An assessment of the microseismic activity and focal mechanisms of the Izmir (Smyrna) area from a new local network (IzmirNET)

Izmir metropolitan area is one of the biggest cities of Turkey in terms of population and industrial density. Amount of recordings and quality of located events increased since the new local seismic array, IzmirNET, was installed in 2008. Present study addresses to elucidate seismotectonics of Izmir vicinity by a new data set and reveal first results of seismological analysis obtained for 4.5 years.930 small earthquakes are well located within less than 1.0 km horizontal error (RMS ≤ 0.15 s) over a total of 1421 recorded events. Data were processed by using SEISAN Earthquake Analysis Software implemented at SeismoLab of Dokuz Eylul University. The Orhanli-Tuzla Fault Zone and Izmir faults are capable of producing a destructive earthquake. Events show clear clusters around the Outer Bay of Izmir Gulf and Sigacik Bay. We also detected some dense clusters Sigacik Bay to the South, and in the outer bay of Izmir Gulf along NW-SE direction.We investigated kinematics of active faults around the Izmir and Foca areas by using 41 focal mechanism solutions from different algorithms. Foca is located 60 km in the NW direction of Izmir. Mechanisms generally resulted in pure normal or dominant normal faulting with minor strike-slip components in agreement with the kinematics of the other fault zones in Western Turkey. A stress tensor study using selected fault plane solution indicates that the study area is under extension regime in an N-S direction with 71° plunge for maximum compressive principal stress axis (S1), and closer to horizontals for intermediate (S2) and minimum compressive principal stress axis (S3).