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.
e-mail: eyalcin@istanbul.edu.tr
(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 dyne.cm, 0.15 £
r £
0.57 km, 5.13 £ Ds £ 100.09 bars respectively. For earthquakes of M0
< 1.0E+21 dyne.cm the corner frequency does
not increase with decreasing seismic moment, and the stress drop shows a step
near to M0 » 1.0E+21 dyne.cm. 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