Microseismic Constraints on the Mechanical State of the North Anatolian Fault Zone 13 Years After the 1999 M7.4 Izmit Earthquake

The 17 August 1999 Mw7.4 Izmit earthquake ruptured the western section of North Anatolian Fault Zone and strongly altered fault zone properties stress field. Consequences co- post-seismic changes were seen in spatio-temporal evolution seismicity surface slip rates. Thirteen years after earthquake, 2012, seismic network Dense Array for Anatolia (DANA) was deployed 1.5 years. We built a new catalog microseismicity (M < 2) by applying our automated detection location method to DANA data set. Our combines systematic backprojection wavefield template matching. analyzed statistical computing Gutenberg-Richter b-value quantifying amount temporal clustering groups nearby earthquakes. found that mainly occurs off main most active regions are Lake Sapanca step-over near Akyazi fault. Based on previous studies, we interpreted b-values (a) as indicating is occurring high background stresses driven residual stresses, (b) suggesting evidence an intricate combination aseismic taking place heterogeneous faults at eastern Sapanca, brittle-ductile transition. Combined with geodetic enhanced north-south extension around following supports possibility slow depth step-over.