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Fig. 10.10
A volcanic lightning occurring during the Sakurajima volcano eruption in southern
Japan (NASA—March 11, 2013)
of Karymsky volcano (Rulenko
1979
). The measurements have shown that the hot
vapor contained positive charges. The electric field variations associated with steam
plumes from the geothermal well have been observed by Björnsson and Vonnegut
(
1965
).
Enhancement of ULF electromagnetic noise in the frequency bands of
0.01-0.6 Hz and 1.0-3.0 Hz has been detected several days before and after the
volcano eruption (Fujinawa et al.
1992
). It was hypothesized that this enhancement
can be due to the magma motion along the volcano vent that results in electrokinetic
effects in the rocks followed by the electromagnetic noise. It is also believed
that in the volcano regions there are a lot of underground cameras filled by
the fluid with pressure from the hydrostatic up to the lithostatic level (Johnston
1989
). The destruction of such cameras can generate electromagnetic signals in
the range of 0.01-100 Hz. We have estimated the electrokinetic effect when we
studied electromagnetic phenomena related to an EQ. Although this mechanism
can explain the observed anomalies, only rough estimates are available because
such important parameters as rock permeability, pore fluid pressure and etc.
vary in an extremely wide band. Additionally, tectonomagnetic, tectonoelectric,
magnetohydrodynamical, and other mechanisms are considered as possible causes
of the observed phenomena (Johnston
1997
; Uyeda et al.
2002
; Zlotnicki and
Nishida
2003
). The history of investigation for field volcanology including the
applied electromagnetic method such as resistivity sounding or self-potential and
geomagnetic field measurements are found in a review by Hashimoto (
2005
).
In the model by Kopytenko and Nikitina (
2004a
,
b
), the GMP caused by a
conducting magma upwelling along the volcano vent is treated as a possible source
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