The crustal anisotropy pattern in the epicentral area of the 2008 Mw 6.4 earthquake in northwest Peloponnese, Greece
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Κωνσταντινόπουλος, Δημήτριος
Γιαννόπουλος, Δημήτριος
Σώκος, Ευθύμιος
Κωνσταντίνου, Κωνσταντίνος
Τσελέντης, Γεράσιμος
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Abstract
On June 8, 2008, a Mw 6.4 earthquake occurred on a strike-slip fault in north-west Peloponnese, Greece, 35 km southwest of the city of Patras. We analysed part of the aftershock sequence of the 2008 earthquake, recorded by a portable network of six stations and a permanent station of the Hellenic Unified Seismological Network, in order to perform a shear wave splitting analysis. We determined fast polarization directions φ, and normalized time-delays dt between the fast and slow components. The average value of dt was calculated at 1.7 ±0.5 ms/km, while φ values varied between 155 deg ±8 deg and 11deg ±9 deg , with an average of 170 deg ±9 deg . The observed φ values at all stations were inconsistent with the regional stress field, which is characterized-by a general E-W orientation of the maximum horizontal compressive stress. On the contrary, the observed fast directions appear to intersect the strike of the causative fault (210o) in smaller angles than the regional principal compressive stress axis. The findings of this work are consistent with those of previous studies in the area, reflecting possibly the presence of a locally rotated principal stress axis to more favorable angles to the strike of the fault of the 2008 strong earthquake.
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Keywords
Shear wave splitting, Stress field, Wave propagation, Seismic anisotropy