HR: 0800h
AN: T31A-0273    [Abstracts]
TI: Assessment of Double Benioff Zone Layer Separations Using a Modified JHD Method
AU: * Lin, G
EM: glin@geology.wisc.edu
AF: University of Wisconsin-Madison, 1215 W. Dayton St., Madison, WI 53706,
AU: Thurber, C
EM: clifft@geology.wisc.edu
AF: University of Wisconsin-Madison, 1215 W. Dayton St., Madison, WI 53706,
AU: Brudzinski, M
EM: brudzimr@muohio.edu
AF: Miami University of Ohio, 114 Shideler Hall, Oxford, OH 45056,
AB: We apply a modified joint hypocenter determination (JHD) method to relocate intermediate-depth events in order to revisit a global assessment of Double Benioff Zone (DBZ) layer separations. We analyze events from the EHB catalog for the slab segments in Brudzinski et al. (2007), including Nazca, Alaska, Aleutians, Central America, Kurile-Kamchatka, etc. The modified JHD algorithm computes arrival time residuals for each source-receiver pair for a given phase, which could be first arrivals, depth phases or converted phases, and solves for station corrections for each station. The inclusion of more phases, especially depth phases, during relocation significantly stabilizes the location process and improves the relative location accuracy. The relocated events yield improved estimates for the separation between the two DBZ layers. Brudzinski et al. (2007) found the separation to be highly correlated with subducting slab age, and generally consistent with antigorite dehydration as the mechanism responsible for the intermediate-depth seismicity. Our initial results suggest that the layer separation may be underestimated for some of the younger slabs, implying that chlorite dehydration may also play a role in intermediate-depth earthquake generation in younger slabs.
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7218 Lithosphere (1236)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting