The Earth’s Free Spherical Oscillations of the Great Japan Earthquake

An M9.0 earthquake struck Japan on March 11, 2011 and the strong earthquake made continuous oscillation of the Earth. We first studied the Earth’s free oscillations using observations of VHZ channel of China Digital Seismic Network (CDSN). Since the frequency response of seismograph in CDSN suppresses the information of low frequency signal, we do not need to remove the solid tide in our data processing. We extracted 72 clear spherical modes of (0S0,0S2to0S72) of the Earth’s free oscillation and 21 harmonic modes and they are consistent and nearly same with the frequencies of the modes of Preliminary Reference Earth Model (PREM). Spectral splitting phenomenon is observed obviously in0S2,0S3,0S4and1S2free oscillation modes.

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The Earth’s Free Spherical Oscillations of the Chile Earthquake

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.622-623.1674 ◽

2012 ◽

Vol 622-623 ◽

pp. 1674-1681

Author(s):

Ye Wu ◽

Shu Yang ◽

Liang Ding

Keyword(s):

Free Oscillation ◽

Low Frequency ◽

Earth Model ◽

The Earth ◽

Oscillation Modes ◽

Chile Earthquake ◽

Spectral Splitting ◽

Earth’S Free Oscillations ◽

Earth’S Free Oscillation ◽

Digital Seismic Network

An M8.8 earthquake struck Chile on February 27, 2010 and the strong earthquake made continuous oscillation of the Earth. We studied the Earth’s free oscillations using observations of VHZ channel of China Digital Seismic Network (CDSN). Since the frequency response of seismograph in CDSN suppresses the information of low frequency signal, we do not need to remove the solid tide in our data processing. We extracted 76 clear spherical modes of (0S0, 0S2 to 0S76) of the Earth’s free oscillation and 78 harmonic modes and they are consistent and nearly same with the frequencies of the modes of Preliminary Reference Earth Model (PREM). Spectral splitting phenomenon is observed obviously in 0S2, 0S3, 0S4 and 1S2 free oscillation modes.

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A LOW FREQUENCY ELECTRICAL EARTH MODEL

Geophysics ◽

10.1190/1.1438195 ◽

1955 ◽

Vol 20 (4) ◽

pp. 860-870 ◽

Cited By ~ 2

Author(s):

William C. Pritchett

Keyword(s):

Low Frequency ◽

Salt Dome ◽

Earth Model ◽

Model Surface ◽

Inductively Coupled ◽

The Earth ◽

Surface Measurements ◽

Minor Anomalies ◽

Model Equations

A general earth model is described which simulates the earth when excited by currents either conductively coupled to the earth by electrodes or inductively coupled to the earth by loops. Consideration of model equations showed that a material with a resistivity of approximately [Formula: see text] ohm‐meters was desired for use in the model. Although suitable materials with this resistivity were not known, it was found that fine bronze wheel grindings held together by wax did have the required macroscopic resistivity. Using this model, surface measurements were made employing a modified Wenner spread “one mile” in length. Only minor anomalies resulted from a simulated salt dome “three‐quarters of a mile” in diameter and “one‐half mile” below the surface.

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Two difference schemes for the numerical solution of Maxwell’s equations as applied to extremely and super low frequency signal propagation in the Earth-ionosphere waveguide

Computational Mathematics and Mathematical Physics ◽

10.1134/s0965542514100030 ◽

2014 ◽

Vol 54 (10) ◽

pp. 1597-1617

Author(s):

O. I. Akhmetov ◽

V. S. Mingalev ◽

I. V. Mingalev ◽

O. V. Mingalev ◽

Yu. V. Fedorenko

Keyword(s):

Numerical Solution ◽

Maxwell’S Equations ◽

Maxwell's Equations ◽

Low Frequency ◽

Signal Propagation ◽

Difference Schemes ◽

Frequency Signal ◽

The Earth

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FrosPy: A Modular Python Toolbox for Normal Mode Seismology

Seismological Research Letters ◽

10.1785/0220210208 ◽

2022 ◽

Author(s):

Simon Schneider ◽

Sujania Talavera-Soza ◽

Lisanne Jagt ◽

Arwen Deuss

Keyword(s):

Normal Mode ◽

Free Oscillation ◽

Large Time ◽

Reference Model ◽

Normal Modes ◽

Earth Model ◽

Splitting Function ◽

Quality Factor Q ◽

Earth’S Free Oscillation ◽

Q Values

Abstract We present free oscillations Python (FrosPy), a modular Python toolbox for normal mode seismology, incorporating several Python core classes that can easily be used and be included in larger Python programs. FrosPy is freely available and open source online. It provides tools to facilitate pre- and postprocessing of seismic normal mode spectra, including editing large time series and plotting spectra in the frequency domain. It also contains a comprehensive database of center frequencies and quality factor (Q) values based on 1D reference model preliminary reference Earth model for all normal modes up to 10 mHz and a collection of published measurements of center frequencies, Q values, and splitting function (or structure) coefficients. FrosPy provides the tools to visualize and convert different formats of splitting function coefficients and plot these as maps. By giving the means of using and comparing normal mode spectra and splitting function measurements, FrosPy also aims to encourage seismologists and geophysicists to learn about normal mode seismology and the study of the Earth’s free oscillation spectra and to incorporate them into their own research or use them for educational purposes.

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Universal dispersion tables

Bulletin of the Seismological Society of America ◽

10.1785/bssa0590041667 ◽

1969 ◽

Vol 59 (4) ◽

pp. 1667-1693

Author(s):

Don L. Anderson ◽

Robert L. Kovach

Keyword(s):

Upper Mantle ◽

Free Oscillation ◽

Velocity Structure ◽

Shear Velocity ◽

Average Density ◽

Earth Model ◽

The Core ◽

The Earth ◽

Small Change ◽

Dominant Parameter

Abstract The effect of a small change in any parameter of a realistic Earth model on the periods of free oscillation is computed for both spheroidal and torsional modes. The normalized partial derivatives, or variational parameters, are given as a function of order number and depth in the Earth. For a given mode it can immediately be seen which parameters and which regions of the Earth are controlling the period of free oscillation. Except for oSo and its overtones the low-order free oscillations are relatively insensitive to properties of the core. The shear velocity of the mantle is the dominant parameter controlling the periods of free oscillation and density can be determined from free oscillation data only if the shear velocity is known very accurately. Once the velocity structure is well known free oscillation data can be used to modify the average density of the upper mantle. The mass and moment of inertia are then the main constraints on how the mass must be redistributed in the lower mantle and core.

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