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181.
182.
Separation of local and regional information in distorted GDS response functions by hypothetical event analysis 总被引:2,自引:0,他引:2
Electromagnetic investigations are usually intended to examine regional structures where induction takes place at a given period range. However, the regional information is often distorted by galvanic effects at local conductivity boundaries. Bahr (1985) and Groom & Bailey (1989) developed a physical distortion model for decomposing the MT impedance tensor, based upon local galvanic distortion of a regional 2-D electromagnetic field. We have extended their method to predict the magnetic variation fields created at an array of sites. The magnetic response functions at periods around 1000 s may be distorted by large-scale inhomogeneities in the upper or middle crust. In this period range, the data measured by a magnetometer array contain common information that can be extracted if the data set is treated as a unit, for example by using hypothetical event analysis. With this technique it is always possible to recover the regional strike direction from distorted data, even if a strong, spatially varying regional vertical field component is present in the data set. The determination of the regional impedance phases, on the other hand, is far more sensitive to deviations from the physical distortion model.
The approach has been used to investigate the Iapetus data set. For the array, which covers an area of 200 km × 300 km in northern England/southern Scotland, the technique revealed a common regional strike azimuth of ca . N125° E in the period range 500–2000 s. This direction differs from the strike indicated by the induction arrows, which seem influenced mainly by local current concentrations along the east–west-striking Northumberland Trough and a NE–SW-striking mid-crustal conductor. Both impedance phases are positive and differ by ca . 10°, which supports the assumptions of distortion fields in the data set and that the regional structure is 2-D. 相似文献
The approach has been used to investigate the Iapetus data set. For the array, which covers an area of 200 km × 300 km in northern England/southern Scotland, the technique revealed a common regional strike azimuth of ca . N125° E in the period range 500–2000 s. This direction differs from the strike indicated by the induction arrows, which seem influenced mainly by local current concentrations along the east–west-striking Northumberland Trough and a NE–SW-striking mid-crustal conductor. Both impedance phases are positive and differ by ca . 10°, which supports the assumptions of distortion fields in the data set and that the regional structure is 2-D. 相似文献
183.
B. John Makario Londoño A. John Jairo Sanchez E. Luis Eduardo Toro Fernando Gil Cruz Olga Patricia Bohorquez 《Bulletin of Volcanology》1998,59(8):556-561
Coda Q–1 was calculated at Nevado del Ruiz Volcano (NRV) before and after two phreatomagmatic eruptions (November 1985, September
1989) and for a period of stability (May 1987) using a functional form for coda derived from a single scattering model (Sato
1977). Substantial changes were found before and after the eruptions. The highest value of Q–1 was found during the November 1985 eruption, an intermediate value for the September 1989 eruption, and the lowest value
for May 1987. It seems that the changes in coda Q–1 at NRV have a still-unknown relationship with the volume or magnitude of the eruption. A relatively strong frequency dependence
was found for all periods. Also Q–1 clearly changed with time, suggesting that the scattering was strong for the eruption of November 1985 and decreased for
the eruption of September 1989, and that the intrinsic absorption probably increased. This suggests the possibility that crystallization
is taking place in the NRV magma. The clear change of coda Q–1 before and after the eruptions at NRV also suggests the possibility that coda Q–1 is a premonitory tool of activity at this volcano.
Received: 25 October 1996 / Accepted: 21 January 1998 相似文献
184.
Michael Feast Frederic Pont & Patricia Whitelock 《Monthly notices of the Royal Astronomical Society》1998,298(2):L43-L44
A value for the zero-point (ρ) of the Cepheid period–luminosity relation, < M V >= 2.81 log P + ρ, is deduced by comparing the value of the Oort constant, A , derived from radial velocities with that derived from Hipparcos proper motions. We find in this way that ρ =−1.47 ± 0.13, in excellent agreement with the value derived from Hipparcos trigonometrical parallaxes, ρ = −1.43 ± 0.10, by Feast &38; Catchpole in a recent paper. 相似文献
185.
