NHESS Natural Hazards and Earth System Sciences NHESS Nat. Hazards Earth Syst. Sci. 1684-9981 Copernicus Publications Göttingen, Germany 10.5194/nhess-13-45-2013 Stress distribution and seismicity patterns of the 2011 seismic swarm in the Messinia basin, (South-Western Peloponnesus), Greece Chouliaras G. 1 Drakatos G. 1 Pavlou K. https://orcid.org/0000-0002-6935-5809 2 Makropoulos K. 1 Institute of Geodynamics, National Observatory of Athens, Lofos Nymfon, 11810 Athens, Greece Department of Geophysics – Geothermics, University of Athens, 15784 Athens, Greece 10 01 2013 13 1 45 51 Copyright: © 2013 G. Chouliaras et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://nhess.copernicus.org/articles/13/45/2013/nhess-13-45-2013.html The full text article is available as a PDF file from https://nhess.copernicus.org/articles/13/45/2013/nhess-13-45-2013.pdf

In this investigation we examine the local stress field and the seismicity patterns associated with the 2011–2012 seismicity swarm in the Messinia basin, south-western Peloponnesus, Greece, using the seismological data of the National Observatory of Athens (NOA). During this swarm more than 2000 events were recorded in a 12 month period by the Hellenic Unified Seismological Network (HUSN) and also by the additional local installation of four portable broadband seismographic stations by NOA. <br><br> The results indicate a Gaussian distribution of swarm activity and the development of a seismicity cluster in a pre-existing seismic gap within the Messinia basin. Centroid Moment Tensor solutions demonstrate a normal fault trending northwest–southeast and dipping to the southwest primarily due to an extensional stress field. During this seismicity swarm an epicentre migration of the three largest shocks is observed, from one end of the rupture zone in the north-western part of the cluster, towards the other edge of the rupture in the south-eastern part of the cluster. This migration is found to follow the Coulomb failure criterion that predicts the advancement and retardation of the stress field and the patterns of increases and decreases of the seismicity rate (b-value) of the frequency–magnitude relation.

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