The S-wave project for focal mechanism studies, earthquakes of 1963

1966 ◽  
Vol 56 (6) ◽  
pp. 1363-1371 ◽  
Author(s):  
William Stauder ◽  
G. A. Bollinger
Keyword(s):  
Point Source ◽  
Focal Mechanism ◽  
Computer Method ◽  
Couple Model ◽  
S Wave ◽  
Wave Data ◽  
Kurile Islands ◽  
Equivalent Point ◽  
Double Couple

Abstract P- and S-wave data for thirty-five earthquakes selected from among the larger earthquakes of 1963 have been investigated. Focal mechanism determinations for twenty-six of these shocks are here presented. The solutions are based upon a combination of a graphical and a computer method for determining the poles of the nodal planes. In all cases it has been found that the mechanism may be adequately represented by a double couple as an equivalent point source of the focus, although in some few instances a single couple cannot be excluded as a possible alternate interpretation. The solution of a mid-Atlantic earthquake of November 17, 1963 is presented as an example of a focus which clearly conforms to the double couple model. Special attention is called to the solutions for a series of earthquakes in the Kurile Islands, and to three earthquakes of the mid-Atlantic.

Application of numerical method for S-wave focal mechanism determinations to earthquakes of Kamchatka-Kurile Islands Region

1964 ◽  
Vol 54 (6A) ◽  
pp. 2049-2065 ◽  
Author(s):  
Agustin Udias ◽  
William Stauder
Keyword(s):  
Focal Mechanism ◽  
Least Squares Method ◽  
S Wave ◽  
Regional Trend ◽  
Thrust Faulting ◽  
Kurile Islands ◽  
Continental Block ◽  
Principal Axes ◽  
Double Couple

abstract The least squares method for the determination of focal mechanism using S-wave data developed by Udias (1964) has been applied to 34 earthquakes of the Kamchatka-Kurile Islands Regions. For most of the earthquakes studied the source mechanism was found to conform best to a double couple model. The accuracy and stability of the solutions are examined. The direction of the principal axes of stress for most of the solutions show a steeply dipping axis of tension and an almost horizontal axis of pressure. The orientation of the pressure axes is normal to the regional trend. The direction of the stresses suggest a thrust faulting with predominantly dip slip motions such that the continental block moves over the oceanic.

A computer program for focal mechanism determination combining P and S wave data

1969 ◽  
Vol 59 (2) ◽  
pp. 503-519
Author(s):  
Agustin Udias ◽  
Dieter Baumann
Keyword(s):  
Computer Program ◽  
Focal Mechanism ◽  
Total Error ◽  
Source Model ◽  
Polarization Angle ◽  
S Wave ◽  
Period Range ◽  
S Waves ◽  
Double Couple ◽  
The Relationship

abstract A computer program has been developed to find the orientation of a double couple source model for the mechanism of an earthquake which best satisfies the data from P and S waves. The relationship between the two axes of the solution given by the equations for the polarization angle of S is used in order to rapidly find the orientation of the source model for which a total error value involving the error of S and P data is a minimum. The program gives best results for data from homogeneous instruments of similar period range. Solutions for three earthquakes, selected because of the orientation of the source, are presented and the reliability of their solutions under ideal conditions is discussed.

Combination of P and S data for the determination of earthquake focal mechanism

1971 ◽  
Vol 61 (6) ◽  
pp. 1655-1673 ◽  
Author(s):  
Umesh Chandra
Keyword(s):  
Focal Mechanism ◽  
P Wave ◽  
Wave Polarization ◽  
S Wave ◽  
Polarization Data ◽  
Wave Data ◽  
Earthquake Focal Mechanism ◽  
First Motion ◽  
Depth Ranges

abstract A method has been proposed for the combination of P-wave first-motion directions and S-wave polarization data for the numerical determination of earthquake focal mechanism. The method takes into account the influence of nearness of stations with inconsistent P-wave polarity observations, with respect to the assumed nodal planes. The mechanism solutions for six earthquakes selected from different geographic locations and depth ranges have been determined. Equal area projections of the nodal planes together with the P-wave first-motion and S-wave polarization data are presented for each earthquake. The quality of resolution of nodal plane determination on the basis of P-wave data, S-wave polarization, and the combination of P and S-wave data according to the present method, is discussed.

Focal mechanism of the Prince William Sound, Alaska earthquake of March 28, 1964

1969 ◽  
Vol 59 (2) ◽  
pp. 799-811
Author(s):  
Samuel T. Harding ◽  
S. T. Algermissen
Keyword(s):  
Focal Mechanism ◽  
P Wave ◽  
Type I ◽  
Type Ii ◽  
Prince William Sound ◽  
Wave Polarization ◽  
S Wave ◽  
Polarization Data ◽  
Wave Data ◽  
First Motion

abstract Two nodal planes for P were determined using a combination of P-wave first motion and S-wave polarization data and from S-wave data alone. The S-wave polarization error, δ∈, is slightly lower for a type Il than for a type I mechanism. The type I mechanism solution indicates a predominately dip-slip faulting on a steeply dipping plane. The preferred solution is a type II mechanism with the following P nodal planes: strike N62°E, dip 82°S, (a plane); strike N22°W, dip 52°W, (b plane). Two solutions are possible: right lateral faulting which strikes northeast; or, left lateral faulting which strikes northwest. Both possible fault planes dip steeply.