Two deterministic models were combined: one for canopy leaf energy budgets and one for street canyon energy budgets. The effects of street parks and roof gardens in contrast to non-vegetated city blocks were examined by the use of four typical urban morphologies, which were exposed latitudinally to summer and winter simulations. A variety of increases and decreases in shortwave radiation, net radiation, sensible heat flux, and system reradiation resulted. These changes appear to represent the generalized limits of the possible responses to the addition of vegetation to non-vegetated city blocks. 相似文献
186.
Summary The green feldspar in alkali granite from the Avdar deposit of decoration stone (150 km W of Ulan-Bator) has been identified by means of physical and chemical methods as amazonite. Its structural state corresponds to that of microcline with a high degree of triclinicity and displaying the following anomalous dimensions of the unit cell (nm):a=0.8568,b=1.2967,c=0.7217 nm, =90.732, =115.851, =87.702°;V=0.72115 nm3.The amazonite contains in increased amount of Pb (1950 ppm) as well as of Rb (1.15 mass %). The genesis of this amazonite is associated with younger metasomatic processes in the alkali granite.
With 1 Figure 相似文献
Amazonit aus dem Alkali-Granit des Avdar-Massivs, Mongolei
Zusammenfassung Der grüne Feldspat im Alkaligranit aus der Dekorationsstein-Lagerstätte im Avdar Massiv (150 km W von Ulan-Bator) wurde auf Grund physikalischer und chemischer Methoden als Amazonit bestimmt. Sein Strukturzustand entspricht demjenigen eines Mikroklins, der eine hohe Triklinität und anomale Elementarzelle aufweist (in nm):a=0.8568,b=1.2967,c=0.7217 nm, =90.732, =115.851, =87.702°;V=0.72115 nm3.Der Amazonit hat einen erhöhten Gehalt an Pb (1950 ppm) und an Rb (1.15 Gew.-%). Die Genesis dieses Amazonits ist mit jüngeren metasomatischen Prozessen im Alkaligranit verknüpft.
With 1 Figure 相似文献
187.
Josef Bochníček Tomáš Zelinka Reviewer T. Kolbenheyer 《Studia Geophysica et Geodaetica》1981,25(4):411-412
Summary The authors prove that the solution of Laplace's equation under Neumann's boundary conditions can be transformed to an advantage into determining the field which is generated by charges, induced by the external field at surfaces of discontinuity. 相似文献
188.
Summary The changes of the anisotropy of magnetic susceptibility of igneous rocks, induced by a magnetic field, are studied. It is proved that changes in the degree of anisotropy of susceptibility and of the orientation of the susceptibility ellispoid of specimens occur due to the configuration of the domain structure under the effect of the magnetic field. The influence of this effect on the total anisotropy of rocks depends on the degree of anisotropy due to the shape factor and on the stability of the domain structure. A model concept is presented, explaining the qualitatively different pattern of the changes of the anisotropy of susceptibility under the effect of the magnetic field in various directions of the specimens. 相似文献
189.
Summary A new computer-oriented algorithm GSO is presented for solving overdetermined systems of linear observation equations according to the principle of the least-squares method. The matrix of the system of observation equations may be of deficient rank. In this case the algorithm leads to the vector of unknowns with a minimum Euclidean norm. Alternatively, it is possible to minimize the norm of a subvector formed by a selected group of unknowns. The weight coefficient matrix, corresponding to the vector (subvector) of unknows, has the least possible trace. The algorithm GSO is based on the Gram-Schmidt Orthogonalization of suitably defined augmented matrices. The establishing and solving of normal equations is not necessary. Apart from the unknowns and residuals, GSO also determines the factorized weight coefficient matrices of the adjusted values.Presented at the I.A.G. International Symposium on Optimization of Design and Computation of Control Networks, Sopron, Hungary 1977. 相似文献
190.
Summary The problem of the elastic properties of a medium composed of thin anisotropic layers is treated. The study is based on the conditions of stress and strain and on Hooke's Law under the assumption of close contact between the layers. The algorithm described is suitable for a computer.Dedicated to RNDr. Jan Pícha, CSc., on his 60th Birthday 相似文献