Relationships among source parameters of aftershocks of the October 1, 1995 Dinar (Turkey) earthquake



E. Yalçınkaya* and Ö. Alptekin*


*Istanbul University, Department of Geophysical Engineering, 34850 Avcılar, Istanbul, Turkey.



(Received 29 October 2002; accepted 28 January 2003)


Abstract: We estimated the source parameters of 53 aftershocks (2.5 £ ML £ 4.1) of the October 1, 1995 Dinar earthquake in southwestern Turkey. Focal depths and hypocentral distances of the aftershocks range from 5 km to 15 km and 6 km to 30 km respectively, and a circular source model (Brune, 1970) is used in the analysis of S-wave displacement spectra. Although it was a moderately strong earthquake (ML = 6.0, MW = 6.2) the main shock and its moderately strong aftershocks perished nearly 90 people and damaged about 4500 buildings, mainly because of poor ground conditions. Our study revealed that the seismic moment, source radius, and stress drop of the aftershocks range in the following intervals: 7.35E+19 £ M0 £ 3.35E+22, 0.15 £ r £ 0.57 km, 5.13 £ Ds £ 100.09 bars respectively. For earthquakes of M0 < 1.0E+21 the corner frequency does not increase with decreasing seismic moment, and the stress drop shows a step near to M0 » 1.0E+21 The spectra have been affected from the attenuation only at high frequencies. The S-wave spectra have been significantly affected from the soil conditions underlying the receivers.


Key words: Source parameters, Dinar earthquake, attenuation, site effect