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SAFER Test-site: Athens

SAFER Test-site: Athens. Partners: NOA, NKUA, NORSAR. 1995 6.2. 1999 5.9. 1981 6.8, 6.4, 6.3. Corinth rift: fast opening 1cm/y, high seismicity M ~ 7 good azimuthal coverage, close to Athens. NKUA/NORSAR. Development of instrumentation with the aim to apply

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SAFER Test-site: Athens

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  1. SAFER Test-site: Athens Partners: NOA, NKUA, NORSAR

  2. 1995 6.2 1999 5.9 1981 6.8, 6.4, 6.3 Corinth rift: fast opening 1cm/y, high seismicity M ~ 7 good azimuthal coverage, close to Athens

  3. NKUA/NORSAR Development of instrumentation with the aim to apply • Tnow network based location approach. • Tc and Pd on-site calculation approach. • Array based processing approach.

  4. NOA • Development of the algorithm FORMA for the near real-time recognition of changes in the states of seismicity. • Retrospective performance in strong Greek earthquake sequences. • Application in swarm activities in Corinth Gulf. • Criteria for the discrimination between foreshocks and swarms in Corinth Gulf.

  5. Corinth rift is very prone to foreshock and swarm activity Papadopoulos et al. (2000)

  6. Foreshock sequences n=37 , d=81 days Swarms n=64 , d=86 days 11 Feb 1984 18.03.01 12.06.01

  7. Criteria for swarm identification • Minimum number of events=10 (Mogi criterion) • b-value swarm »b-value background • Seismicity rate swarm » seismicity rate background • Probability for the occurrence of n events by chance Ρ <1*10-3

  8. Determination of background seismicity rate • Earthquake catalogue was declustered by a Greek version of the Gardner and Knopoff (1974) algorithm (Latoussakis and Stavrakakis, 1992)

  9. January 2009: onset of swarm activity in Corinth rift

  10. January 2009: onset of swarm activity in Corinth rift

  11. January 2008: termination of swarm activity in Corinth rift

  12. Conclusions 1.Algorithm FORMA performs well enough not only in stronmg earthquake sequences but also in swarm-type activity. 2.Identification of swarm activity is of great importance for reducing false alarms based on wrong foreshock determination.

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