Electromagnetic Effects Resulted from Natural Disasters - Ultra and Extremely Low Frequency Electromagnetic Fields - page 393

M S 1

S 2

Fig. 10.8 According to the model by Dudkin et al. ( 2010 ), the magnetic dipole vector M is on the
intersection line of polarization ellipse planes measured at two different ground-based station, S 1
and S 2

z 1

y 1

y

z

O 1 x 1

M
z 2

l 1

O

x

y 2

M

l 2

O 2

x 2

M

y

z z '

r 0

ʸ

p m

ʱ 1

Earthquake
focal zone

x

ʱ 2

Fig. 10.9 A sketch of equipment arrangement and the magnetic-dipole source location. The
reference magnetometer is located at the origin of coordinate system O, and the places of the
second and third magnetometers are shown by the vectors l 1 and l 2

Semi-empirical and semi-analytic techniques for finding the ULF source in
the background of natural noise have been reported by Surkov et al. ( 2004 ).
To distinguish a weak ULF source signal from the natural noise, a network of
multicomponent magnetometers is supposed to be used. A sketch of equipment
arrangement is shown in Fig. 10.9 . The distances between magnetometers are
designed such that j l 1 j , j l 2 j L, where L is the spatial scale of the variations
originated from the ionosphere-magnetosphere origin. The influence of these large-
scale variations can be eliminated by subtraction of data measured by a set