SPATIAL VARIATIONS OF THE FRACTAL PROPERTIES OF SEISMICITY IN THE ANATOLIAN FAULT ZONES

The Anatolian fault zones are seismically active strike-slip fault zon es transcending the Anatolian plate in E-W and N-S directions. We inve stigate the spatial variations of seismicity along these zones in an a ttempt to investigate fault complexity along strike, quantified by the Gutenberg-Richter b-value and the fractal (correlation) dimension of earthquake epicentres, using the maximum likelihood method and the cor relation integral, respectively. The investigation covers instrumental ly recorded earthquakes of magnitude M > 4.5 occurring between 1900 an d 1992. We find systematic spatial variations which may be related to structural or mechanical variability along strike. In particular the l arge change in strike at the northern apex of the North Anatolian Faul t Zone is associated with the highest correlation dimension and lowest b-value for seismicity this century. The correlation dimension and b- value show a negative correlation with respect to each other, similar to results reported in other regional studies of Japan and southern Ca lifornia. This statistical correlation is stronger when more objective seismic zoning is carried out (based on number of events) rather than more subjective seismotectonic zoning in common use in seismic hazard analysis.