A study of the 8 January 2013 Mw5.8 earthquake sequence (Lemnos Island, East Aegean Sea)

Abstract

Abstract The 8 January 2013 Mw5.8 earthquake sequence south of Lemnos Island (East Aegean Sea) is investigated. The focal mechanisms of the strongest events, obtained by waveform modelling, together with the HypoDD relocated epicentres, clearly show the activation of a dextral strike-slip fault, no more than 14 km in length, trending N60°E, and extending in depth from approximately 3 to 25 km, with the best determined focal depths in the range 3 to ~ 13 km. The distribution of slip onto the fault plane shows a single patch of 7 × 8 km 2 , where the average and the peak slip are equal to 30 cm and 130 cm, respectively. The locus of the peak slip is well resolved to be ~ 2.5 km away from the hypocentre, towards SW. The slip model was used to forward model the distribution of Peak Ground Velocity (PGV in cm/s) in the near source. The PGV contours imply that if any directivity is associated with this event, this is towards SW. The sequence in study, is located in the eastward extension of the Agios Efstratios Fault Zone, which was the locus of the February 19, 1968 Mw7.2 earthquake, which produced surface rupture on the island itself. The Agios Efstratios Fault Zone terminates off shore, south of Lemnos Island. The 2013 sequence is not connected, in a strict sense, with the Agios Efstratios Fault. It indicates rupture of another fault, approximately parallel to it, and the characteristics of the sequence are in accordance with the regional tectonics and previous knowledge. The Coulomb stress change associated with the mainshock, is also examined to evaluate any significant enhance of stresses along the Agios Efstratios Fault Zone.