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In the last few decades economic losses due to natural disasters have increased
exponentially worldwide and little progress has been seen in reducing
their rate of fatalities. This also holds for earthquake disasters and
is mainly due to increasing population and industrial density in high hazard
and vulnerability areas. Although the prediction of earthquakes is not yet
practicable, current technology allows prompt identification of the onset of
any dangerous seismic event. Hence early warning and rapid disaster information
systems are becoming important means for strengthening prevention
and social resilience against the adverse effects of major natural
events and should therefore become the keystones of disaster mitigation.
The term early warning is now widely used with various meanings in scientific,
economic and sociological communities. Even in the scientific
world the term is used in slightly different ways although there is a growing
consensus in defining early warning as all the action that can be taken
during the lead time of a catastrophic event. The lead time is defined as the
time elapsing between the moment when the occurrence of a catastrophic
event in a given place is reasonably certain and the moment it actually occurs.
Typical lead times are of the orders of seconds to tens of seconds for
earthquakes, minutes to hours for tsunamis, and hours to days for landslides,
floods and volcanic eruptions.
In more general terms, early warning is the provision of timely and effective
information, through identified institutions, allowing individuals
exposed to a hazard to take action in order to avoid or reduce their risk and
prepare for effective response. |
