Tríkala, Greece
Tríkala, Greece

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Papathanassiou G.,Aristotle University of Thessaloniki | Valkaniotis S.,Koronidos Str. | Ganas A.,Institute of Geodynamics | Grendas N.,Aristotle University of Thessaloniki | Kollia E.,Institute of Geodynamics
Engineering Geology | Year: 2017

On November 17, 2015 a strong, shallow earthquake (Mw = 6.5) occurred on the island of Lefkada along a N20 ± 5°E, east-dipping strike-slip fault with right-lateral sense of slip. The event triggered environmental effects that were mainly mapped at the western part of the island while moving towards the eastern part, the severity of the earthquake-induced failures decreased. The most characteristic geological effects that were triggered by the earthquake were slope failures including rock falls, rock slides and landslides. The spatial density of the failures follows an exponential increase with slope-angle and decreases for values larger than 55°. Small-size liquefaction phenomena such as sand craters and ejection of fine-grained sand through ground cracks were documented at the coastal area of Vassiliki. The epicentral intensity was assessed based on the definitions of Environment Seismic Intensity scale as VIII ESI-07, and the macroseismic epicenter (VIII up to IX) was located at the coastal area of Egremnoi (west of Athani village, south Lefkada). In addition, comparing the severity of earthquake-induced failures on the main road network, triggered by the 2003 and 2015 events, it is concluded that the behavior of the protection measures such as fences and walls, could be generally characterized as satisfactory. On the contrary, the similarity of the structural failures triggered by the 2003 event with the ones triggered by the 2015 earthquake, documented at the port of Vassiliki, indicates that the post-2003 constructed port facilities failed to guarantee the functionality of the port of Vassiliki. © 2017 Elsevier B.V.


Ganas A.,Institute of Geodynamics | Elias P.,Astronomy & Astrophysics | Bozionelos G.,National and Kapodistrian University of Athens | Papathanassiou G.,Aristotle University of Thessaloniki | And 5 more authors.
Tectonophysics | Year: 2016

On November 17, 2015 07:10:07 UTC a strong, shallow Mw6.5 earthquake, occurred on the island of Lefkada along a strike-slip fault with right-lateral sense of slip. The event triggered widespread environmental effects at the south and western part of the island while, the intensity and severity of these earthquake-induced deformations is substantially decreased towards the eastern part of the island. Relocation of seismicity and inversion of geophysical (GPS, InSAR) data indicate that the seismic fault runs parallel to the west coast of Lefkada, along the Aegean – Apulia plate boundary. The fault plane strikes N20 ± 5°E and dips to east with an angle of about 70 ± 5°. Coseismic deformation was measured in the order of tens of centimeters of horizontal motion by continuous GPS stations of NOANET (the NOA GPS network) and by InSAR (Sentinel 1 A image pairs). A coseismic uniform-slip model was produced from inversion of InSAR data and permanent GPS stations. The earthquake measured Mw = 6.5 using both the geodetic moment produced by the slip model, as well as the PGD relation of Melgar et al. (2015, GRL). In the field we observed no significant vertical motion of the shoreline or surface expression of faulting, this is consistent with the predictions of the model. The interferograms show a large decorrelation area that extends almost along all the western coast of Lefkada. This area correlates well with the mapped landslides. The 2003–2015 pattern of seismicity in the Ionian Sea region indicates the existence of a 15-km seismic gap offshore NW Cephalonia. © 2016 Elsevier B.V.

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