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.

Characteristic periods of fundamental and overtone oscillations of the earth following a deep-focus earthquake

1972 ◽  
Vol 62 (1) ◽  
pp. 247-274 ◽  
Author(s):  
A. A. Nowroozi
Keyword(s):  
Phase Velocity ◽  
Upper Mantle ◽  
Ocean Bottom ◽  
The Earth ◽  
The Pacific ◽  
Spectral Peaks ◽  
Deep Focus ◽  
Ray Parameter ◽  
The Relationship ◽  
Spheroidal Oscillations

Abstract The deep-focus earthquake of July 31, 1970, (1.5°S, 72.6°W, h = 651 km, Mb = 7.1) excited a set of fundamental and overtone free oscillations. From analysis of seismograms recorded at Berkeley, California, at an ocean-bottom station in the Pacific, and at Ogdensburg, New Jersey, the fundamental spheroidal oscillations, l = 10-98, and a number of overtones with n = 1, 2, and 3, fundamental torsional oscillations, l = 3-70, and overtones with n = 1, 2, 3, and 4, are identified. The majority of resolved spectral peaks are above the 95 per cent confidence level. For some modes with periods less than 300 sec, the observed period at each station differs by up to 2 sec. This path-dependency of the period may thus suggest the existence of lateral heterogeneity in the upper mantle. The observed periods are compared to calculated periods for Haddon-Bullen's model HB1 and Derr's model DI-11; for fundamental modes the agreements are good, while differences up to 2 sec exist for some overtone modes. A relationship between order of oscillations, l, the frequency, nωl, and the ray parameter dt/dθ is derived, which is equivalent to the Jean's equation for phase velocity. The relationship implies that each mode with period nTl will travel with phase velocity dΔ/dt along its own ray with parameter dt/dθ. Other models will travel along the same ray if they have the same ray parameter.

scholarly journals A Sequential Autoencoder for Teleconnection Analysis

2020 ◽  
Vol 12 (5) ◽  
pp. 851 ◽  
Author(s):  
Jiena He ◽  
J. Ronald Eastman
Keyword(s):  
Time Series ◽  
Neural Representation ◽  
Strongly Correlated ◽  
Atmospheric Sciences ◽  
Teleconnection Patterns ◽  
The Earth ◽  
Unsupervised Neural Network ◽  
Residual Series ◽  
Components Analysis ◽  
Computationally Intensive

Many aspects of the earth system are known to have preferred patterns of variability, variously known in the atmospheric sciences as modes or teleconnections. Approaches to discovering these patterns have included principal components analysis and empirical orthogonal teleconnection (EOT) analysis. The latter is very effective but is computationally intensive. Here, we present a sequential autoencoder for teleconnection analysis (SATA). Like EOT, it discovers teleconnections sequentially, with subsequent analyses being based on residual series. However, unlike EOT, SATA uses a basic linear autoencoder as the primary tool for analysis. An autoencoder is an unsupervised neural network that learns an efficient neural representation of input data. With SATA, the input is an image time series and the neural representation is a unidimensional time series. SATA then locates the 0.5% of locations with the strongest correlation with the neural representation and averages their temporal vectors to characterize the teleconnection. Evaluation of the procedure showed that it is several orders of magnitude faster than other approaches to EOT, produces teleconnection patterns that are more strongly correlated to well-known teleconnections, and is particularly effective in finding teleconnections with multiple centers of action (such as dipoles).

Torsional oscillation of a homogeneous elastic spheroid

1962 ◽  
Vol 52 (3) ◽  
pp. 469-484 ◽  
Author(s):  
Tatsuo Usami ◽  
Yasuo Satô
Keyword(s):  
Fundamental Mode ◽  
Free Oscillation ◽  
Torsional Oscillation ◽  
Numerical Calculations ◽  
Higher Harmonics ◽  
Oblate Spheroidal ◽  
The Earth ◽  
Spectral Peaks ◽  
The Difference ◽  
Spheroidal Coordinates

abstract There are several causes for the observations of splitting of the spectral peaks determined from the free oscillation of the earth. In this paper, the splitting due to the ellipticity is studied assuming a homogeneous earth described by oblate spheroidal coordinates. Ellipticity causes the iTn mode to split into (n + 1) modes, while the earth's rotation causes it to split into (2n + 1) modes. 1/297.0 is adopted as the ellipticity of the earth. Numerical calculations are carried out for the fundamental mode (n = 2, 3, 4) and for the first higher harmonics (n = 1). The difference between the extreme frequencies for each value of n is 0.7% (n = 2), 0.5% (n = 3), and 0.4% (n = 4).

scholarly journals Multiscale Analysis of DInSAR Measurements for Multi-Source Investigation at Uturuncu Volcano (Bolivia)

2019 ◽  
Vol 11 (6) ◽  
pp. 703 ◽  
Author(s):  
Andrea Barone ◽  
Maurizio Fedi ◽  
Pietro Tizzani ◽  
Raffaele Castaldo
Keyword(s):  
Multiscale Analysis ◽  
Cross Correlation ◽  
Ground Deformation ◽  
Vertical Component ◽  
Central Zone ◽  
Time Interval ◽  
Volcanic Complex ◽  
Magma Body ◽  
Deep Source ◽  
Good Agreement

Uturuncu volcano (southwestern Bolivia) is localized within one of the largest updoming volcanic zones, the Altiplano Puna Volcanic Complex (APVC). In several geodetic studies the observed uplift phenomenon is analyzed and modeled by considering a deep source, related to the Altiplano Puna Magma Body (APMB). In this framework, we perform a multiscale analysis on the 2003–2010 ENVISAT satellite data to investigate the existence of a multi-source scenario for this region. The proposed analysis is based on Cross-correlation and Multiridge method, pointing out the spatial and temporal multiscale properties of the deformation field. In particular, we analyze the vertical component of ground deformation during two time interval: within the 2005–2008 time interval an inflating source at 18.7 km depth beneath the central zone of the APVC is retrieved; this result is in good agreement with those proposed by several authors for the APMB. Between August 2006 and February 2007, we identify a further inflating source at 4.5 km depth, beneath Uturuncu volcano; the existence of this latter, located just below the 2009–2010 seismic swarm, is supported by petrological, geochemical, and geophysical evidence, indicating as a possible interpretative scenario the action of shallow, temporarily trapped fluids.

