Crustal dilatancy and geomagnetic variations of short period.

Rikitake, Tsuneji

doi:10.5636/jgg.28.145

Cited by 18 publications

(15 citation statements)

References 16 publications

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“…Therefore we will not consider such sources here, although under special circumstances (e.g. the geometry of local conductivity changes) they may produce anomalies of substantial magnitude [Honkura and Kubo, 1986;Merzer and Klemperer, 1997;Rikitake, 1976aRikitake, , 1976b.…”

Section: Sources Of the Electromagnetic Fieldmentioning

confidence: 99%

“…Such phenomena have been discussed in several monographs and reviews [Gokhberg et al, 1995;Hayakawa and Fujinawa, 1994;Johnston, 1989Johnston, , 1997Lighthill, 1996;Park, 1996;Park et al, 1993;Rikitake, 1976aRikitake, , 1976b. We wish to describe briefly a scenario for them based on 1) analysis of experimental field and laboratory data and 2) modeling of electromagnetic emission which incorporates a mechanical model for pre-seismic deformation developed by us over the past fifteen years [Dobrovolsky et al, 1989;Gershenzon, 1992;Gershenzon and Gokhberg, 1989Gershenzon et al, 1986Gershenzon et al, , 1987Gershenzon et al, , 1989aGershenzon et al, , 1989bGershenzon et al, , 1990Grigoryev et al, 1989;Wolfe et al, 1996].…”

Section: Introductionmentioning

confidence: 99%

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Modeling of seismo-electromagnetic phenomena

Gershenzon¹,

Bambakidis²

2001

Russ. J. Earth Sci.

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Abstract.A model for seismo-electromagnetic (SEM) phenomena is described. The electromagnetic signals generated by mechanical disturbances in the earths crust have been calculated and compared with reported seismo-electromagnetic signals (SEMS). The major known SEM phenomena, namely, tectonomagnetic variations, electrotelluric anomalies, geomagnetic variations in the ultra-low frequency range and electromagnetic emission in the radio frequency range, have been considered. We have calculated the spectral densities associated with various types of sources. The set of formulas necessary to calculate the detected (filtered and averaged) electric and magnetic fields generated by mechanical disturbances for a wide range of frequencies and at various distances from the source are presented. Based on these formulas, we discuss the conditions under which electrokinetic, piezomagnetic and piezolectric effects could be responsible for SEMS. A comparison of estimated values of SEMS with reported field measurements leads to the conclusion that the sources of most anomalous SEMS are relatively close to the detector. In other words, the source of the signal is local, although the source of the mechanical disturbance which activates it, i.e. the epicenter of an earthquake, may be far away. Recommendations for field experiments (appropriate detector sitting, detector parameters and frequency range) following from the model developed here are presented.

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Section: Sources Of the Electromagnetic Fieldmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling of seismo-electromagnetic phenomena

Gershenzon¹,

Bambakidis²

2001

Russ. J. Earth Sci.

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“…However, the approximation of steady currents does not hold good and the theory described in this paper is no longer applicable. Electromagnetic induction must be fully taken into account as was discussed in detail by RIKITAKE (1976 …”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

“…RIKITAKE (1976) numerically investigated electromagnetic response in the crust with a resistivity anomaly as caused by dilatancy and suggested a possibility of detecting changes in the magnetic field observed on the earth's surface. In fact, changes in the ratio of the vertical to the horizontal components of geomagnetic variations have been reported to have taken place in association with the occurrence of earthquakes (YANAGIHARA, 1972;MIYA-KOSHI, 1975).…”

Section: Introductionmentioning

confidence: 99%

Perturbation of the electric current by a resistivity anomaly and its application to earthquake prediction.

Honkura

1976

J. geomagn. geoelec

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Perturbation of the steady current by a spherical resistivity anomaly embedded in a uniform medium is investigated for three typical models representing an anomalous area caused by dilatancy in the crust. The current is spatially uniform for one model and approximately uniform in the vicinity of the anomaly for other ones. Changes in amplitude and direction of the electric field seem to be observable at measuring sites near the anomalous area if the area is located very close to the earth's surface. The results are applicable to the electric field induced in the crust by fluctuations of the geomagnetic field if the period of variations is not very rapid so that the induced electric field can be treated as a uniform one in the upper crust. Thus a possibility of detecting changes in resistivity associated with shallow earthquakes by measuring the magnetotelluric fields is suggested from a theoretical consideration.

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“…This is in fact a difficult spectral range to record instrumentally. Rikitake (1976a) modelled electromagnetic induction in a 2-D rectangular conductor taken to represent a dilatant region in the Earth's crust. Using the appropriate induction parameters it was found that, for the particular model studied, enhancements of the horizontal field of up to 100% might be expected for short period (< 100 s) events.…”

Section: Frequency Contentmentioning

confidence: 99%

The time-dependence of electromagnetic response functions

Beamish¹

1982

Geophysical Surveys

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Abstract. Dynamic processes within the Earth axe capable of modifying many of its physical properties. This review considers the modification of electrical resistivity mainly by time-changes in the stressfield experienced by crustal materials. Laboratory experiments indicate that certain rock types, whose resistivity is controlled by the volume and geometry of microcracks, can undergo large resistivity variations in response to the typical strain accumulation and release that accompanies major earthquakes. Electromagnetic response functions axe reviewed with regard to their ability to monitor timechanges of resistivity in active regions. Some examples of the different experimental techniques used to investigate precursory changes in response functions prior to earthquakes are noted. The problems and successes of the subsequent correlation and interpretation of the derived response as a function of time are then discussed. Only relatively few controlled and integrated studies of time-dependent electromagnetic response functions exist. Those which are available, however, emphasise that changing stress-differentials occurring before major earthquakes can be monitored using suitable electromagnetic techniques.

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Crustal dilatancy and geomagnetic variations of short period.

Cited by 18 publications

References 16 publications

Modeling of seismo-electromagnetic phenomena

Modeling of seismo-electromagnetic phenomena

Perturbation of the electric current by a resistivity anomaly and its application to earthquake prediction.

The time-dependence of electromagnetic response functions

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