SEISMICITY OF THE 24 MAY 2014 MW 7.0 AEGEAN SEA EARTHQUAKE SEQUENCE ALONG THE NORTH AEGEAN TROUGH

The northern Aegean Sea was hit by a large size (M_w=7.0) earthquake on 2014 May 24. Centroid moment tensor solutions for 40 events with moment magnitudes (M_w) between 3.3 and 7.0 are computed by applying a waveform inversion method on data from the Turkish and Greek broadband seismic networks. The time span of data covers the period between 2014 May 24 and 2014 June 26. The mainshock is a shallow focus strike-slip event at a depth of 15 km. Focal depths of aftershocks range from 6 to 30 km. The seismic moment (M_o) of the mainshock is estimated as 4.60 × 10¹⁹ Nm. The calculated rupture duration of the North Aegean Sea mainshock is 40 s. The focal mechanisms of the aftershocks are mainly strike-slip faulting with a minor normal component. The geometry of focal mechanisms reveals a strike-slip faulting regime with NE-SW trending direction of T-axis in the entire activated region. A stress tensor inversion of focal mechanism data is performed to acquire a more accurate picture of the northern Aegean Sea stress field along the North Aegean Trough. The stress tensor inversion results indicate a predominant strike-slip stress regime with a NW-SE oriented maximum principal compressive stress. With respect the newly determined focal mechanisms, the effect of the propagating of the North Anatolian Fault into Aegean Sea is very clearly pronounced. According to high-resolution hypocenter relocation of the North Aegean Sea seismic sequence, three main clusters are revealed. The aftershock activity in the observation period between 2014 May 24 and 2014 July 31 extends from the mainshock cluster from NE to the SW direction. Seismic cross-sections indicate that a complex pattern of the hypocenter distribution with the activation of seventeen segments. The best constrained focal depths indicate that the aftershock sequence is mainly confined in the crust (depth ≤ 30 km) and is operating in the approximate depth range from 1.5 to 30 km. Consequently, Coulomb stress analysis is performed to calculate the stress transfer and correlate it with the activated region. Positive lobes with stress more than 3 bars are obtained, indicating that these values are large enough to increase the Coulomb stress failure towards ENE-WSW direction.