IMAGE ANALYSIS BASED FINITE STRAIN MEASUREMENT OF LOCAL DEFORMATION UNDER UNIAXIAL LOAD USING NATURAL STRAIN

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Yasuyuki Kato
Keyword(s):  
Image Analysis ◽  
Strain Measurement ◽  
Finite Strain ◽  
Local Deformation ◽  
Strain Theory ◽  
Strain Behavior ◽  
Natural Strain ◽  
Strain Components ◽  
Shearing Strain ◽  
Local Deformations

This paper describes the effectiveness of image analysis based on the Natural Strain theory for measuring the finite strain. Since the additive law of strain on an identical line element can be satisfied and the rigid body rotation can clearly be removed from the shearing strain components, the Natural Strain theory is significantly effective for representing the stress-strain behavior under large elasto-plastic deformation. In this study, the strain measurements under large deformation are conducted by making use of such merits into the image analysis. In our previous studies, in order to verify the effectiveness of this method, the results of strain measurement by image analysis have been compared with the results of conventional strain measurement based on the displacement meter. Consequently, since the results of both measurements almost coincide, the validity of this image analysis has been confirmed. However, these experiments were limited to uniform deformation fields, although in the range of finite deformation. Hence, as for the local deformation, the detailed measurements have not been carried out yet in our previous study. So, in this paper, the local deformations generated under uniaxial tension and simple shear are investigated as the fundamental research. Especially, the progress of local deformations is revealed by comparing the measured values of upper and middle positions in the specimen.

Poroelasticity During Fluid Injection in Confined Geological Reservoirs: Incorporating Effects of Seal-Rock Stiffness

SPE Journal ◽  
2016 ◽  
Vol 22 (01) ◽  
pp. 184-197 ◽  
Author(s):  
K. Atefi Monfared ◽  
L.. Rothenburg
Keyword(s):  
Diffusion Constant ◽  
Vertical Component ◽  
Analytical Description ◽  
Pressure Change ◽  
Fluid Injection ◽  
Winkler Model ◽  
Realistic Assessment ◽  
Strain Components ◽  
Vertical Restraint ◽  
Fully Coupled

Summary This paper presents a new poroelastic solution to describe the time-dependent response of a confined geological reservoir to fluid injection through a fully penetrating vertical well treated as a point source. Unlike previous studies, vertical-confinement effects of seal rocks are incorporated in the solution. To facilitate analytical description of a fully coupled poroelastic behavior within the reservoir, the stiffness of surrounding rocks is described by the Winkler model, simplifying the response of seal rocks in the direction perpendicular to the reservoir plane. Analytical expressions are obtained for axisymmetric stress and strain components in the reservoir and for the vertical reaction stress. The latter is essential for evaluation of integrity of seal rocks during injection. Solutions are also obtained for the magnitude and location of the maximum-induced radial displacement as a function of time during injection. The effects of poroelastic coupling are articulated through the equivalent diffusion constant of the reservoir-seal rocks system. The latter is expressed through traditional poroelastic parameters as well as the relative stiffness of reservoir and seal rocks. The Winkler modulus of seal rocks, which is involved in all analytical relationships presented in this paper, is empirically linked to elastic characteristics of surrounding strata by comparing their response with the same pressure change in the reservoir according to the ideally elastic and Winkler models. The derived solutions are compared with previous studies, and verified against fully coupled numerical simulations. A comprehensive sensitivity analysis is conducted to assess the effects of the stiffness of the confining strata on the response of a uniform reservoir to injection. The vertical component of stress and the radial and vertical displacements are found to be substantially sensitive to the magnitude of the vertical restraint. The findings note the significance of incorporating seal-rock characteristics to attain a realistic assessment of the geomechanics of injection, specifically in formations with lower elastic moduli.

scholarly journals Spheroidal free periods of the earth observed at eight stations around the world

1964 ◽  
Vol 54 (2) ◽  
pp. 755-776
Author(s):  
L. E. Alsop
Keyword(s):  
Phase Velocity ◽  
Rayleigh Waves ◽  
Vertical Motion ◽  
Present Theory ◽  
Period Range ◽  
Moving Source ◽  
The Earth ◽  
Spectral Peaks ◽  
The World ◽  
Different Parts

ABSTRACT Spectral peaks corresponding to the spheroidal free periods of oscillation of the earth exist in the spectra of eight seismograms written at stations in different parts of the world shortly after the great Chilean earthquake of 22 May 1960. These data have been combined with those previously reported by various authors to obtain a very precise phase velocity vs period curve for Rayleigh waves in the period range of 200 to 3200 seconds. The observed spectral amplitudes lend some support to the assumption of a moving source, but they also indicate that the present theory is not adequate. The vertical motion is found to be symmetric with respect to reflections through the pole.

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.

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.

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