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

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.

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

Bulletin of the Seismological Society of America ◽

10.1785/bssa0590020503 ◽

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.

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3D Structure of Striations in the North Pacific

Journal of Physical Oceanography ◽

10.1175/jpo-d-21-0076.1 ◽

2021 ◽

Author(s):

YU ZHANG ◽

YU PING GUAN ◽

RUI XIN HUANG

Keyword(s):

North Pacific ◽

3D Structure ◽

Three Dimensional ◽

Vertical Plane ◽

Dimensional Structure ◽

The North ◽

Layer Analysis ◽

Fluid Potential ◽

The North Pacific

AbstractOcean striations are composed of alternating quasi-zonal band-like flows; this kind of organized structure of currents be found in all world’s oceans and seas. Previous studies have mainly been focused on the mechanisms of their generation and propagation. This study uses the spatial high-pass filtering to obtain the three-dimensional structure of ocean striations in the North Pacific in both the z-coordinate and σ-coordinate based on 10-yr averaged SODA3 data. First, we identify an ideal-fluid potential density domain where the striations are undisturbed by the surface forcing and boundary effects. Second, using the isopycnal layer analysis, we show that on isopycnal surfaces the orientations of striations nearly follow the potential vorticity (PV) contours, while in the meridional-vertical plane the central positions of striations are generally aligned with the latitude of zero gradient of the relative PV. Our analysis provides a simple dynamical interpretation and better understanding for the role of ocean striations.

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S waves: Alaska and other earthquakes

Bulletin of the Seismological Society of America ◽

10.1785/bssa0500040581 ◽

1960 ◽

Vol 50 (4) ◽

pp. 581-597 ◽

Cited By ~ 1

Author(s):

William Stauder

Keyword(s):

Focal Mechanism ◽

Fault Plane ◽

P Wave ◽

Wave Analysis ◽

Point Model ◽

S Wave ◽

S Waves ◽

Wave Solutions ◽

Single Force

ABSTRACT Techniques of S wave analysis are used to investigate the focal mechanism of four earthquakes. In all cases the results of the S wave analysis agree with previously determined P wave solutions and conform to a dipole with moment or single couple as the point model of the focus. Further, the data from S waves select one of the two nodal planes of P as the fault plane. Small errors in the determination of the angle of polarization of S are shown to result in scatter in the data of a peculiar character which might lead to misinterpretation. The same methods of analysis which in the present instances show excellent agreement with a dipole with moment source are the methods which in a previous paper required a single force type mechanism for a different group of earthquakes.

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S-wave studies of earthquakes of the North Pacific, Part II: Aleutian Islands

Bulletin of the Seismological Society of America ◽

10.1785/bssa0530010059 ◽

1963 ◽

Vol 53 (1) ◽

pp. 59-77

Author(s):

William Stauder ◽

Agustin Udias

Keyword(s):

Aleutian Islands ◽

Aleutian Island ◽

Stress System ◽

S Wave ◽

The North ◽

Double Couple ◽

First Motion ◽

Good Determination ◽

The North Pacific

Abstract The polarization of the S wave at stations distributed azimuthally about the source is examined for each of twenty-five Aleutian Island earthquakes. A combination of data from the first motion of P and from the polarization of S is then used to study the focal mechanisms of the earthquakes. This combination of P and S wave data is found to make possible a good determination of the focal mechanism in cases where data from the first motion of P alone do not suffice. The earthquakes are divided into three groups according to three basic patterns of S wave polarization. The first group (fourteen earthquakes) corresponds to a double couple. The second group (five earthquakes) and the third group (six earthquakes) are conformable to conjugate shears and may therefore be explained by single couple sources of opposite moment, respectively. It is shown that a uniform principal stress system predominates in the region and that the axis of greatest compressive stress is normal to the trend of the island arc.

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