Spatial and Temporal Distribution of B and P Values of 12 November 1999 Düzce Earthquake Estimated From Its Aftershocks and Assessments for Future Earthquake Hazard

Abstract

It has been well established both in laboratory and case studies that b value of frequency-magnitude relationship of earthquake statistics is inversely related to the stress in the earth's crust. In this study, spatial and temporal distribution of b values and aftershock decay parameter p are mapped along the rupture plane of the Düzce earthquake of 12 November 1999 and neighbouring fault segments both on earth surface and in depth domain from the aftershock seismicity of the earthquake utilizing a software package. It was obtained that b values and p values are much higher along the mapped asperity over the Düzce fault (b=1.2-1.5, p=1-1.3) indicating a possible stress release, while lower b values prevailing along the Karadere fault segment (b=0.8-1.0, p=0.7-0.8) and Elmalik (b=1.1-1.2, p=1.1) fault indicating a possible stress loading. Since the Karadere fault segment is ruptured during the Kocaeli earthquake of 17 August 1999 and there is no information available for a notable earthquake on the Elmalik fault in the last century, it can be speculated that seismic risk on the Elmalik fault has increased after the 1999 Düzce earthquake.