Geoscience Reference
In-Depth Information
2 Earthquake Prediction
The basic concept of the classical approach to earthquake prediction, which was
suggested by Raid in 1910, is monitoring the places that have the previous records
of this event (Revathi et al.
2011
). Knowledge of the earthquake experiences,
tectonic setting, and geological characteristics of an area help determining the
locations and recurrence intervals of earthquakes (Nelson
2010
). By studying the
shake records of an area it will be possible to determine recurrence intervals of
major earthquakes. In fact, long-term prediction methods suggest the occurrence of
earthquakes soon or later but they do not give information about the location and
time of an earthquake whose preparation stages have already begun. In contrast,
monitoring surface and above surface phenomena during the earthquake prepa-
ration stage may provide clues to the location and time of an impending events.
Beside the anomalous events or processes that may precede an earthquake
(precursory events) and might signal a coming earthquake, the energy built up in
the earth's crust can cause swelling of rocks which result in ground uplift and
tilting in active fault zones. This causes the formation of numerous small cracks
and an unstable condition that may lead to small earthquakes before the main event
(Nelson
2010
). These foreshocks are considered as seismic precursory signals and
usually appear less than 30 days before the main shake (Ihmle and Jordan
1994
;
Reasenberg
1999
, Gavrilov et al.
2008
; Ryabinin et al.
2011
). Thus, significant
ground deformations and the occurrence of successive small shakes in the vicinity
of active faults may be signs for existence of seismic activities leading to a strong
earthquake. However, short-term earthquake prediction through monitoring pre-
cursory events has always been difficult to obtain because earthquake related
processes occur deep beneath the surface. Despite the array of precursors that are
possible to monitor, successful short-term earthquake prediction has so far been
difficult to obtain (Nelson
2010
). In order to produce enough information for
monitoring seismic activities along active fault zones large number of ground
observation stations are necessary. But, satellite-based monitoring methods yield
wider coverage, rich information and higher spatial and spectral resolutions.
Instead of relying on a single precursor for earthquake prediction, different on-site
and remotely-sensed data should be integrated to produce better and more com-
prehensive earthquake studies. There are several national and international space
programs for monitoring earthquake precursory events (Ryabinin et al.
2011
).
3 Earthquake Precursory Signals
3.1 Active Faults
Classical earthquake theories suggest that active faults are the generator of this
event. Small shakes grow into main earthquakes while they are spreading along
