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1.
An example of magnetotelluric data is discussed which has distinctive phase values out of quadrant, and for which the Zxx element of the measured tensor is greater than the Zxy element in both real and quadrature parts. Mohr circle plots and principal value decompositions of the real and quadrature parts of the tensor clarify its understanding. An analysis of rotational invariants of the data suggests a case of galvanic distortion of a 2D structure. Results from phase tensor analysis are included, and the example is seen to be a dramatic instance of phase tensor analysis reducing an apparently 3D example to 2D characteristics.The Mohr circles of this example do not capture the axes origin, although there are phases out of quadrant. Extra intrigue is thus added to the question, noted in Lilley, F.E.M., 1998. Magnetotelluric tensor decomposition: part I, theory for a basic procedure. Geophysics 63, 1885–1897 and arising independently in Caldwell, T.G., Bibby, H. M., Brown, C., 2004. The magnetotelluric phase tensor. Geophys. J. Int. 158, 457–469 and Bibby, H.M., Caldwell, T.G., Brown, C., 2005. Determinable and non-determinable parameters of galvanic distortion in magnetotellurics. Geophys. J. Int. 163, 915–930, whether the determinant values taken separately of the real and quadrature parts of a magnetotelluric tensor should both never be negative.For data whose Mohr circles do not capture the axes origin, simple conditions are derived regarding phase. These conditions govern whether or not it is formally possible for observed phases of Zxy to exceed 90°, for any rotation of the observing axes. 相似文献
2.
F.H. Chamalaun S.N. Prasad F.E.M. Lilley B.J. Srivastava B.P. Singh B.R. Arora 《Tectonophysics》1987,140(2-4):247-255
The geomagnetic variation data from the 1979 Indian array experiment have been reanalyzed and reexamined using the hypothetical event analysis technique. The contour map of the |Z/H ratio replicates distinctive anomaly in northwest India previously delineated in maps of the Fourier coefficients. The anomaly reveals the presence of a significant conductor under the Ganga basin. The contour map has been used to derive a response profile perpendicular to the strike of the anomaly, for comparison with 2-D numerical models. An excellent fit was found for a conductor at a depth of 32 km, with a width of 110 km and a conductivity contrast of 1000. This result places the conductor deep within the lithosphere. In the absence of supporting data the origin of the conductor is difficult to resolve. However, it is thought to be related to pressure-released partial melting, caused by fracturing of the Indian crust during the collision of India with Asia. 相似文献
3.
R Shirani Faradonbeh D Jahed Armaghani M. Z. Abd Majid M. MD Tahir B. Ramesh Murlidhar M. Monjezi H. M. Wong 《International Journal of Environmental Science and Technology》2016,13(6):1453-1464
Blasting is a widely used technique for rock fragmentation in opencast mines and tunneling projects. Ground vibration is one of the most environmental effects produced by blasting operation. Therefore, the proper prediction of blast-induced ground vibrations is essential to identify safety area of blasting. This paper presents a predictive model based on gene expression programming (GEP) for estimating ground vibration produced by blasting operations conducted in a granite quarry, Malaysia. To achieve this aim, a total number of 102 blasting operations were investigated and relevant blasting parameters were measured. Furthermore, the most influential parameters on ground vibration, i.e., burden-to-spacing ratio, hole depth, stemming, powder factor, maximum charge per delay, and the distance from the blast face were considered and utilized to construct the GEP model. In order to show the capability of GEP model in estimating ground vibration, nonlinear multiple regression (NLMR) technique was also performed using the same datasets. The results demonstrated that the proposed model is able to predict blast-induced ground vibration more accurately than other developed technique. Coefficient of determination values of 0.914 and 0.874 for training and testing datasets of GEP model, respectively show superiority of this model in predicting ground vibration, while these values were obtained as 0.829 and 0.790 for NLMR model. 相似文献
4.
5.
F.E.M. Lilley 《Physics of the Earth and Planetary Interiors》1974,8(4):301-316
The geomagnetic induction tensor is a means of summarizing the response of the earth at a given observing site to a geomagnetic variation source field. In this paper the characteristics of the tensor elements are examined, both generally and for the special cases of one-dimensional and two-dimensional geologic structure. The first-order model is taken of uniform source fields originating external to a semi-infinite half-space. Graphical ways of presenting the information contained in an induction tensor are explored, including ellipses of rotation, polar diagrams, and diagrams analogous to the Mohr circles of elasticity theory. Criteria to distinguish “two-dimensional” data from “three-dimensional” data are established. The advantages of simultaneously recording “normal” and “anomalous” variations are demonstrated in terms of the extra tensor elements which may then be estimated. The most practical way of presenting information from many stations on a map may be by drawing, for each site, arrows which summarize the response in the vertical field and quadrics which summarize the response in the horizontal field. 相似文献
6.
7.
8.
C K CHANG H MD AZAMATHULLA N A ZAKARIA A AB GHANI 《Journal of Earth System Science》2012,121(1):125-133
This paper evaluates the performance of three soft computing techniques, namely Gene-Expression Programming (GEP) (Zakaria
et al 2010), Feed Forward Neural Networks (FFNN) (Ab Ghani et al 2011), and Adaptive Neuro-Fuzzy Inference System (ANFIS) in the prediction of total bed material load for three Malaysian
rivers namely Kurau, Langat and Muda. The results of present study are very promising: FFNN (R
2 = 0.958, RMSE = 0.0698), ANFIS (R
2 = 0.648, RMSE = 6.654), and GEP (R
2 = 0.97, RMSE = 0.057), which support the use of these intelligent techniques in the prediction of sediment loads in tropical
rivers. 相似文献
9.
10.
Low temperature volatile production at the Lost City Hydrothermal Field, evidence from a hydrogen stable isotope geothermometer 总被引:1,自引:0,他引:1
Giora Proskurowski Marvin D. Lilley Deborah S. Kelley Eric J. Olson 《Chemical Geology》2006,229(4):331-343
Although commonly utilized in continental geothermal work, the water-hydrogen and methane-hydrogen isotope geothermometers have been neglected in hydrothermal studies. Here we report δD-CH4 and δD-H2 values from high-temperature, black smoker-type hydrothermal vents and low-temperature carbonate-hosted samples from the recently discovered Lost City Hydrothermal Field. Methane deuterium content is uniform across the dataset at − 120 ± 12‰. Hydrogen δD values vary from − 420‰ to − 330‰ at high-temperature vents to − 700‰ to − 600‰ at Lost City. The application of several geothermometer equations to a suite of hydrothermal vent volatile samples reveals that predicted temperatures are similar to measured vent temperatures at high-temperature vents, and 20-60 °C higher than those measured at the Lost City vents. We conclude that the overestimation of temperature at Lost City reflects 1) that methane and hydrogen are produced by serpentinization at > 110 °C, and 2) that isotopic equilibrium at temperatures < 70 °C is mediated by microbial sulfate reduction. The successful application of hydrogen isotope geothermometers to low-temperature Lost City hydrothermal samples encourages its employment with low-temperature diffuse hydrothermal fluids. 相似文献