Journal of Seismology

, 13:1 | Cite as

Problematic non-double-couple mechanism of the 2002 Amfilochia Mw5 earthquake, Western Greece

Original article

Abstract

Two seismic agencies reported a very low double-couple percentage (DC%) of the Amfilochia earthquake, of about 30% and 60%, by Schweizerischer Erdbebendienst and Mediterranean Very Broadband Seismographic Network, respectively. Near-regional waveforms, carefully analyzed in this paper for the DC%, suggested a higher DC%, ranging from 75 to 100, dependent on the uncertainty of the source position (optimum value DC% = 93). Using a statistical F test, forward modeling of the near-regional data with a single-event low-DC% source yields a significantly worse waveform match. The fit of near-regional data can be further improved (although at the 90% significance level only) when considering a speculative two-event model. The same model, when viewed at the very-low frequency range, reaches the very low DC% values. However, two features make the two-event model unlikely: The two subevents strongly differ in their focal mechanism, and their mutual separation (3.5 s) is larger than the expected duration of this earthquake. Therefore, the two-source model appears to be nothing but an interesting equivalent representation of the non-DC model, providing some insight into the possible origin of the apparently low DC%. Preference is given to the simple interpretation, most clearly supported by the near-regional data, that the Amfilochia earthquake was an almost pure-shear event.

Keywords

Moment tensor Iterative deconvolution Regional data Waveform inversion Deviatoric solution Source complexity Focal mechanism 

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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Petra Adamova
    • 1
  • Efthimios Sokos
    • 2
    • 3
  • Jiri Zahradnik
    • 4
  1. 1.Academy of Sciences, Institute of GeophysicsPragueCzech Republic
  2. 2.Seismological LaboratoryUniversity of PatrasPatrasGreece
  3. 3.Institute of GeodynamicsNational Observatory of AthensAthensGreece
  4. 4.Faculty of Mathematics and PhysicsCharles UniversityPragueCzech Republic

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