Temporal variations in the fractal properties of seismicity in the North Anatolian Fault Zone between 31 degrees E and 41 degrees E

Abstract

We investigate the nature of temporal variations in the statistical properties of seismicity associated with the North Anatolian Fault Zone between longitudes 31 degrees-41 degrees E during the instrumental period 1900-1992. Temporal variations in the seismic b value and the fractal (correlation) dimension D-c of earthquake epicenters are examined for earthquakes of magnitude M(S) greater than or equal to 4.5, using sliding windows of 100 consecutive events. b varies temporally between 0.6 and 1.0, and D-c between 0.6 and 1.4, both representing significant fluctuations above the errors in measurement technique. A strong negative correlation (r = -0.85) is observed between b and D-c, consistent with previous observation of seismicity in Japan and southern California. Major events early in this century (M(S) greater than or equal to 7) are associated with low b and high D-c, respectively consistent with greater stress intensity and greater spatial clustering of epicenters-both implying a greater degree of stress concentration at this time.