3-D crustal structure along the North Anatolian Fault Zone in north-central Anatolia revealed by local earthquake tomography

Seda Yolsal-Çevikbilen, C. Berk Biryol, Susan Beck, George Zandt, Tuncay Taymaz, Hande E. Adiyaman, A. Arda Özacar

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Abstract

3-D P-wave velocity structure and V p/V s variations in the crust along the North Anatolian Fault Zone (NAFZ) in north-central Anatolia were investigated by the inversion of local P- and S-wave traveltimes, to gain a better understanding of the seismological characteristics of the region. The 3-D local earthquake tomography inversions included 5444 P- and 3200 S-wave readings obtained from 168 well-located earthquakes between 2006 January and 2008 May. Dense ray coverage yields good resolution, particularly in the central part of the study area. The 3-D V p and V p/V s tomographic images reveal clear correlations with both the surface geology and significant tectonic units in the region. We observed the lower limit of the seismogenic zone for north-central Anatolia at 15 km depth. Final earthquake locations display a distributed pattern throughout the study area, with most of the earthquakes occurring on the major splays of the NAFZ, rather than its master strand. We identify three major high-velocity blocks in the mid-crust separated by the I.zmir-Ankara-Erzincan Suture and interpret these blocks to be continental basement fragments that were accreted onto the margin following the closure of Neo-Tethyan Ocean. These basement blocks may have in part influenced the rupture propagations of the historical 1939, 1942 and 1943 earthquakes. In addition, large variations in the V p/V s ratio in the mid-crust were observed and have been correlated with the varying fluid contents of the existing lithologies and related tectonic structures.

Original languageEnglish (US)
Pages (from-to)819-849
Number of pages31
JournalGeophysical Journal International
Volume188
Issue number3
DOIs
StatePublished - Mar 1 2012

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Keywords

  • Body waves
  • Continental tectonics: strike-slip and transform
  • Crustal structure
  • Seismic tomography
  • Seismicity and tectonics

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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