RAPID EARLY WARNING SYSTEM (REWS) for BUCHAREST and INDUSTRIAL FACILITIES

A group of civil engineers and seismologists from the National Institute of Earth Physics (NIEP) in Romania and Karlsruhe University in Germany propose a Rapid Early Warning System (REWS) for the capital city of Bucharest and industrial facilities.

The Romanian capital Bucharest faces a significant earthquake hazard with a 50% chance for an event in excess of 7.6 moment magnitude every 50 years. Within the last 60 years Romania experienced 4 strong Vrancea earthquakes:

Winner of the 2006 IST Prize - National Institute for Earth Physics (RO) for Early Warning System for Strong Earthquakes ( The European IST Prize Awards Ceremony took place on 22 March 2006 at the Hofburg in Vienna. )    In the press:  The Romanian National Institute for Earth Physics is proposed Nominee for the European IST Grand Prize. an article published in Ad Astra ( 07 Oct 2005 )    IST Grand Prize - Invitation letter    IST Grand Prize . a major European competition ( Romanian version )    FP7 International Conference: Opportunities and challenges for Romania ( Romanian version )

• Nov. 10, 1940 (Mw =3D 7.7, 160 km deep);
• March 4, 1977 (Mw =3D 7.5, 100 km deep);
• Aug. 30, 1986 (Mw =3D 7.2, 140 km deep);
• May 30, 1990 (Mw =3D 6.9, 80 km deep).

The 1977 event had catastrophic character with 35 high-rise buildings collapsed and 1500 causalities, the majority of them in Bucharest. A Rapid Early Warning System (REWS) based on the traveltime differences between the primary P-wave and the destructive S-wave allows a warning time of about 25 s (Fig 1). Peculiarities of the Romanian intermediate depth seismicity such as the stationary epicenters and the stability of radiation patterns, and a line-of-sight connection between the epicentral area and the capital allow to design a simple and robust REWS.

Simplicity and robustness of the system are sought in order to reduce the risk of false alarms, which is crucial for making the system cost-beneficial.

The earthquakes threatening the capital are intermediate-depth events. Moreover, source mechanisms are extremely stable for larger and smaller events so that a projection of the level of ground motion to be expected in Bucharest can be based on the amplitude of the epicentral P wave rather than on the cumbersome determination of magnitude and depth. This feature allows the design of a simple, robust, and fast REWS.

The real-time detection of the dangerous seismic waves from Vrancea area is used for strong earthquakes as a Rapid Early Warning System (REWS). REWS uses the time interval (that is about 25-28) seconds between the moment when earthquake is detected at the surface in the epicentre area (Vrancea) and the moment of arrival in the protected sites. This time interval depends on the depths and propagation conditions of the earthquake.

REWS installed in Vrancea area has four important modules:
-    local seismic network for detection ,
-    2 acquisition centres and computing facilities,
-    redundant communication network,
-    distribution to users

The detection of the P waves in epicenter is the first step in the early warning process. Three 3 axis strong motion accelerometers perform the detection in two different locations situated at about 8 km far (next figure ). The first site is situated in Vrancioaia (VRI). In the second location, Plostina (PLOR) site (Vrancea area), are installed two accelerometers, one in a 50 m borehole and another one on the surface on a vault.

Using the first second of the recording is possible to have a preliminary estimation of the magnitude of the earthquake. A scale of eight levels is associated to acceleration values detected from P waves. A seismic early warning alarm is triggered having the following details: time, peak acceleration value and level of triggering. An interactive analysing module can modify the parameters of the alarm if in the next seconds the acceleration of the seismic waves is increased.

REWS works in the following steps: detection of the P waves, first arrivals analysis (fast Fourier analysis and acceleration detection coincidence on more than one accelerometer), alarm generation, sending of the alarm at the users (including also SMS and email).

The communication is one of the most important parts of the REWS. Redundant radio links ensure the communication between Vrancioaia and Plostina sites and between Vrancioaia and Romanian Data Center in Bucharest.

The distribution at the users is the last step in the early warning process. At the moment this is insured using dedicated internet connections. A dedicated device designed by NIEP staff connected to the REWS. PC computer (by using TCP/IP communication) is the interface between central station in Bucharest and user.s critical process. This device can be configured to trigger at different levels following the user.s requirements.

At this moment the REWS is in testing phase with one user (a sterilisation facility which uses a nuclear source) which agreed to the testing conditions.

Related Links:

The European IST Prize - www.ist-prize.org
Ad Astra - an online project devoted to the Romanian scientific community - www.ad-astra.ro
ROINTERA project - www.rointera.ro