Analysis of Izmit Aftershocks: Spatial and temporal changes in seismicity parameters and stress tensor inversion of Izmit aftershocks

Spatial and temporal clustering of 10066 aftershocks are investigated along the 17 August 1999 Izmit (Mw = 7.4) earthquake rupture zone with a total length of 140 km. Based on the combined analysis of b- and p-values three asperities along the Izmit rupture of the North Anatolian Fault Zone are identified namely east of Sapanca Lake, west of Karadere-Düzce and east of Karadere-Düzce regions. Aftershock focal mechanisms are investigated along the eastern part of the 17 August 1999 Izmit earthquake (Mw = 7.4) rupture zone during the time window 22 August 1999 – 17 October 1999. The Karadere Fault reflects a combined strike-slip/normal faulting regime, the Düzce Basin that also has led the forthcoming Mw 7.2 mainshock 87 days later shows NE-SW extensional normal faulting.

Izmit aftershock epicenters (black dots) along the rupture of the mainshock. The seismic stations are included [21 GTF (red) and 15 SABONET (yellow)]. For reference, the Izmit Mw = 7.4 and the Düzce Mw = 7.2 strike-slip focal mechanisms are plotted
Izmit aftershock epicenters (black dots) along the rupture of the mainshock. The seismic stations are included [21 GTF (red) and 15 SABONET (yellow)]. For reference, the Izmit Mw = 7.4 and the Düzce Mw = 7.2 strike-slip focal mechanisms are plotted