On UrEDAS and HERAS - Real-time Earthquake Disaster Prevension Systems -


Yutaka NAKAMURA
UrEDAS, Urgent Earthquake Detectin and alarm system, is an integrated real-time earthquake warning system. Unlike conventional earthquake warning systems which generally issue an alarm when earthquake motion at the site exceeds a pre-set level, UrEDAS judges the destructive potential of an earthquake on the basis of the relation between magnitude and epicentral distance of the earthquake, and issues a necessary warning for a certain area which may sustain damage. UrEDAS consists of a single station with a three-component seismometer. UrEDAS performs two-step warning: within four seconds after the P-wave arrival, it estimates the earthquake parameters and issues a preliminary alarm. At the arrival of S wave, it improves the estimates and updates the warning. When several UrEDAS units are used, the data from each unit are synthesized to produce more definitive information.

HERAS, Hazards Estimation and Restoration Aid System, estimates the degree of the damage caused by the earthquake based on the synthesized information from UrEDAS units and on the relation between earthquake strong motion and damage, and display the result invisually within five minutes after P-wave arrival.