis ; regression analysis ; statistics ; trend analysis ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A quantitative analysis was made of the spatial arrangement of 149explosion craters in the western rift of Uganda. A variety of methods demonstrate that the spatial pattern of the craters reveals significant structural patterns that have guided volcanism to the surface. It is shown that the east-west elements in the field affected location, and the main rift fault is resolved into two main components. Tentatively, a possible dextral transform fault is identified that affected the relative location of the two main zones of activity. Grouping techniques demonstrate that crater groups obey an exponential rank-size rule and allow a mapping of the craters into energy classes that reveals a concentric pattern of energy in the field. The effect of the topography on energy levels and crater size show that only topography greater than 11,000ft could have prevented all eruptive activity, but the smaller energies and craters are sensitive to height differences on the order of the height of the rift wall, about 1000ft. Total energy in each crater class size is roughly constant, and the field energy could create one or two single craters comparable in size to small central volcanoes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02083356
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  • 5
    Electronic Resource
    Electronic Resource
    Numerical classification applied to certain Jamaican eocene nummulitids (1971)
    Springer
    Mathematical geology 3 (1971), S. 297-311 
    Details
    ISSN: 1573-8868
    Keywords: classification ; cluster analysis ; discriminant analysis ; numerical taxonomy ; paleontology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Eighty-eight specimens of Eocene nummulitids from the Yellow Limestone Formation of northwestern Jamaica are classified according to quantitative measurements of morphologic parameters that are generally considered to be taxonomically useful. The specimens are grouped into homogeneous classes by the computer screening of differently oriented data projections. By this method, the use of similarity coefficients and the question of a priori weighting of characters, for which numerical taxonomy has been heavily criticized, are both avoided. The stability of the classes thus obtained is validated by discriminant analysis. These techniques provide an objective view of phenetic differences among specimens and show how the measured characters produce those differences. Tightness of coiling and total number of whorls, prove to be the most useful features in discriminating between groups but seem to have taxonomic value only at the specific and not at the generic level. This suggests that the generaOperculinoides andNummulites are synonymous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02045797
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  • 6
    Electronic Resource
    Electronic Resource
    Computer program to analyze directional data, based on the methods of Fisher and Watson (1972)
    Springer
    Mathematical geology 4 (1972), S. 177-202 
    Details
    ISSN: 1573-8868
    Keywords: cluster analysis ; factor analysis ; mapping ; statistics ; petrology ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Based on the methods of Fisher and Watson,Fortran iv computer programs are presented for the following analyses of directional observations on the sphere: (1) to determine if points are randomly distributed; (2) to estimate the azimuth and inclination of the center (mean direction) of a cluster and to estimate the precision (closeness) with which points are clustered; (3) to determine if two or more clusters have the same mean direction; (4) to determine if two clusters have the same precision of clustering; and (5) to locate the pole of a greatcircle girdle of points. Limitations of these analyses for undirected directional observations on the hemisphere also are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02311717
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  • 7
    Electronic Resource
    Electronic Resource
    Counting error in petrographic point-count analysis: A theoretical and experimental study (1971)
    Springer
    Mathematical geology 3 (1971), S. 15-41 
    Details
    ISSN: 1573-8868
    Keywords: modal analysis ; sampling ; statistics ; mineralogy ; petrology ; sedimentology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The binomial model, commonly used to estimate counting error in point-count analysis, misestimates this error when the observation points on a grid are positively or negatively correlated. A model, called the “cell model,” is proposed as an alternative to the binomial model for use in studies, especially with coarse-grained rocks, in which such correlation is known or thought to exist. In the new model the thin section is conceptually partitioned into a number of cells (six is recommended), and the assumption is made that the proportions in the individual cells are statistically independent and that their variance does not differ from cell to cell. Empirical relations obtained from a suite of 200 thin sections of limestones are in reasonable support of the prediction that large particle size adversely affects counting error estimates based on the binomial model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02047430
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  • 8
    Electronic Resource
    Electronic Resource
    Numeric examination of multivariate soil samples (1971)
    Springer
    Mathematical geology 3 (1971), S. 1-14 
    Details
    ISSN: 1573-8868
    Keywords: classification ; cluster analysis ; principal components analysis ; numerical taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Numerical methods for the examination of multivariate soil samples are presented in geometric terms. Techniques of coordinate representation by principal components, by nonmetric scaling, and by a new method are discussed, as are techniques for agglomerative hierarchic cluster analysis. These are illustrated by two sets of previously published data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02047429
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  • 9
    Electronic Resource
    Electronic Resource
    Deciphering Groundwater Flow Systems in Oasis Valley, Nevada, Using Trace Element Chemistry, Multivariate Statistics, and Geographical Information System (2000)
    Springer
    Mathematical geology 32 (2000), S. 943-968 
    Details
    ISSN: 1573-8868
    Keywords: principal components analysis ; cluster analysis ; population partitioning ; trace element compositions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The origin of groundwater discharging via evapotranspiration and from springs within Oasis Valley, Nevada, is of concern owing to the close proximity of the Nevada Test Site (NTS) and the possible contamination of groundwater as a result of underground nuclear testing. Principal components analysis, cluster analysis, and population partitioning, along with a Geographical Information System, were used to decipher groundwater flow patterns in Oasis Valley, Nevada. These multivariate statistical techniques were applied to the trace element chemistry of groundwater samples collected from 26 springs and wells within Oasis Valley, the NTS, and the Nellis Air Force Range. The results of all statistical analyses showed similar geographical trends in the trace element chemistry of the groundwaters included in this study. Differences are observed between the groundwaters from the NTS and those of Oasis Valley based on the concentrations of the elements Li, Ge, Mo, Rb, Ba, U, and Ru. A concentration gradient is observed from lower concentrations in the NTS to increasing concentrations toward Oasis Valley suggesting groundwater flow in an overall southwestward direction from the NTS. Also, a different trace element signature is observed for the waters collected in the northern and western region of Oasis Valley, suggesting another source of groundwater to this area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007522519268
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  • 10
    Electronic Resource
    Electronic Resource
    Preliminary assessment of a nonlinear mapping algorithm in a geological context (1973)
    Springer
    Mathematical geology 5 (1973), S. 39-57 
    Details
    ISSN: 1573-8868
    Keywords: classification ; cluster analysis ; dimensionality reduction ; mapping ; multivariate analysis ; principal-components analysis ; general geology ; geochemistry ; paleontology ; petrology ; stratigraphy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A new algorithm has been developed by J. W. Sammon for the nonlinear-point mapping of high-dimensional data in two dimensions such that the inherent structure of the data is approximately preserved. This paper describes results using several sets of geologic data including stratigraphic thickness, petrographic modal analysis, and morphological or geochemical measurements. Comparisons are made with hierarchical cluster analysis using dendrogram representation. Initial results are encouraging and suggest that the technique could have widespread geological applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02114086
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