Crustal attenuation characteristics in western Turkey

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Kurtulmuş T. Ö., Akyol N.

GEOPHYSICAL JOURNAL INTERNATIONAL, vol.195, no.2, pp.1384-1394, 2013 (SCI-Expanded, Scopus)

  • Publication Type: Article / Article
  • Volume: 195 Issue: 2
  • Publication Date: 2013
  • Doi Number: 10.1093/gji/ggt318
  • Journal Name: GEOPHYSICAL JOURNAL INTERNATIONAL
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1384-1394
  • Keywords: Elasticity and anelasticity, Seismic anisotropy, Seismic attenuation, Europe
  • Open Archive Collection: AVESIS Open Access Collection
  • Dokuz Eylül University Affiliated: Yes

Abstract

We analysed 1764 records produced by 322 micro- and moderate-size local earthquakes in western Turkey to estimate crustal attenuation characteristics in the frequency range of 1.0 < f < 10 Hz. In the first step, we obtained non-parametric attenuation functions and they show that seismic recordings of transverse and radial S waves exhibit different characteristics at short and long hypocentral distances. Applying a two-step inversion, we parametrized Q( f ) and geometrical spreading exponent b( f ) for the entire distance range between 10 and 200 km and then we estimated separately Q and b values for short (10-70 km) and large (120-200 km) distance ranges. We could not observe significant frequency dependencies of b for short distance range, whereas the significant frequency dependence of b was observed for large distances. Low Q(0) values (similar to 60) with strong frequency dependence of Q (similar to 1.4) for short distances suggest that scattering might be an important factor contributing to the attenuation of body waves in the region, which could be associated to a high degree of fracturing, fluid filled cracks, young volcanism and geothermal activity in the crust. Weak Q frequency dependence and higher Q(0) values for large distances manifest more homogenous medium because of increasing pressure and enhanced healing of cracks with increasing temperature and depth. Q anisotropy was also observed for large hypocentral distance ranges.