Geoscience Reference
In-Depth Information
of the Total Electron Content (TEC), observed days before major events suggest
the presence of a positive charge on the Earth's surface to which the ionosphere res-
ponds (Liperovsky et al., 2000; Liu et al., 2000, 2001; Naaman et al., 2001). A dis-
cussion of the pre-earthquake effects is found in Pulinets and Boyarchuk (2004) who
favor release of radon at the Earth's surface as the cause of the reported ionospheric
perturbations.
“Thermal Anomalies”
Non-stationary areas of enhanced infrared (IR) emission, linked to impending (Gornyi
et al., 1988; Qiang et al., 1990, 1991; Srivastav et al., 1997) with apparent land sur-
face temperature variations on the order of 2-4ºC. The effect has become known
as “thermal anomalies”. The cause has remained enigmatic (Ouzounov et al., 2007;
Srivastav et al., 1997; Tramutoli et al., 2005; Tronin, 2002, 2004). The rapidity of the
temperature variations rules out a flow of Joule heat from deep below. Several alter-
native processes have been invoked: Rising well water levels and changing moisture
contents in the soil; near-ground air ionization due to radon emission leading to the
condensation of water vapor and the release of latent heat; emanation of warm gases
(Gornyi et al., 1988), in particular of CO
2
(Quing et al., 1991; Tronin, 1999, 2002).
Other Pre-earthquake Signals
There are claims of other pre-earthquake phenomena such as differences in ground
potentials (Varotsos, 2005; Varotsos et al., 1993, 1986), low-lying fog and unusual
clouds (Tsukuda, 1997), and of course the rich folklore of abnormal animal behavior
(Tributsch, 1984).
Common Traits Among Non-seismic Pre-earthquake Signals
Many pre-earthquake signals require transient electric currents in the Earth's crust.
Electric currents arising from streaming potentials are well known (Bernabe, 1998;
Jouniaux et al., 2000; Merzer and Klemperer, 1997; Morrison et al., 1989). Currents
due to piezoelectric voltages generated in quartz-bearing rocks have been invoked to
explain pre-earthquake low-frequency EM emissions (Gershenzon and Bambakidis,
2001; Ogawa and Utada, 2000; Sasai, 1991). However, no consensus of opinion has
emerged.
EXPERIMENTAL
Important properties of rocks have been profoundly misunderstood or misinterpreted
in the past, specifically the electrical properties of igneous and high-grade metamor-
phic rocks, which make up the bulk of Earth's crust in the depth range where most
earthquakes occur, about 7-35 km.
At the root lies the fact that, in the geosciences, electrical conductivity of rocks
is typically, often exclusively discussed in terms of ionic conductivity (high tempera-
tures, partial melts) or electrolytical conductivity (low temperatures, fl uids). However,
from a solid state physics viewpoint there may be other mechanisms that can contrib-
ute signifi cantly. One of these mechanisms arises from the fact that not all oxygen
anions exist in their common 2-valence state but in the 1-valence state.
