COHERENCE FUNCTIONS FOR MAGNETOTELLURIC ANALYSIS

Geophysics ◽  
1974 ◽  
Vol 39 (3) ◽  
pp. 312-320 ◽  
Author(s):  
I. K. Reddy ◽  
D. Rankin
Keyword(s):  
Data Analysis ◽  
Linear System ◽  
System Approach ◽  
Partial Coherence ◽  
Impedance Method ◽  
Two Dimensional ◽  
Magnetotelluric Data ◽  
The Earth ◽  
Principal Axes ◽  
Tensor Impedance

A multiinput linear system approach is used to study the magnetotelluric phenomena in the presence of lateral conductivity inhomogeneities in the earth. The three types of coherence functions (ordinary, multiple, and partial) are defined, and their use in magnetotelluric data analysis is illustrated with a field example. Partial coherence functions are used to determine the principal axes in the case of two‐dimensional type inhomogeneities, and as measures of three‐dimensionality in the case of non‐two‐dimensional type structures. The results obtained using coherence functions are compared with those obtained with the conventional tensor impedance method.

scholarly journals Model of the propagation of very low-frequency beams in the Earth–ionosphere waveguide: principles of the tensor impedance method in multi-layered gyrotropic waveguides

2020 ◽  
Vol 38 (1) ◽  
pp. 207-230
Author(s):  
Yuriy Rapoport ◽  
Vladimir Grimalsky ◽  
Viktor Fedun ◽  
Oleksiy Agapitov ◽  
John Bonnell ◽  
...  
Keyword(s):  
Optical Waveguides ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Signal Propagation ◽  
Wide Frequency Range ◽  
Impedance Method ◽  
Very Low Frequency ◽  
The Earth ◽  
Tensor Impedance ◽  
Electromagnetic Beams

Abstract. The modeling of very low-frequency (VLF) electromagnetic (EM) beam propagation in the Earth–ionosphere waveguide (WGEI) is considered. A new tensor impedance method for modeling the propagation of electromagnetic beams in a multi-layered and inhomogeneous waveguide is presented. The waveguide is assumed to possess the gyrotropy and inhomogeneity with a thick cover layer placed above the waveguide. The influence of geomagnetic field inclination and carrier beam frequency on the characteristics of the polarization transformation in the Earth–ionosphere waveguide is determined. The new method for modeling the propagation of electromagnetic beams allows us to study the (i) propagation of the very low-frequency modes in the Earth–ionosphere waveguide and, in perspective, their excitation by the typical Earth–ionosphere waveguide sources, such as radio wave transmitters and lightning discharges, and (ii) leakage of Earth–ionosphere waveguide waves into the upper ionosphere and magnetosphere. The proposed approach can be applied to the variety of problems related to the analysis of the propagation of electromagnetic waves in layered gyrotropic and anisotropic active media in a wide frequency range, e.g., from the Earth–ionosphere waveguide to the optical waveband, for artificial signal propagation such as metamaterial microwave or optical waveguides.

scholarly journals KẾT QUẢ XỬ LÝ BƯỚC ĐẦU SỐ LIỆU ĐO SÂU TỪ TELUA TUYẾN HÒA BÌNH - THÁI NGUYÊN VÀ TUYẾN THANH HÓA - HÀ TÂY

2011 ◽  
Vol 33 (1) ◽  
pp. 18-28 ◽  
Author(s):  
Lê Huy Minh ◽  
Đinh Văn Toàn ◽  
Võ Thanh Sơn ◽  
Nguyễn Chiến Thắng ◽  
Nguyễn Bá Duẩn ◽  
...  
Keyword(s):  
Cross Sections ◽  
Active Fault ◽  
Red River ◽  
Seismic Exploration ◽  
Two Dimensional ◽  
Data Recording ◽  
Magnetotelluric Data ◽  
The Earth ◽  
Deep Faults ◽  
Hoa Binh

Preliminary results of processing the sounding magnetotelluric data of Hoa Binh - Thai Nguyen and Thanh Hoa - Ha Tay profilesTwo magnetotelluric surveys from Hoa Binh (HB) to Thai Nguyen (TN) and from Thanh Hoa (TH) to Ha Tay (HT) have been carried out. The lengths of these profiles are about more than 120 km with 33 stations (HB-TN), and with 31 stations (TH-HT). The geoelectrical cross-sections along two profiles obtained by two-dimensional inversion of the magnetotelluric data, recording interval ranges from 10-3 to 103 s are presented. It is shown that the main faults such as Muong La-Bac Yen, Red River, Chay River and Lo River on the HB-TN profile; Ma River, Son La and Kim Boi on the THHT one, could be recognized by rapid resistivity changes in the crust resistivity models. They are all trans-crustal deep faults with the vertical or nearly vertical dip. Assuming the Earth crust of three layers: upper, middle and lower with the depths of about 1-4km, 14-17km and 30-37km, respectively, from the seismic exploration data, the 1D geoelectrical models are obtained by using the MT software. It is shown that the middle crust’s resistivity is significantly higher than the lower and upper one, but the each layer is not homogeneous conductively. The resistivity decreases clearly in the active fault (Red River, Chat River Lo River…) zones, which could be related to the metamorphism releasing heats andfluids or upwelling of the mantle.