The use of ScS-wave data in focal mechanism determinations

1962 ◽  
Vol 52 (3) ◽  
pp. 551-572
Author(s):  
Augustine S. Furumoto
Keyword(s):  
Focal Mechanism ◽  
Quantitative Relationship ◽  
P Wave ◽  
Wave Method ◽  
S Wave ◽  
Focal Mechanism Solutions ◽  
Wave Data

abstract In this paper the S wave method of focal mechanism determination is extended to include the ScS wave. By the establishment of the quantitative relationship between the directions of vibration of the S and the ScS, ScS wave data can be reduced to a form of S wave data usable for focal mechanism determinations. The new extension has been checked by reobtaining focal mechanism solutions for four heartquakes using ScS wave data. Results were consistent with previous solutions by the S wave method or P wave method.

S-Wave studies of earthquakes of the North Pacific, Part I: Kamchatka

1962 ◽  
Vol 52 (3) ◽  
pp. 527-550 ◽  
Author(s):  
William Stauder
Keyword(s):  
Focal Mechanism ◽  
North Pacific ◽  
Vertical Plane ◽  
Point Model ◽  
S Wave ◽  
S Waves ◽  
The North ◽  
Plane Normal ◽  
Double Couple ◽  
The North Pacific

abstract The polarization of S waves at stations distributed azimuthally about the source is examined for each of twenty-three Kamchatka earthquakes of 1950-1960. In nineteen of these earthquakes the P and S wave data are in agreement with a double couple source as the point model of the focal mechanism. The S waves indicate a uniform mechanism which repeats itself from earthquake to earthquake and from which it may be inferred that the axes of greatest and least stress at the foci tend to lie in a vertical plane normal to the trend of the Kamchatka-Kuriles arc. The axis of least stress usually plunges almost vertically under the continent, but may also plunge less steeply, at angles as low as 45 degrees. At least two earthquakes may be represented by a single couple source.

Direct shear-wave seismic survey in Sanhu area, Qaidam Basin, west China

2022 ◽  
Vol 41 (1) ◽  
pp. 47-53
Author(s):  
Zhiwen Deng ◽  
Rui Zhang ◽  
Liang Gou ◽  
Shaohua Zhang ◽  
Yuanyuan Yue ◽  
...  
Keyword(s):  
Shear Wave ◽  
Reservoir Characterization ◽  
Qaidam Basin ◽  
P Wave ◽  
Data Sets ◽  
Direct Shear ◽  
Subsurface Structure ◽  
S Wave ◽  
West China ◽  
Wave Data

The formation containing shallow gas clouds poses a major challenge for conventional P-wave seismic surveys in the Sanhu area, Qaidam Basin, west China, as it dramatically attenuates seismic P-waves, resulting in high uncertainty in the subsurface structure and complexity in reservoir characterization. To address this issue, we proposed a workflow of direct shear-wave seismic (S-S) surveys. This is because the shear wave is not significantly affected by the pore fluid. Our workflow includes acquisition, processing, and interpretation in calibration with conventional P-wave seismic data to obtain improved subsurface structure images and reservoir characterization. To procure a good S-wave seismic image, several key techniques were applied: (1) a newly developed S-wave vibrator, one of the most powerful such vibrators in the world, was used to send a strong S-wave into the subsurface; (2) the acquired 9C S-S data sets initially were rotated into SH-SH and SV-SV components and subsequently were rotated into fast and slow S-wave components; and (3) a surface-wave inversion technique was applied to obtain the near-surface shear-wave velocity, used for static correction. As expected, the S-wave data were not affected by the gas clouds. This allowed us to map the subsurface structures with stronger confidence than with the P-wave data. Such S-wave data materialize into similar frequency spectra as P-wave data with a better signal-to-noise ratio. Seismic attributes were also applied to the S-wave data sets. This resulted in clearly visible geologic features that were invisible in the P-wave data.

A least squares method for earthquake mechanism determination using S-wave data

1964 ◽  
Vol 54 (6A) ◽  
pp. 2037-2047
Author(s):  
Agustin Udias
Keyword(s):  
Least Squares ◽  
Statistical Evaluation ◽  
Least Squares Method ◽  
Numerical Approach ◽  
Focal Mechanisms ◽  
Least Square ◽  
S Wave ◽  
Double Couple ◽  
Earthquake Mechanism

abstract In this paper a numerical approach to the determination of focal mechanisms based on the observation of the polarization of the S wave at N stations is presented. Least-square methods are developed for the determination of the orientation of the single and double couple sources. The methods allow a statistical evaluation of the data and of the accuracy of the solutions.

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