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| Titel |
Improving seismic crustal models in the Corinth Gulf, Greece and estimating source depth using PL-waves |
| VerfasserIn |
Jiri Vackar, Jirí Zahradník |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250076964
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| Zusammenfassung |
| A recent shallow earthquake in the Corinth Gulf, Greece (Mw 5.3, January 18, 2010; Sokos
et al., Tectonophysics 2012) generated unusual long-period waves (periods > 5
seconds), well recorded at several near-regional stations between the P - and S-wave
arrival. The 5-second period, being significantly longer than the source duration,
indicates a structural effect. The wave is similar to PL-wave or Pnl-wave, but
with shorter periods and observed in much closer distances (ranging from 30 to
200Â km).
For theoretical description of the observed wave, structural model is required. No existing
regional crustal model generates that wave, so we need to find another model, better in terms
of the  PL-wave existence and strength. We find such models by full waveform inversion
using the subset of stations with strong PL-wave. The Discrete Wavenumber method
(Bouchon, 1981; Coutant 1989) is used for forward problem and the Neighborhood
Algorithm (Sambridge, 1999) for stochastic search (more details in poster by V. Plicka and J.
Zahradník).
We obtain a suite of models well fitting synthetic seismograms and use some of these
models to evaluate dependence of the studied waves on receiver distance and azimuth as well
as  dependence on source depth. We compare real and synthetic dispersion curves (derived
from synthetic seismograms) as an independent validation of found model and discuss
limitations of using dispersion curves for these cases. We also relocated the event in the new
model.
Then we calculate the wavefield by two other methods: modal summation and ray theory
to better understand the nature of the PL-wave.
Finally, we discuss agreement of found models with published crustal models in the
region. The full waveform inversion for structural parameters seems to be powerful tool for
improving seismic source modeling in cases we do not have accurate structure model of
studied area. We also show that the PL-wave strength has a potential to precise the earthquake
depth.
Acknowledgement:
Seismograms of the Hellenic Unified Seismic Network were used, including the stations
co-operated by the Charles University in Prague. The research was financially supported from
the following grants in the Czech Republic: GACR 210/11/0854 and MSM 0021620860. |
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