Molecular Dynamics Simulations of Shock-Defect Interactions in Two-Dimensional Nonreactive Crystals

1992 ◽  
Vol 296 ◽  
Author(s):  
Robert S. Sinkovits ◽  
Lee Phillips ◽  
Elaine S. Oran ◽  
Jay P. Boris
Keyword(s):  
Molecular Dynamics ◽  
Hexagonal Lattice ◽  
Square Lattice ◽  
Two Dimensional ◽  
Connection Machine ◽  
Defect Sites ◽  
Principal Axes ◽  
Shock Motion ◽  
Defect Interactions ◽  
Dynamics Simulations

AbstractThe interactions of shocks with defects in two-dimensional square and hexagonal lattices of particles interacting through Lennard-Jones potentials are studied using molecular dynamics. In perfect lattices at zero temperature, shocks directed along one of the principal axes propagate through the crystal causing no permanent disruption. Vacancies, interstitials, and to a lesser degree, massive defects are all effective at converting directed shock motion into thermalized two-dimensional motion. Measures of lattice disruption quantitatively describe the effects of the different defects. The square lattice is unstable at nonzero temperatures, as shown by its tendency upon impact to reorganize into the lower-energy hexagonal state. This transition also occurs in the disordered region associated with the shock-defect interaction. The hexagonal lattice can be made arbitrarily stable even for shock-vacancy interactions through appropriate choice of potential parameters. In reactive crystals, these defect sites may be responsible for the onset of detonation. All calculations are performed using a program optimized for the massively parallel Connection Machine.

The habitable zone of Earth-mass planets around 47 UMa: results for land and water worlds

2003 ◽  
Vol 2 (1) ◽  
pp. 35-39 ◽  
Author(s):  
S. Franck ◽  
M. Cuntz ◽  
W. von Bloh ◽  
C. Bounama
Keyword(s):  
Surface Water ◽  
System Approach ◽  
Distinct Type ◽  
Integrated System ◽  
Habitable Zone ◽  
Stable Orbit ◽  
The Earth ◽  
Earth Like Planets ◽  
Very High

In a previous paper, we showed that Earth-type habitable planets around 47 UMa are in principle possible if a distinct set of conditions is warranted. These conditions include that the Earth-type planets have successfully formed and are orbitally stable and, in addition, that the 47 UMa star–planet system is relatively young ([lsim ]6 Gyr). We now extend this study by considering Earth-like planets with different land/ocean coverages. This study is again based on the so-called integrated system approach, which describes the photosynthetic biomass production taking into account a variety of climatological, biogeochemical and geodynamical processes. This approach implies a special characterization of the habitable zone defined for a distinct type of planet. We show that the likelihood of finding a habitable Earth-like planet on a stable orbit around 47 UMa critically depends on the percentage of the planetary land/ocean coverage. The likelihood is significantly increased for planets with a very high percentage of ocean surface (‘water worlds’).

scholarly journals The zoo of starspots

2010 ◽  
Vol 6 (S273) ◽  
pp. 174-180 ◽  
Author(s):  
Klaus G. Strassmeier
Keyword(s):  
Data Analysis ◽  
Time Scales ◽  
Light Curves ◽  
Doppler Imaging ◽  
Dependent Data ◽  
Two Dimensional ◽  
One Dimensional

AbstractStarspots are being observed with many different techniques but not always with coherent results. In particular not if model-dependent data analysis must be employed, e.g. through two-dimensional spot modelling of one-dimensional photometric light curves. I review the zoo of currently available physical spot parameters, i.e. their size, temperature and variability time scales, and also compare results from different techniques. Most of the current values come from Doppler imaging and multi-color photometry. I also list a few cases where starspot detections turned out to be very different to the solar analog.

