title: Extended nucleation of the 1999 Mw 7.6 Izmit earthquake.
abstract: Laboratory and theoretical studies suggest that earthquakes are preceded by a phase of developing slip instability in which the fault slips slowly before accelerating to dynamic rupture. We report here that one of the best-recorded large earthquakes to date, the 1999 moment magnitude (M(w)) 7.6 Izmit (Turkey) earthquake, was preceded by a seismic signal of long duration that originated from the hypocenter. The signal consisted of a succession of repetitive seismic bursts, accelerating with time, and increased low-frequency seismic noise. These observations show that the earthquake was preceded for 44 minutes by a phase of slow slip occurring at the base of the brittle crust. This slip accelerated slowly initially, and then rapidly accelerated in the 2 minutes preceding the earthquake.
authors.affiliation: Centre National de la Recherche Scientifique and Université Joseph Fourier, Grenoble, France. Michel.Bouchon@ujf-grenoble.fr
authors.forename: Michel
authors.initials: M
authors.lastname: Bouchon
authors.forename: Hayrullah
authors.initials: H
authors.lastname: Karabulut
authors.forename: Mustafa
authors.initials: M
authors.lastname: Aktar
authors.forename: Serdar
authors.initials: S
authors.lastname: Ozalaybey
authors.forename: Jean
authors.initials: J
authors.lastname: Schmittbuhl
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Bouin