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.