HR: 0800h
AN: T11B-1261    [Abstracts]
TI: Remote Triggering of Deep Earthquakes - Indication for Criticality of Subducted Slabs
AU: * Riedel, M R
EM: miker@geo.uni-potsdam.de
AF: Institute of Geosciences, University of Potsdam, Karl-Liebknecht-Str. 24/25, Golm, D-14476 Germany
AU: Tibi, R
EM: tibi@seismo.wustl.edu
AF: Department of Earth and Planetary Sciences, Washington University, One Brookings Drive, St. Louis, MO 63130 United States
AB: Recent findings by Tibi et al. (2003) show that deep-focus earthquakes can dynamicly trigger further events in a subduction zone below 400 km depth at remote distances. The detailed analysis of 19 August 2002 Tonga deep earthquake sequences reveals evidence for both static and dynamic triggering. Based on their data, Tibi et al. propose that the triggered events are caused by transient effects in regions near criticality, where earthquakes have otherwise - without external influences - difficulty to nucleate. Here, we investigate the observed remote triggering of deep-focus earthquakes at the transition zone with a visco-elastic block slider model for ductile instabilities (Riedel, 2003). It shows, that the proposed triggering effect may be explained with a divergence of the correlation length of the stress transfer function near to "criticality", i.e. near to a critical unstable state of the subducting slab, where nucleation of ductile instabilities is prone to occur. The existence of this critical state in the deforming subducted slab is either caused by large bending forces in the mantle transition zone or, alternatively, is largely promoted by an anomaly in the slab viscosity structure resulting from a metastable delay of the olivine-spinel phase transformation (Karato et al., 2001). References S. Karato, M. R. Riedel, D. A. Yuen, "Rheological Structure and Deformation of Subducted Slabs in the Mantle Transition Zone: Implications for Mantle Circulation and Deep Earthquakes", Phys. Earth Planet. Inter. 127 (2001) 83-108 M. R. Riedel, "Modeling shear instabilities with block sliders: brittle and ductile", AGU fall meeting, San Francisco, USA (2003) R. Tibi, D. A. Wiens and H. Inoue, "Remote triggering of deep earthquakes in the 2002 Tonga sequences", Nature 424 (2003) 921-925
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8160 Rheology--general
DE: 2753 Numerical modeling
DE: 3220 Nonlinear dynamics
DE: 1236 Rheology of the lithosphere and mantle (8160)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting