Real-time Seismic Monitoring in the Greek Region: An Example from the 17 October 2005 East Aegean Sea Earthquake Sequence

Modern seismic networks can record high-quality digital data and transmit them back to a data-collection center in near real-time. This allows seismologists to monitor any ongoing seismic activity efficiently by determining the parameters of each earthquake, such as epicentral location and local magnitude. In addition, more recent developments during the last decade have made possible the inversion of regional waveforms for moment tensor derivation (e.g.. Ekström et al., 1998; Kao and Jian, 1999; Pondrelli et al., 2002). All such waveform processing can be performed fully automatically, giving scientists the opportunity to have a detailed picture of the seismicity in near real-time. Greek region exhibits the highest seismicity in Europe and has experienced destructive earthquakes several times in the past (Papazachos and Papazachou, 1997). Therefore, it is particularly important to be able to monitor any seismic activity quickly and efficiently. The newly installed Hellenic broadband seismic network (HL) offers such capabilities by providing digital three-component waveform data recorded at 22 stations that cover the Greek region. This paper describes the network operation and routine waveform data processing, using as an example case the recent seismic unrest in the eastern Aegean Sea close to the Turkish coast. The analysis presented here also gives the first results on the spatial/temporal distribution of this seismic sequence and the faulting mechanism of 15 events with moment magnitudes between 3.9–5.6.