On the vertical component of the Earth-current in mountainous regions

1932 ◽  
Vol 37 (3) ◽  
pp. 406
Author(s):  
J. G. Koenigsberger
Keyword(s):  
Vertical Component ◽  
Mountainous Regions ◽  
The Earth

Subsidence in the European Area

1934 ◽  
Vol 71 (2) ◽  
pp. 76-85
Author(s):  
R. G. Lewis
Keyword(s):  
Central Europe ◽  
Outer Layer ◽  
The Other ◽  
Dense Layer ◽  
Total Thickness ◽  
Mountainous Regions ◽  
European Area ◽  
The Earth ◽  
Granitic Layer ◽  
Sedimentary Layer

The structure of the earth was supposed by Suess to be tripartite, there was an outer layer of rocks mainly granitic, the sal, or sial as it is usually now called. This rested, or “floated”, on a dense layer called the sima, of basaltic character, within which was the earth’s core, or nife, metallic in nature. Such a simple conception has been modified in the light of later knowledge: geologically there is much evidence pointing to the existence of several shells of increasing density within the crust. This is to some extent supported by the evidence of seismology, the layers below the upper sedimentary layer being the Granitic, the Intermediate (of tachylyte or diorite) and Lower Layers (dunite, peridotite, or eclogite) (1). According to the latest information there are four layers intermediate between the granitic and lower layers: the thickness of the sedimentary layer varies from about 2 to 6 kilometres in mountainous regions: the thickness of the granitic layer varies, being about 10 to 12 kilometres in Central Europe. In low-lying regions the total thickness of these two layers is probably about 6 kilometres less than in mountainous regions: “the thicknesses of the other layers are very difficult to determine; the upper two probably have together a thickness of about 15 kilometres, but the others can hardly be determined from the observations” (2).

scholarly journals FORWARD MODELLING METODE GAYABERAT DENGAN MODEL INTRUSI DAN PATAHAN MENGGUNAKAN OCTAVE

2020 ◽  
Vol 4 (2) ◽  
pp. 111-117
Author(s):  
Muhammad Nurul ◽  
Syamsurijal Rasimeng ◽  
Ida Bagus Suananda Yogi ◽  
Aprillia Yulianata ◽  
Aisah Yuliantina
Keyword(s):  
Synthetic Data ◽  
Vertical Component ◽  
Model Parameters ◽  
Attraction Force ◽  
Distance Curve ◽  
Rock Density ◽  
The Earth ◽  
Fracture Modeling ◽  
Fracture Models ◽  
Acceleration Of Gravity

The gravity method is a geophysical exploration method to measure variations in the acceleration of gravity on the surface of the earth in response to variations in rocks that exist beneath the surface. In gravity exploration requires a preliminary picture as a reference for measurement. This study aims to make forward modeling synthetic OCTAVE based using synthetic data on subsurface rock structures, so as to produce intrusion and fracture models based on differences in the value of the acceleration of gravity from one point to another on the surface of the earth. Synthetic modeling with the geological parameter approach of the study area is based on variations in the price of rock density. The model parameters used in intrusion modeling are the density value of 2.7 g/cm3 and the depth of 850 meters while the fracture modeling uses a density value of 2.7 g/cm3 with a depth of 350 meters and 360 meters and a thickness of 500 meters. From intrusion modeling, the gravity vertical component of attraction force is 0.03 mGal and in the fracture modeling the gravity vertical component of attraction force is 0.0565 mGal. Based on the results of this modeling, distance curve vs. gravity anomaly response is obtained for both cases. In the intrusion rock model obtained by the profile model with an open type down. While the fracture modeling is obtained anomalous profile curve variation which states that in the fracture area with a significant change in the direction of the curve.

Terrestrial spectroscopy following the Rat Island earthquake

1966 ◽  
Vol 56 (6) ◽  
pp. 1269-1288
Author(s):  
Ali A. Nowroozi
Keyword(s):  
Cross Correlation ◽  
Vertical Component ◽  
Order Number ◽  
The Earth ◽  
Spectral Peaks ◽  
Component Strain ◽  
Strain Components ◽  
Components Analysis ◽  
Shearing Strain ◽  
Spheroidal Oscillations

Abstract Fourier analysis of the four-component strain recordings at Ogdensburg, New Jersey, after the Rat Island earthquake of February 4, 1965, has yielded spectra of the earth oscillations. Three horizontal components were used to calculate synthetic longitudinal, transverse, and shearing strain components. Analysis of the different components or their combinations yielded spectra of the torsional and spheroidal oscillations. The spectral peaks corresponding to l = 3 through l = 24 were resolved and were significantly above the 95 per cent confidence level. The novelty of this analysis is the appearance of 9 first overtones and 8 second overtones of the spheroidal oscillations from cross-correlation of two sections of the vertical component of the strain recording. The observed periods are compared to theoretical periods of four earth models: M1 of Landisman; R1 of Dorman; Jeffreys-Bullen B; and Gutenberg-Bullen A. The M1 and R1 models gave the most satisfactory agreement with the observations of the fundamental modes, whereas the Jeffreys-Bullen B model had a better agreement with the observations of the overtones than other models considered. Assuming the azimuthal order number, m, of the source as a combination of m = 0, m = 1, and m = 2, the variations of the spectral amplitudes at Ogdensburg indicated that the main contributing component of the azimuthal order number of the source was not only zero, but it was 1 for the modes corresponding to l = 2,4,7,9,12, and 2 for the modes corresponding to l = 3, 5,6,8,10, and 13.

