An active extensional deformation example: 19 May 2011 Simav earthquake (Mw=5.8), Western Anatolia, Turkey


DEMİRCİ A., ÖZDEN S. , BEKLER T. , Kalafat D. , PINAR A.

JOURNAL OF GEOPHYSICS AND ENGINEERING, cilt.12, ss.552-565, 2015 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 12 Konu: 4
  • Basım Tarihi: 2015
  • Doi Numarası: 10.1088/1742-2132/12/4/552
  • Dergi Adı: JOURNAL OF GEOPHYSICS AND ENGINEERING
  • Sayfa Sayıları: ss.552-565

Özet

The Simav Earthquake that occurred on 19 May 2011 in western Turkey was investigated on the basis of seismological data and geological observations. Approximately WNW-ESE trending surface ruptures were observed on the Simav Fault. The focal mechanism parameters of the earthquake (Mw = 5.8) and its aftershocks (Mw > 3.5) were estimated using time-domain moment tensor inversion. A total of 2245 events were located with Geiger's conventional absolute location method then relocated using the double difference (DD) algorithm. The calculated locations at a depths between 2 and 16 km were found to be consistent with Coulomb stress variation in the area. Average variance reduction (VR) of the solutions was calculated as similar to 70%. The focal parameters of strike dip and slip of the main shock, occurring at a depth of 11 km dipping towards the NNE, were estimated at 277, 62 and -92, respectively. The most striking indication of the study is that the area is dominated by normal faults with mainly WNW-ESE trends. It is also concluded that earthquakes in the region are caused by an active and regional NNE-SSW (N 12 degrees E) trending (sigma(3) axis) extension regime. The mean stress ratio is 0.80, indicating a triaxial stress state. This extension is probably associated with a slab-pull force and /or roll-back due to the complex subduction process of the African Plate beneath Anatolian block along both the Hellenic and Cyprus arcs in the eastern Mediterranean region.