Geoscience Reference
In-Depth Information
Chapter 11
Electromagnetic Effects Resulted
from Explosions
Abstract
In this chapter we study man-made low-frequency electromagnetic fields
resulted from high explosive or nuclear detonations. The main emphasis is on
underground explosion effects and a variety of accompanying electromagnetic
phenomena caused by rock deformation and perturbations of the Earth magnetic
field. We start with basic mechanisms for a so-called electromagnetic pulse (EMP)
occurring just after the detonation and belonging to ULF/ELF frequency range. It
is usually the case that the EMP precedes the co-seismic phenomena caused by
seismic wave arrival at the observation point. Then we examine the atmospheric
effects caused by the generation of dusty clouds and propagation of aerial shock
waves (SWs). In the remainder of this chapter we consider the perturbations of the
ionospheric plasma caused by an upward propagating SW.
Keywords
Aerial shock wave (SW) Electromagnetic pulse (EMP) Gas-dust
cloud Residual electromagnetic field Underground explosion
11.1
Diamagnetic Plasma Effect of Explosions
11.1.1
Observations of EMP Resulted from Underground
Explosions
The earliest detailed recordings of the EMP caused by underground tests have been
published after the series of nuclear detonations referred as Hardtack II on the
proving ground in Nevada in 1958 (Zablocki
1966
). At first the examination of
ground conductivity was planned in the vicinity of an underground explosion cham-
ber. However the strong low-frequency electric field was unexpectedly detected
at the moment of detonation. The electric pickup arising simultaneously with the
detonation was so high that it prevented seriously the recording of conductivity
changes. These findings lent impetus to a study of interrelationship between
electromagnetic and seismic effects because of importance of this research for the
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