Geoscience Reference
In-Depth Information
along the already existing faults. During this process the friction between rocks
and the release of gases caught inside rocks causes increase in temperature. The
heat, water vapor and gas reach the Earth's surface and as a result the litho-
atmospheric coupling starts. First, convective heat flux (hot water and gas) changes
the temperature of the Earth's surface. Second, changes of the water level with
usual temperature lead to alterations in soil moisture, and consequently the
physical properties of the soil (Israel and Bjornsson
1966
; King
1980
; King et al.
1996
; Immè et al.
2006
; Giammanco et al.
2007
; Giammanco and Bonfanti
2009
).
The difference in physical properties determines the different temperatures on the
surface. Third is the greenhouse effect, when the optically active gases are escaped
to the surface (Tronin et al.
2004
).
The anomalies in heat and related phenomena occur in a vast area. Remote
sensing techniques provide the opportunity of studying the consequences of
seismic activities in large scales. However, other non-seismic factors like surface
formation type and characteristics, seasonal changes, solar radiation, etc. may be
affecting the temperature regime of an earthquake prone region. The heat gener-
ated by the chemical and physical processes inside the earth's ground may not be
high enough to be distinguished from background noise. Nevertheless, the resul-
tant phenomena like air humidity are found to be increased by the earthquake
related energy release.
The idea that the thermal anomalies may be connected with seismic activity
was put to application in Russia, China and Japan. In 1980, Russian researchers
detected thermal anomalies prior to an earthquake in central Asia using satellite
images. After that, thermal anomaly in surface temperature has been observed
around 1-14 days before many strong earthquakes instances with abrupt change in
the temperature value of the order of 3-7 C or more and disappeared a few days
after the main events (Gorny et al.
1988
; Qiang et al.
1999
; Tronin
2000
; Tronin
et al.
2002
; Ouzounov and Freund
2004
; Saraf and Choudhury
2005a
,
b
,
c
;
Choudhury et al.
2006
; Genzano et al.
2007
; Ma et al.
2008
,
2010
). Some remote
sensing satellites can measure the radiations coming from the earth in thermal
bands and provide useful information prior to earthquakes. Due to their suitable
temporal and spatial resolutions, the thermal infrared bands of Advanced Very
High
Resolution
Radiometer
(AVHRR)
and
Moderate
Resolution
Imaging
Spectroradiometer (MODIS) data can be used (Revathi et al.
2011
).
Amount of water vapor in the atmosphere in a region is highly related to the
speed of evaporation. Under stable conditions of water supply this factor is mainly
proportional to the temperature. So changes in SLHF are controlled by variation in
surface temperature, which is believed to be a precursory parameter during an
earthquake. However topography, feature type, solar radiation, weather, seasonal
changes and many non-shock factors can affect the temperature in a large area and
some causes, such as human or construction activities may also influence on the
temperature of a small area (Tronin
2000
; Liu et al.
2007
). Relationships between
inland and oceanic seismic activities and anomalous changes in SLHF in different
parts of the world have been registered by many researchers. Time series of SLHF
have shown meaningful rises from a month to few days before the earthquake
