Piezomagnetic fields produced by dislocation sources
- Univ. of Tokyo (Japan)
Tectonomagnetic modeling based on the linear piezomagnetic effect is reviewed with special attention to dislocation models. Stacey's scheme was the prototype for such modeling, as proposed in his seismomagnetic calculations in 1964. The linear piezomagnetic law is presented, in which the stress-induced magnetization is expressed as a linear combination of stress components. The Gauss law for magnetic field and the Cauchy-Navier equation for static elastic equilibrium are combined through linear piezomagnetism and the Hooke law to yield the basic equation for piezomagnetic potential. A representation theorem for its solution is given by surface integrals of the displacement and its normal derivative over the strained body. A Green's function method is developed to compute the piezomagnetic field produced by a dislocation surface in an elastic half-space. Volterra's formula for piezomagnetic potential is derived by modifying Stacey's scheme for tectonomagnetic modeling. The Green's functions for the problem are called elementary piezomagnetic potentials, which are potentials produced by elementary dislocations. Special consideration is required to construct the elementary piezomagnetic potentials because the stress field around a point dislocation has a singularity of order r[sup [minus]3]. The integral representing elementary piezomagnetic potentials is not uniformly convergent. Owing to inappropriate convergency, the Green's functions obtained in an earlier study led to a puzzling outcome. Revised Green's functions give consistent results with those obtained so far by numerical integrations. Generally the piezomagnetic field produced by dislocation sources is weak in the case of a homogeneous earth model. Two enhancement effects for piezomagnetic signals are suggested: one due to inhomogeneous magnetization and the other via bore-hole observations. 53 refs., 6 figs.
- OSTI ID:
- 7140768
- Journal Information:
- Surveys in Geophysics; (Switzerland), Journal Name: Surveys in Geophysics; (Switzerland) Vol. 15:4; ISSN SUGEEC; ISSN 0169-3298
- Country of Publication:
- United States
- Language:
- English
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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
EARTH PLANET
EQUATIONS
FLUID MECHANICS
FUNCTIONS
GEOPHYSICS
GREEN FUNCTION
HYDRODYNAMICS
INTEGRAL EQUATIONS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MECHANICS
PLANETS
SEISMOLOGY
TECTONICS
VOLTERRA INTEGRAL EQUATIONS