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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS008 Oral Presentation 1999
Short and long range impact of seismoelectromagnetic effects
Dr. Farshed Karimov
Seismology Institute of Earthquake Engineering and Seismology IASPEI
Space-time development of seismotectonic process initiates space-time patterns of
seismoelectromagnetic effect (SME). There are different physical processes can take place in an
earthquake preparation zone. For instance deformation of earth crust solid phase, underground fluid
flow from locally stressed crust or opposite direction flow at dilatancy stage. As far as SME can be
generated both by solid phase deformation or underground fluid flow the character of SME pattern can
be diverse. If SME signal is radiating directly from the source solid deformed volume for instance by
virtue of piezoelectric or piezomagnetic effects one can detect the signal quite immediately at any
distance, limited by the discrimination level only. Its a case of long range SME effect. Such effect is
likely to be expected for rocks in the source with high enough piezoelectric or piezomagnetic properties.
For the underground flow SME radiation mechanism one can expect less or more shift in time
appearance of the signal, depending on site location within the source preparation zone or away from it.
Really it takes time for spreading of fluid flow within or out of the preparation zone. Electrokinetic
stream intensity is varying in space and time and therefore the SME signal turns up dependent on how
fluid flow is distributing and spreading. Its an example of short range SME effect. Such effect is likely to
be expected for the intensive enough underground fluid streams, high enough rocks zeta-potential, high
enough rocks porosity, low enough liquid viscosity and high underground fluid ion concentration. Such
delay can take place also for the ionosphere spreading of SME, carrying by electric currents. Mean term
tectonomagnetic effects of earthquake preparation observed in the seismic areas present a type of SME
effects. There are rocks with very low magnetization and piezomagnetic effects majoring in the
Tajikistan and one can scarcely expect sizable piezomagnetic origin of tectonomagnetic variations. In
contrast, there are wide spread porous rocks with underground liquids which can be regarded as an
electrolyte. Straight tectonomagnetic signal space-time shift has been observed as well during Nurek
reservoir water level seasonal variations up to 50 meters. The speed of underground water flow as
much as several kilometers per day, measured by means of bore holes, correlates with space-time shift
of the local tectonomagnetic effect in the vicinity of the water reservoir, featuring short range character
of that SME effect. Its principally possible that both impacts from long and short range effects will turn
up comparable at the same time as well. There should be special technique to separate each other.
Keywords: tectonomagnetism, piezomagnetism, electrokinetics