Rotational motions in homogeneous anisotropic elastic media

Nguyen Dinh Pham; Heiner Igel; Josep de la Puente; Martin Käser; Michael A. Schoenberg

doi:10.1190/1.3479489

Rotational motions in homogeneous anisotropic elastic media

Geophysics ◽

10.1190/1.3479489 ◽

2010 ◽

Vol 75 (5) ◽

pp. D47-D56 ◽

Cited By ~ 11

Author(s):

Nguyen Dinh Pham ◽

Heiner Igel ◽

Josep de la Puente ◽

Martin Käser ◽

Michael A. Schoenberg

Keyword(s):

Rotational Energy ◽

Propagation Direction ◽

Body Waves ◽

Elastic Media ◽

P Waves ◽

Rotation Rates ◽

Isotropic Media ◽

Christoffel Equation ◽

Rotational Motions ◽

Anisotropic Elastic

Rotational motions in homogeneous anisotropic elastic media are studied under the assumption of plane wave propagation. The main goal is to investigate the influences of anisotropy in the behavior of the rotational wavefield. The focus is on P-waves that theoretically do not generate rotational motion in isotropic media. By using the Kelvin–Christoffel equation, expressions are obtained of the rotational motions of body waves as a function of the propagation direction and the coefficients of the elastic modulus matrix. As a result, the amplitudes of the rotation rates and their radiation patterns are quantified and it is concluded that (1) for strong local earthquakes and typical reservoir situations quasi P-rotation rates induced by anisotropy are significant, recordable, and can be used for inverse problems; and (2) for teleseismic wavefields, anisotropic effects are unlikely to be responsible for the observed rotational energy in the P coda.

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The topological nature of the polarization field for body waves in anisotropic elastic media

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1980.0037 ◽

1980 ◽

Vol 370 (1742) ◽

pp. 331-350 ◽

Cited By ~ 11

Keyword(s):

Eigenvalue Problem ◽

Sound Wave ◽

Body Waves ◽

Polarization Field ◽

Elastic Media ◽

Wave Polarization ◽

Different Types ◽

Anisotropic Elastic ◽

Elastic Crystals

Topologically, two different types of sound wave polarization fields are possible in elastic crystals without acoustic axes. It is shown that only one type occurs. Usually, however, acoustic axes are present. The relation between the Khatkevich condition for acoustic axes and the discriminant of the eigenvalue problem is elucidated.

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Weak-contrast edge and vertex diffractions in anisotropic elastic media

Wave Motion ◽

10.1016/s0165-2125(98)00044-4 ◽

1999 ◽

Vol 29 (4) ◽

pp. 363-373 ◽

Cited By ~ 5

Author(s):

Martin Tygel ◽

Bjørn Ursin

Keyword(s):

Elastic Media ◽

Anisotropic Elastic

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Determination of the ray surface and recovery of elastic constants of anisotropic elastic media: a direct and inverse approach

Journal of Physics Condensed Matter ◽

10.1088/0953-8984/7/20/007 ◽

1995 ◽

Vol 7 (20) ◽

pp. 3863-3880 ◽

Cited By ~ 10

Author(s):

L Wang

Keyword(s):

Elastic Constants ◽

Elastic Media ◽

Inverse Approach ◽

Anisotropic Elastic

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Evidence of tectonic release from underground nuclear explosions in long-period P waves

Bulletin of the Seismological Society of America ◽

10.1785/bssa0730020593 ◽

1983 ◽

Vol 73 (2) ◽

pp. 593-613

Author(s):

Terry C. Wallace ◽

Donald V. Helmberger ◽

Gladys R. Engen

Keyword(s):

Upper Mantle ◽

High Stress ◽

Test Site ◽

Strike Slip ◽

Body Waves ◽

Release Time ◽

P Waves ◽

Underground Nuclear Explosions ◽

Nuclear Explosions ◽

Long Period

abstract In this paper, we study the long-period body waves at regional and upper mantle distances from large underground nuclear explosions at Pahute Mesa, Nevada Test Site. A comparison of the seismic records from neighboring explosions shows that the more recent events have much simpler waveforms than those of the earlier events. In fact, many of the early events produced waveforms which are very similar to those produced by shallow, moderate-size, strike-slip earthquakes; the phase sP is particularly obvious. The waveforms of these explosions can be modeled by assuming that the explosion is accompanied by tectonic release represented by a double couple. A clear example of this phenomenon is provided by a comparison of GREELEY (1966) and KASSERI (1975). These events are of similar yields and were detonated within 2 km of each other. The GREELEY records can be matched by simply adding synthetic waveforms appropriate for a shallow strike-slip earthquake to the KASSERI observations. The tectonic release for GREELEY has a moment of 5 ՠ1024 dyne-cm and is striking approximately 340°. The identification of the sP phase at upper mantle distances indicates that the source depth is 4 km or less. The tectonic release time function has a short duration (less than 1 sec). A comparison of these results with well-studied strike-slip earthquakes on the west coast and eastern Nevada indicate that, if tectonic release is triggered fault motion, then the tectonic release is relatively high stress drop, on the order of several hundred bars. It is possible to reduce these stress drops by a factor of 2 if the tectonic release is a driven fault; i.e., rupturing with the P velocity. The region in which the stress is released for a megaton event has a radius of about 4 km. Pahute Mesa events which are detonated within this radius of a previous explosion have a substantially reduced tectonic release.

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