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| Titel |
The 2015, Mw 6.5, Leucas (Ionian Sea, Greece) earthquake: Seismological and Geodetic Modelling |
| VerfasserIn |
Vasso Saltogianni, Tuncay Taymaz, Seda Yolsal-Çevikbilen, Tuna Eken, Fanis Moschas, Stathis Stiros |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127175
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| Publikation (Nr.) |
 EGU/EGU2016-7018.pdf |
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| Zusammenfassung |
| A cluster of earthquakes (6<Ms <7) characterized by strike slip faulting have occurred along
the NW edge of the Aegean Arc in the Ionian Sea, the most seismically active region in
Greece, in the last 30 years. The most recent earthquake was the 2015 (Mw 6.5) Leucas
(Lefkada) earthquake. The modelling of these earthquakes, some of which are double events
(2003 Leucas; 2014 Cephalonia) is a challenge for two main reasons. First, the geography of
the area limits the distribution of the available seismological and GNSS stations and the
correlations of INSAR data. Second, the structural pattern of the area indicates distributed
thrusting but recent earthquakes are confined to the west margin of the Aegean Arc, usually
assigned to the Cephalonia Transform Fault (CTF), and are dominated by strike slip
faulting.
In order to contribute to the understanding active tectonics along this critical region, our
study was based on the independent analysis of the seismological and geodetic signature of
the 2015 earthquake and the on the joint evaluation of the inferred models on the basis of the
fault pattern of the area and of previous earthquakes.
First, based on teleseismic long-period P- and SH- and broad-band P-waveforms a
point-source solution at the SW part of Leucas yielded dominantly right-lateral strike-slip
faulting mechanisms (strike: 23o, dip: 68o, rake: -170o) with a shallow focal depth (h: 9 km)
and with seismic moment of Mo: 10.4x1018 Nm. Furthermore, the rupture history of the
earthquake was obtained by applying a new back-projection method that uses teleseismic
P-waveforms to integrate the direct P-phase with reflected phases from structural
discontinuities near the source. In the slip inversion the faulting occurs on a single fault plane
(strike and dip are obtained from the best fitting point-source solution) and slip (rake) angle
varied during the whole rupture process.
Second, co-seismic displacements were derived from eight permanent and one campaign
GPS stations spread in the near and far field of the meizoseismal area. Significant horizontal
slip was recognized, with a maximum dislocation of 36 cm in the SW part of Leucas island.
Inversion of GPS-derived displacements using the new TOPological INVersion (TOPINV)
algorithm permitted to model a nearly vertical strike slip fault (strike: 15o, dip: 78o, rake:
-175o and Mo: 11.4x1018 Nm), fully controlled by a variance co-variance matrix, and
subsequently a variable-slip model. An alternative low-angle strike slip fault was also
computed. Both models were obtained assuming all nine variables defining a fault variable
fully constrained, simply each one taking possible values independent of each other in a
broad space.
The matching of the independently computed seismological and geodetic fault-models
indicate that the 2015 earthquake was associated with a nearly strike-slip fault just offshore
SW Leucas, and along with the events in the last 30 years, it indicates gradual, piece-wise
rupture of the west edge of a shear zone which is superimposed on the regional compressional
margin of the Aegean Arc. |
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