Evidences of instantaneous dynamic triggering during the seismic sequence of year 2000 in South Iceland

• Main Authors: Antonioli, A., Belardinelli, M. E., Bizzarri, A., Vogfjord, K. S.
• Other Authors: Antonioli, A.; University of Ulster, Belardinelli, M. E.; Settore di Geofisica, Dipartimento di Fisica, Universita' di Bologna, Bizzarri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia, Vogfjord, K. S.; Icelandic Meteorological Office, University of Ulster, Settore di Geofisica, Dipartimento di Fisica, Universita' di Bologna, Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia, Icelandic Meteorological Office
• Format: Manuscript
• Language: English
• Published: 2005
• Subjects: Stress interaction; friction laws; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability; Iceland
• Online Access: http://hdl.handle.net/2122/455

We analyze the coseismic stress perturbation during the June 17th, 2000 South Iceland seismic sequence; the mainshock (MS 6.6) was followed by three large events within few tens of seconds (8, 26, and 30 s, respectively) located within 80 km. The aim of this paper is to investigate short-term fault interaction and instantaneous triggering. This happens when a fault perturbed by a stress change fails before the end of the transient stress perturbation. We compute the shear, normal, and Coulomb stress changes as functions of time in a stratified elastic half-space by using discrete wavenumber and reflectivity methods. We calculate dynamic stresses caused by the mainshock at the hypocenters of these three subsequent events. Our numerical results show that the onset of the last two events is slightly delayed with respect to the arrival time of the second positive peak of Coulomb stress variation, while the first event occurred after the first positive stress peak. We have also analysed the response of a spring-slider system representing a fault governed by a rate- and state-dependent friction law, perturbed by shear and normal stress variations caused by the mainshock. The fault response to the computed stress perturbations is always clock advanced. We have found suitable constitutive parameters of the modelled fault that allow the instantaneous dynamic triggering of these three earthquakes. If the initial sliding velocity is comparable with the tectonic loading velocity, we obtained failure times close to the observed origin times for low values of the initial effective normal stress. Submitted open