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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L14305, doi:10.1029/2005GL022922, 2005

Slab pull, slab weakening, and their relation to deep intra-slab seismicity

Susan L. Bilek

Earth and Environmental Science Department, New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA


Clinton P. Conrad

Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, USA


Carolina Lithgow-Bertelloni

Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, USA


Abstract

Subduction zone seismicity is highly variable. Great earthquakes occur at few subduction zones around the world, with significant variation in size and frequency of deep events. Interactions between overriding and subducting plates and slab pull strength for individual plates provide a framework for understanding these variations. Previous work suggests an inverse correlation between great earthquake moment release and the degree to which the subducted slab is connected to the surface plate. We find positive correlations between degree of plate-slab attachment and moment release from intermediate and deep earthquakes. This implies that shallow slab weakening that occurs at trenches where compressive stresses (and great earthquakes) dominate not only detaches slabs from plates, but is maintained as the slab descends, discouraging deep seismicity. Regions of low shallow moment release are consistent with extensional shallow stress regimes and undamaged slabs. Such slabs maintain mechanical strength during descent and deform seismogenically at depth.

Received 8 March 2005; accepted 21 June 2005; published 21 July 2005.

Index Terms: 3060 Marine Geology and Geophysics: Subduction zone processes (1031, 3613, 8170, 8413); 7240 Seismology: Subduction zones (1207, 1219, 1240); 7230 Seismology: Seismicity and tectonics (1207, 1217, 1240, 1242); 8159 Tectonophysics: Rheology: crust and lithosphere (8031); 8168 Tectonophysics: Stresses: general.

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Citation: Bilek, S. L., C. P. Conrad, and C. Lithgow-Bertelloni (2005), Slab pull, slab weakening, and their relation to deep intra-slab seismicity, Geophys. Res. Lett., 32, L14305, doi:10.1029/2005GL022922.