Whatever the hazard, early warnings would work well when adequate technological capability combines with proper decision-making and dissemination systems, and prepared communities.
In the case of tsunamis, an effective warning and mitigation system means people living in vulnerable coastal areas know how to respond when a potentially destructive tsunami may be approaching.
Tsunami warning systems are made up of three components.
First, an international or regional arrangement (like PTWC) that detects earthquakes in real time, evaluates their tsunami-creating potential, looks for sea level changes and issues specific messages.
Second, country disaster management organisations that receive such warning messages and make national or local level decisions (alert? stand-by? evacuate?). They activate communication systems and response plans already agreed upon.
Third, residents in areas at risk are educated and trained.