Earthquake Early Warning Systems

[Gregory]

Earthquake Early Warning Systems

Author: Paolo Gasparini Gaetano Manfredi Jochen Zschau | Size: 8.68 MB | Format: PDF | Quality: Unspecified | Publisher: springer | Year: 2007 | pages: 371 | ISBN: 9783540722403

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. Although the definition of lead time for non-seismic hazards may be
ambiguous (the term “reasonably certain” may need a more precise probabilistic definition), for earthquakes the definition is unequivocal as the lead time will start when the first waves are released by the earthquake source. Indeed, the physical basis for earthquake early warning is simple: strong ground shaking is caused by shear-waves and by the subsequent surface waves which travel at about half the speed of the primary waves and much slower than electromagnetic signals transmitted wireless and/or by cable.

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