HR: 10:50h
AN: T42A-03    [Abstracts]
TI: Global Double Benioff Zone Prevalence and Characteristics through Statistical Estimates of Slab-Normal Distribution
AU: Thurber, C H
EM: clifft@geology.wisc.edu
AF: Univeristy of Wisconsin, Department of Geology and Geophysics 1215 W. Dayton St., Madison, WI 53706 United States
AU: * Brudzinski, M R
EM: brudzimr@muohio.edu
AF: Miami University, Department of Geology 114 Shideler, Oxford, OH 45056 United States
AU: Engdahl, E R
EM: engdahl@armstrong.colorado.edu
AF: University of Colorado, Department of Physics 390 UCB, Boulder, CO 80309 United States
AU: DeShon, H R
EM: hdeshon@geology.wisc.edu
AF: Univeristy of Wisconsin, Department of Geology and Geophysics 1215 W. Dayton St., Madison, WI 53706 United States
AB: In subduction zones, inclined Wadati-Benioff zones of seismicity occur within the subducting lithosphere and thus can be used to examine the structure of downgoing slabs. A particularly detailed set of information about the slab can be obtained from Double Benioff Zones (DBZs), where two sub-parallel planes of seismicity are separated in depth by as much as 30 km. Based on a handful of observations of DBZs, the planes have been proposed to mark the location of petrologic dehydration reactions, which could in turn trigger earthquakes via dehydration embrittlement. Identification of DBZs has typically been limited to areas where dense local networks cover the subduction zone, but recent discoveries of DBZs in regions without local networks like Java warrant a more global investigation of DBZ prevalence. We have developed a straightforward method for determining the separation between layers of a DBZ that can also be used to assess the existence of a DBZ. This technique determines the statistical distribution of events within the DBZ in the slab-normal direction. We will present results from applying this method to both global and regional datasets, including an objective evaluation of the improvement in DBZ characterization using hypocentral relocations and focal depth refinement techniques. Patterns in the geographic distribution of DBZ prevalence will be analyzed, as well as relationships between layer separation and subducting plate properties with special attention to thermal parameters. Determining the overall prevalence and regularity of DBZs on a global basis is necessary to understand the conditions, both seismic and petrologic, in the evolution of subducting slabs.
DE: 3200 MATHEMATICAL GEOPHYSICS (0500, 4400, 7833)
DE: 3613 Subduction zone processes (1031, 3060, 8170, 8413)
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7215 Earthquake source observations (1240)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Tectonophysics [T]
MN: Fall Meeting 2005