THE ROMANIAN INSTITUTE FOR APPLIED SEISMOLOGY
An Early Warning Sistem for Bucharest
Abstract
An Early Warning System (EWS) for the Romanian capital Bucharest is proposed.
The design exploits the stationarity in space of the hypocenters (very clustered), the stationary of the radiation pattern of large epicentral distance to Bucharest ( 150 km),
the lign-of-sight connection between the mountainous epicentral area and the lowland where Bucharest has been built. These properties allow the operation of a simple ,
fast, robust and cheap EWS. The warning time is about of 25 s with a possible confirmation/rejection stage 10-15 s later.
Introduction
The discussin of Early Warning System (EWS) for natural dizasters has intensified towards the end of the IDNDR. The value of EWS for hazards with long warning time
such as tsunamis, volcanic activities, tornadoes is undisputed. There is an obvious lack of regional warning capacity for tsunamis and by far not all volcanoes threatening urban centers are properly monitored. In case of earthquakes, warning times are fairly small, ranging from seconds to a maximum of about one minute for Mexico City.
However, even a small time window can provide opportunities to automatically trigger measures such as shutdown computers ; reroute electrical power ; shutdown disk drives; shutdown high precision facilities; shutdown airport operations; shutdown manufacturing facilities; stop trains; shutdown high energy facilities; shutdown gas distribution; alert hospital operating rooms; open fire station doors; start emergency generators; stop elevators in a safe pozition; shutoff oil pipelines; issue audio alarms; shutdown rafineries; shutdown nuclear power plants; shutoff water pipelines; maintain safe-state in nuclear facilities (Harben, 1991). Only few of these options remain once the warning time is down to a few seconds.
In this site we disuss the seismological boundary conditions of an EWS (SAS) for the Romanian capital of Bucharest. The earthquakes threatening the capital are intermediate deep events with magnitudes close to Mw = 8.0 at an almost fixed epicentral distance of about 150 km. The traveltime difference between the distructive S-wave arriveing in Bucharest and the epicentral P-wave is always greater than 25 s, which represents the maximum possible warning time. Moreover mechanism are extremely stable for larger and smaller events so that a projection of level of ground motion to be expected in Bucharest can be based on the amplitude of the epicentral P-wave rather than on cumbersome determination of magnitude and depth. This feature allows the design of a simple, robust and fast EWS.