Microseisms in the 11- to 18-second period range

1957 ◽  
Vol 47 (2) ◽  
pp. 111-127
Author(s):  
Jack Oliver ◽  
Maurice Ewing
Keyword(s):  
Deep Water ◽  
Littoral Zone ◽  
Vertical Component ◽  
Time Correlation ◽  
Period Range ◽  
The Earth ◽  
Seismograph Station ◽  
The Waves ◽  
Second Period ◽  
Wave Recorder

Abstract Storm microseisms in the 11- to 18-second period range recorded at Palisades and Bermuda are attributed to ocean swell of identical periods in the vicinity of the seacoast near the seismograph station. Evidence is based on travel time, correlation with wave-recorder data, and dispersion of the waves from hurricane Dolly, which remained in deep water when near the Palisades station and passed at a speed greater than the group velocity of ocean swell. Ground-particle motion is longitudinal, with little or no vertical component. With some qualifications, the results agree with the classical surf theory of microseism generation. Certainly, the energy is transferred to the earth within the littoral zone.

Correlation function of teleseismic noise

1968 ◽  
Vol 58 (2) ◽  
pp. 521-538
Author(s):  
K. R. Johnson
Keyword(s):  
Correlation Function ◽  
Seismic Waves ◽  
Vertical Component ◽  
Noise Spectrum ◽  
Spherically Symmetric ◽  
Seismic Arrays ◽  
The Earth ◽  
Diffraction Effects ◽  
Surface Diffraction ◽  
Surface Noise

Abstract A theoretical calculation is made of the correlation function for the vertical component of Earth motion caused by teleseismic microseismic noise. The calculation pertains to an idealized case in which the Earth is assumed to be spherically symmetric and to transmit seismic waves as a non-dispersive linear system, and in which all noise is assumed to originate at the Earth's surface. Diffraction effects are neglected. Only phases that originate and terminate as longitudinal waves are considered, although the method of analysis is readily applicable to other phases. The correlation function for teleseismic noise is calculated and plotted for the case of isotropic noise having a specific noise spectrum. The theoretical noise reduction is calculated and plotted versus average seismometer spacing for a set of seven-seismometer seismic arrays for the cases of teleseismic noise alone, surface noise alone, and a combination of teleseismic and surface noise.

THE GRAVIMETRIC DENSITY FORMULA FOR A SPHERICAL SHELL

Geophysics ◽  
1977 ◽  
Vol 42 (7) ◽  
pp. 1469-1469 ◽  
Author(s):  
J. R. Hearst ◽  
R. C. Carlson
Keyword(s):  
Spherical Shell ◽  
Gravitational Constant ◽  
Vertical Component ◽  
Horizontal Plate ◽  
Spherical Shells ◽  
Measuring Point ◽  
The Earth ◽  
Vertical Distance ◽  
Free Air ◽  
Vening Meinesz

The formula for the gravimetric density (ρ) of material, between two stations a vertical distance ΔZ apart in a borehole, is (Hammer, 1950): [Formula: see text]where k is the gravitational constant, F the free air gradient (the derivative of gravity with respect to depth in the absence of matter), and Δg the change in gravity. This formula is generally derived by integrating the vertical component of gravity caused, at a measuring point, by an infinite horizontal plate of thickness t, and then doubling it to account for one measuring point above and below the plate. This results in (Heiskanen and Vening‐Meinesz, 1958), [Formula: see text]In fact, however, the earth is not made up of infinite horizontal plates; it can perhaps more reasonably be regarded as a series of spherical shells. It is therefore instructive to derive the expression for the change in gravity associated with passing through one of these spherical shells.

scholarly journals Assessing the accuracy of SRTM altitude data for the hilly area in northeastern Romania

2018 ◽  
Author(s):  
Mihai Niculita
Keyword(s):  
High Resolution ◽  
Vertical Component ◽  
Hilly Area ◽  
The Earth ◽  
Vertical Datum ◽  
North Eastern ◽  
Elevation Data ◽  
Horizontal Wavelength ◽  
Acquisition Method ◽  
Srtm Data

SRTM data is still one of the most used data in geosciences for various purposes: geomorphometric analysis, environmental covariate modelling or geomorphic change detection. Although high resolution national/regional DEMs exist, very often accessing them is expensive, or their coverage is not complete over specific areas (only floodplains or cities are covered). Because of this SRTM still remains the best choice when elevation data is needed for regional/national or global areas. In order to assess the correctness of SRTM data to depict the real shape of Earth surface we used a regional high resolution DEM which cover a part of the hilly area of north-eastern Romanian. Both DEMs were converted to the same horizontal and vertical datum (Stereo 70 Romanian projection and the EGG97 geoid), interpolated to the same grid size and position and compared using raster algebra. The horizontal x and y components and the vertical component errors were assessed. The results show that the errors of the SRTM model are well consistent with its acquisition method (the presence of the trees and the topographic shadow) and does represent reasonably well the Earth’s surface in the study area. Anyhow, the resolution of the Earth features depicted on the SRTM model is limited by the acquisition method and does not incorporate landforms which have a vertical and horizontal wavelength under 100 m.

