Regional moment tensor inversion for strong aftershocks of the August 17, 1999 Izmit earthquake (M-w=7.4)

We analyzed the source mechanisms of the thirty largest aftershocks (4.0 le ss than or equal toM(L)less than or equal to6.2) of the August 17, 1999 Izm it earthquake (M-w=7.4) by applying the Regional Moment Tensor inversion me thod using data from near-regional broadband stations. The inversion soluti ons were compared to 17 well-constrained first motion solutions, and were s een to be in good agreement. We found that the dominance of strike-slip mot ion is the main characteristic of the Izmit earthquake sequence. Significan t aftershock activity was recorded to the west and east of the un-ruptured extremities. In the east the aftershocks located near the town of Duzce rep resent an early replica of the November 12, 1999 Duzce earthquake (M-w=7.2) in terms of locations and source mechanisms. In the Marmara Sea, where the fault geometry is still very poorly resolved, most aftershocks have right lateral strike slip solutions with strike direction parallel to the submerg ed branches of the North Anatolian Fault.