The tectonic stress and tectonic motion direction in the Pacific and Adjacent areas as calculated from earthquake fault plane solutions

1965 ◽  
Vol 55 (1) ◽  
pp. 147-152 ◽  
Author(s):  
A. E. Scheidegger
Keyword(s):  
Fault Plane ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Pacific Basin ◽  
Motion Direction ◽  
Fault Plane Solutions ◽  
Earthquake Fault ◽  
The Pacific ◽  
Tectonic Motion ◽  
Consistent Picture

Abstract The best P and T axes as well as the best normals to the null directions were calculated for groups of earthquake fault plane solutions belonging to 29 areas of the Pacific Basin and vicinity. The method employed was one developed in an earlier paper of the writer; it is based on a calculation of the eigenvectors of a quadratic form. It is shown that the principal horizontal stress (PHS) directions obtained in this fashion are in excellent agreement with those obtained from other evidence. In the Western Pacific Basin and vicinity the calculations were sufficiently dense to determine PHS trajectories; the latter are shown and yield a consistent picture of the area in question.

The tectonic stress and tectonic motion direction in Europe and Western Asia as calculated from earthquake fault plane solutions

1964 ◽  
Vol 54 (5A) ◽  
pp. 1519-1528 ◽  
Author(s):  
A. E. Scheidegger
Keyword(s):  
Fault Plane ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Motion Direction ◽  
Fault Plane Solutions ◽  
Plane Normal ◽  
Western Asia ◽  
Best Fitting ◽  
Tectonic Motion ◽  
Vector Sum

Abstract The statistics of fault plane solutions of earthquakes is further analyzed and it is shown that, to find a best axis or best plane to a set of axes, the eigenvectors of a certain matrix must be calculated. The justification for this procedure follows from the same argument as that of Fisher who showed that the best of a series of directions is obtained by forming the vector sum. The eigenvector technique is then applied to the pertinent axes of fault plane solutions of earthquakes that occurred in Europe and Western Asia. It is shown that, in this region, the focal mechanisms of the earthquakes tend to orient themselves in such a fashion that the P axes coincide with the principal horizontal stress directions, the latter being normal to the geographically prominent features. The null axes tend to lie in a plane normal to the best fitting P axes. The chief random element enters into the orientation of the T axes. All this is in conformity with the predictions of theory.

scholarly journals Seismic evidence for the tectonics of Central and Western Asia

1959 ◽  
Vol 49 (4) ◽  
pp. 369-378
Author(s):  
A. E. Scheidegger
Keyword(s):  
Fault Plane ◽  
Stress System ◽  
Motion Direction ◽  
Fault Plane Solutions ◽  
Small Areas ◽  
Mountain Ranges ◽  
Central Asian ◽  
Western Asia ◽  
Tectonic Motion

Abstract A statistical analysis of the null axes of the fault-plane solutions of earthquakes in any one area permits determination of the average tectonic motion direction of that area. In the present paper this method has been applied to areas in central and western Asia for which several hundred fault-plane solutions are readily available in the literature. The investigation yields the result that (seismically) calculated tectonic motion directions in a series of small areas that are part of a larger unit are consistent with each other and that there is in every case an excellent correlation with the tectonic motion of the area as postulated from geological studies. This appears to justify completely the seismic method. The seismically determined tectonic motion in central Asia appears to be mainly in a north-south direction. The motion refers to the present time (since the earthquakes occur at the present time), but it is the same as that postulated in geology for an explanation of the folding of the central Asian mountain ranges. This demonstrates that the stress system which created the central Asian mountains is active at the present time.

An eigenvalue method for the statistical evaluation of fault plane solutions of earthquakes

1963 ◽  
Vol 53 (4) ◽  
pp. 811-816 ◽  
Author(s):  
H. D. Fara ◽  
A. E. Scheidegger
Keyword(s):  
Input Data ◽  
Fault Plane ◽  
Test Case ◽  
Eigenvalues And Eigenvectors ◽  
Motion Direction ◽  
Fault Plane Solutions ◽  
A Value ◽  
Eigenvalue Method ◽  
Tectonic Motion ◽  
First Time

Abstract A method for the calculation of the tectonic motion direction in an area from fault plane solutions of earthquakes is presented. This method is similar to an earlier one described in the literature, but with an improved weighting procedure of the input data. The problem then reduces to that of calculating the eigenvalues and eigenvectors of a certain matrix. The new method enables one for the first time to get easily a value for the scattering of the input data. The method is first applied to a test case, and then to a series of earthquakes that occurred in the vicinity of the Marianas Islands.

Determining contemporary stress directions from neotectonic joint systems

1991 ◽  
Vol 337 (1645) ◽  
pp. 29-40 ◽  
Keyword(s):  
Stress Field ◽  
Fault Plane ◽  
Horizontal Stress ◽  
Tectonic Stress ◽  
Stress Fields ◽  
Ebro Basin ◽  
Fault Plane Solutions ◽  
Near Surface ◽  
Initiation And Propagation

A neotectonic joint is a crack which propagated in a tectonic stress field that has persisted with little or no change of orientation until the present day. Investigating neotectonic joints is of value because the approximate orientation of the contemporary stress field can be inferred from them. Although exposed neotectonic joints in the flat-lying sedimentary rocks of some cratons are related to regional stress fields, their initiation and propagation occurred close to the Earth’s surface. For example, neotectonic joints in the centre of the Ebro basin (N. Spain) preferentially developed in a thin, near-surface channel sited within a sequence of weak Miocene limestones underlying the upper levels of plateaux. The Ebro basin joints strike uniformly NNW-SSE throughout an area of at least 10 000 km 2 and they are parallel or subparallel to the direction of greatest horizontal stress extrapolated from in situ stress measurements and fault-plane solutions of earthquakes.

THE CONTINENTAL ACCRETION AND FOLDING OF AUSTRALIA BY PACIFIC SEA FLOOR UNDERSPREADING

1972 ◽  
Vol 12 (2) ◽  
pp. 70
Author(s):  
A.C.M. Laing
Keyword(s):  
Solar System ◽  
Liquid Core ◽  
Continental Drift ◽  
Horizontal Stress ◽  
The Other ◽  
Pacific Basin ◽  
Sea Floor ◽  
The Earth ◽  
The Pacific ◽  
Continental Accretion

The theory of continental drift is criticised for being based on a number of fallacies.The fallacies discussed include polar wandering and Permian glaciation in Australia. Both are regarded as nonexistent. Data are presented to indicate firstly that Australia has grown by continental accretion and secondly that this growth has taken place under a horizontal stress directed outwards from the Pacific Basin. It is postulated that this horizontal stress is caused by a gradually intensifying bump in the liquid core of the earth, which is believed to have formed in the condensation and accretion stage of the solar system, mainly from two lumps of different composition and properties, one now constituting the Pacific Basin, the other the remainder of the Earth.A corollary to this hypothesis is that the structural equivalents of the petroliferous basins of North America lie under the Tasman, Coral, and Timor seas.

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