HR: 16:00h
AN: S52K-01    [PDF]
TI: Seismic Constraints on Mechanisms of Deep Earthquake Rupture
AU: * Estabrook, C H
EM: charles.estabrook@ctbto.org
AF: Comprehensive Nuclear-Test-Ban Treaty Organization, P.O. Box 1200, Vienna, A-1010 Austria
AB: Observations of the depth distribution of seismicity suggest that several mechanisms cause deep earthquakes. Cold subducting slabs exhibit a broad peak in seismicity between 300 and 530 kilometers depth that is best explained by transformational faulting of metastable olivine. Cumulative seismic moment release increases sharply at about 530 km depth in both cold and warm slabs, implying that events deeper than this are controlled by an equilibrium rather than a metastable phase change, which would be temperature dependent. This, together with the observation that deep seismicity predominates near the garnet-rich upper boundary of the subducting plate (former oceanic crust), suggests that the transformation of garnet to perovskite, which may release considerable water, is integral in the cause of earthquakes deeper than 530 km, where most deep earthquakes occur.
DE: 7209 Earthquake dynamics and mechanics
DE: 7218 Lithosphere and upper mantle
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8123 Dynamics, seismotectonics
DE: 8124 Earth's interior--composition and state (old 8105)
SC: Seismology [S]
MN: 2003 Fall Meeting