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Journal of Seismology

, Volume 13, Issue 4, pp 633–646 | Cite as

A high-resolution aftershock seismicity image of the 2002 Sultandaği-Çay earthquake (Mw = 6.2), Turkey

  • Mehmet Ergin
  • Mustafa Aktar
  • Serdar Özalaybey
  • Mustafa C. Tapirdamaz
  • Oguz Selvi
  • Adil Tarancioglu
Original article

Abstract

A moderate-size earthquake (Mw = 6.2) occurred on 3 February 2002 (07:11:28 GMT) in the Sultandağı-Çay region of southwest Turkey. The mainshock was followed by a strong aftershock of Mw = 6.0 just 2 h after the mainshock, at 09:26:49 GMT. A temporary seismic network of 27 vertical component seismometers was installed to monitor aftershock activity. One thousand sixty nine aftershocks (0.2 < ML < 3.3) were recorded during the period from 5 to 10 February 2002. We analyzed the P and S arrival times and P wave first motion data to obtain high-quality hypocenters and focal mechanisms, which revealed fine details of the fault zone. We infer that the mainshock has ruptured a segment of the Sultandağ Fault Zone that is approximately 37 km long and 7 km wide at depth. The average slip over the rupture plane during the mainshock is estimated to be 32 cm. The linear distribution of the aftershocks and the location of the mainshock epicenter suggest that rupture has initiated in the eastern bending of the fault and propagated unilaterally to the west. The majority of fault plane solutions indicate E–W to ESE–WNW striking oblique–normal faulting mechanisms with an average dip angle of 62° N ± 10° . The high-resolution aftershock seismicity image also shows that faulting involved a complex array of synthetic and possibly antithetic structures during the evolution of the aftershock sequence. The steady increase of the b value towards the west implies that the highest moment release of the mainshock occurred to the west of the epicenter. The study clearly shows the activation of the WNW–ESE-trending Sultandağ Fault Zone along the southern margin of the Akşehir-Afyon Graben (AAG). The westernmost end of the aftershock activity corresponds to a structurally complex zone distinct from the main rupture. It is characterized by both ENE–WSW- and NNE–SSW-trending oblique-slip normal faulting mechanisms, the latter being associated with the NNE–SSW-trending Karamık Graben. The intersection of these two grabens, AAG and Karamık Graben, provides abundant faults available for failure in this region. The occurrence pattern of large events in recent years indicates a possible migration of earthquakes from east to west. Thus, we conclude that this has an important implication for earthquake hazard for the city of Afyon, which lies along the same fault line and only 20 km west of the termination point of the aftershock zone.

Keywords

Aftershock Focal mechanism b values Stress tensor Aegean extension 

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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Mehmet Ergin
    • 1
  • Mustafa Aktar
    • 2
  • Serdar Özalaybey
    • 1
  • Mustafa C. Tapirdamaz
    • 1
  • Oguz Selvi
    • 1
    • 3
  • Adil Tarancioglu
    • 1
  1. 1.TUBITAK—Marmara Research CenterGebzeTurkey
  2. 2.Department of GeophysicsBogazici University, Kandilli Observatory and Earthquake Research InstituteIstanbulTurkey
  3. 3.Yildiz Technical University, Natural Sciences Research CenterIstanbulTurkey

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