scholarly journals A PRECONDITIONED METHOD FOR THE SOLUTION OF THE ROBBINS PROBLEM FOR THE HELMHOLTZ EQUATION

2010 ◽  
Vol 52 (1) ◽  
pp. 87-100 ◽  
Author(s):  
JIANG LE ◽  
HUANG JIN ◽  
XIAO-GUANG LV ◽  
QING-SONG CHENG
Keyword(s):  
Linear System ◽  
Helmholtz Equation ◽  
Analytical Formula ◽  
System Of Equations ◽  
Two Dimensional ◽  
Sparse System ◽  
Sine Transform ◽  
Minimum Residual ◽  
Preconditioned Matrix ◽  
Preconditioned Iterative

AbstractA preconditioned iterative method for the two-dimensional Helmholtz equation with Robbins boundary conditions is discussed. Using a finite-difference method to discretize the Helmholtz equation leads to a sparse system of equations which is too large to solve directly. The approach taken in this paper is to precondition this linear system with a sine transform based preconditioner and then solve it using the generalized minimum residual method (GMRES). An analytical formula for the eigenvalues of the preconditioned matrix is derived and it is shown that the eigenvalues are clustered around 1 except for some outliers. Numerical results are reported to demonstrate the effectiveness of the proposed method.

scholarly journals Matahari dalam Perspektif Sains dan Al-Qur'an

2019 ◽  
Vol 2 (1) ◽  
pp. 27-35
Author(s):  
Anisa Nur Afida ◽  
Yuberti Yuberti ◽  
Mukarramah Mustari
Keyword(s):  
Qualitative Research ◽  
Data Analysis ◽  
Solar System ◽  
Data Model ◽  
Research Method ◽  
The Sun ◽  
Data Display ◽  
The Earth ◽  
Library Research ◽  
Analysis Technique

Abstract: This study aims to determine the function of the sun in the perspective of science and al-Qur'an . The research method used is qualitative research methods with the type of research library (Library Research). This research applies data analysis technique of Milles and Huberman model, with steps: 1) data reduction; 2) data display; 3) verification. The result of this research is, the theories that science explain related to the function of the sun in accordance with what is also described in the Qur'an. Science explains that the sun as the greatest source of light for the earth can produce its own energy. This is explained in the Qur'an that the sun is described as siraj and dhiya' which means sunlight is sourced from itself, as the center of the solar system is not static but also moves this matter in the Qur'an explained in QS Yāsin verse 38, besides science and the Qur'an also equally explain that the sun can be made as a calculation of time.Abstrak: Penelitian ini bertujuan untuk mengetahui fungsi matahari dalam perspektif sains dan al-Qur’an..Metode penelitian yang digunakan yaitu metode penelitian kualitatif dengan jenis penelitian pustaka (Library Research). Penelitian ini menggunakan teknik analisis data model Milles dan Huberman, dengan langkah-langkah: 1) reduksi data; 2) display data; 3) verifikasi. Hasil dari penelitian ini yaitu, teori-teori yang sains jelaskan berkaitan dengan fungsi matahari sesuai dengan apa yang juga di jelaskan dalam al-Qur’an. Sains menjelaskan bahwa matahari sebagai sumber energi cahaya terbesar bagi bumi dapat menghasilkan energinya sendiri hal ini dijelaskan dalam al-Qur’an bahwa matahari dideskripsikan sebagai siraj dan dhiya’yang berarti sinar matahari bersumber dari dirinya sendiri, sebagai pusat tata surya matahari tidaklah statis melainkan juga bergerak hal ini dalam al-Qur’an di jelaskan dalam QS Yāsin ayat 38, selain itu sains dan al-Qur’an juga sama-sama menjelaskan bahwa matahari  dapat di jadikan sebagai perhitungan waktu serta petunjuk dari bayang-bayang.

JOINT 3D TRAVELTIME INVERSION OF P, S AND CONVERTED WAVES

2001 ◽  
Vol 09 (04) ◽  
pp. 1407-1416 ◽  
Author(s):  
GIULIANA ROSSI ◽  
ALDO VESNAVER
Keyword(s):  
Linear System ◽  
Seismic Waves ◽  
Velocity Fields ◽  
Traveltime Inversion ◽  
S Waves ◽  
The Earth ◽  
Converted Waves

Converted waves can play a basic role in the traveltime inversion of seismic waves. The sought velocity fields of P and S waves are almost decoupled, when considering pure P and S arrivals: their only connection are the possible common reflecting interfaces in the Earth. Converted waves provide new equations in the linear system to be inverted, which directly relates the two velocity fields. Since the new equations do not introduce additional unknowns, they increase the system rank or its redundancy, so making its solutions better constrained and robust.

Sign in / Sign up

Export Citation Format

Share Document