A Numerical computation of airflow over Iraq

2020 ◽  
Author(s):  
Firas Sabeeh Basheer1 ◽  
Wedyan Ghalib Nassif ◽  
Hazim H.Hussain Al-Saleem
Keyword(s):  
Surface Roughness ◽  
Wind Speed ◽  
Weather Forecast ◽  
Natural Properties ◽  
Mountainous Regions ◽  
The Earth ◽  
Trend Data ◽  
Bodies Of Water ◽  
The Impact ◽  
Analyze Data

Abstract The best way to understand the general atmosphere system is to collect and analyze data, identify the variables that occur in the upper and lower classes, and compare them with other values in favor of comparing them to other studies and research. Studies have been conducted in this research by analyzing the wind speed and direction and comparing it with the surface roughness to reach a concept by dividing the regions of Iraq on the basis of the surface roughness that affects the wind speed near the surface. The research aims to know the effect of air flow on the nature of the earth's surface and its effect on the different regions in Iraq. The methods used in the study depend on the hourly rates of surface roughness, wind speed and direction taken from the European-Mediterranean Weather Forecast (ECMWF) for a full year 2016 from 34 stations over Iraq. Results obtained from wind speed analysis and trend data. The highest value of wind speed (6.5 m / s) in the less rough areas (0-50 m) is concentrated in the semi-desert in the southern and western regions of the country (Anbar, Najaf and Smawa) and the lowest wind speed (1.8 m / s) for the rough areas (11- 72 m) in the mountainous regions in the northern part of the state. The importance of the results enables us to know the movement of air in this layer in terms of its weakness or strength according to the nature of the surface of the earth, as it has formed (barren lands, bodies of water, mountainous areas), which can be used in future studies to monitor the movement and speed of winds and to determine the natural properties of the air layer in contact with the surface of the earth. This requires knowledge of the impact of temperature, wind speed and direction in dividing the layers of Iraq on the basis of surface roughness.

ON THE FIELD DUE TO A VERTICAL LINE SOURCE OF CURRENT GROUNDED TO EARTH

Geophysics ◽  
1938 ◽  
Vol 3 (1) ◽  
pp. 58-62 ◽  
Author(s):  
Solomon Bilinsky
Keyword(s):  
Current Density ◽  
Line Source ◽  
Vertical Component ◽  
Radial Component ◽  
Vertical Line ◽  
Displacement Current ◽  
The Earth ◽  
Density Vector ◽  
Vertical Wire ◽  
A Current

An expression for the current density at any point in the earth due to a current in an infinitely long vertical wire is found for two types of current: (1) Simply periodic, (2) Rectangular impulse. These are given respectively by equations (11) and (13) below, where [Formula: see text] is the horizontal radial component and [Formula: see text] the vertical component of the current density vector at the point (r, z), which is at a distance R from the grounding point. These formulas hold for frequencies not too high or times not too small to allow neglect of the displacement current.

Megasource time‐domain electromagnetic sounding methods

Geophysics ◽  
1984 ◽  
Vol 49 (7) ◽  
pp. 993-1009 ◽  
Author(s):  
George V. Keller ◽  
James I. Pritchard ◽  
Jimmy Joe Jacobson ◽  
Norman Harthill
Keyword(s):  
Time Domain ◽  
Vertical Component ◽  
High Amplitude ◽  
Colorado School ◽  
Electromagnetic Sounding ◽  
The Earth ◽  
Field Versus ◽  
Time Domain Electromagnetic ◽  
Em Field ◽  
Depth Of Investigation

The Colorado School of Mines time‐domain electromagnetic (EM) sounding system makes use of a grounded length of cable powered with high‐amplitude current square waves to generate an EM field for probing the earth. The vertical component of magnetic induction is detected at a sounding site located at a relatively large distance compared to the desired depth of investigation. With a source moment of a million ampere meters or greater, offset distances of several tens of kilometers can be achieved easily, providing depths of investigation of up to 10 km. The recorded induction field versus time curves are routinely interpreted by comparison with computer‐generated theoretical curves for a layered earth. Megasource EM surveys have been carried out at The Geysers in northern California and near Yakima in central Washington, providing apparently meaningful information on the electrical structure in these areas at depths as great as 10 km.

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