Deep Seismic Structure of the SW Segment of the Hellenic Subduction Zone : the ULYSSE Cruise Preliminary Results
Abstract
The Hellenic Subduction zone is characterized by a moderate convergence rate of ~ 4 cm/yr and by the highest rate of current seismicity in Europe. Several large magnitude (M 7.5 - 8) earthquakes occurred offshore the Peloponnesus peninsula at the turn of the 19th to 20th century. The 400-km-long south-western segment has been the site of the largest historical earthquake of Europe, the AD 365 M8+ earthquake, which occurred offshore South of Peloponnesus and near SW Crete Island, and which generated a devastating tsunami that spread into the Nile Delta region and along the Adriatic Sea. The megathrust fault and the outer forearc domain of this SW segment have been the target in November 2012 of the ULYSSE deep penetration seismic experiment on board the N/O Le Pourquoi Pas? of IFREMER and we present here the preliminary results. We have carried out two 250-km-long refraction OBS transects across the Kythirian Straits coincident with deep multichannel reflection seismic (MCS) profiles by using a 11 000 cu.inch airgun source of IFREMER and 25 OBH/OBS from GEOMAR. An additional set of ~650 km of MCS profiles has been collected over the outer forearc domain despite bad weather conditions. Chirp and multi-beam bathymetric data have also been collected along some of those profiles. These data are now being processed with the objectives of imaging the megathrust fault in the depth range of 15-40 km and identifying the structural markers of the updip and downdip limits of the potential seismogenic zone (i.e. the forearc backstop nature and the upper plate Moho up to its intersection with the downgoing plate), as well as their along-strike variations. These results will furthermore be discussed and analysed together two other datasets that have been collected in the frame of the past EU THALES WAS RIGHT project : a 1-year dataset of local seismicity recorded by a land-OBS network and an onshore 3-D Receiver Functions dataset which provides constraints on the slab towards greater depths.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.T43D2693L
- Keywords:
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- 3060 MARINE GEOLOGY AND GEOPHYSICS Subduction zone processes;
- 7240 SEISMOLOGY Subduction zones;
- 8170 TECTONOPHYSICS Subduction zone processes;
- 3025 MARINE GEOLOGY AND GEOPHYSICS Marine seismics