HR: 0800h
AN: NG31B-0879    [Abstracts]
TI: Cascadia Slow Earthquakes: Strategies for Time Independent Inversion of Displacement Fields
AU: * Szeliga, W M
EM: walter@geology.cwu.edu
AU: Melbourne, T I
AU: Miller, M M
AU: Santillan, V M
AB: Continuous observations using Global Positioning System geodesy (CGPS) have revealed periodic slow or silent earthquakes along the Cascadia subduction zone with a spectrum of timing and periodicity. These creep events perturb time series of GPS observations and yield coherent displacement fields that relate to the extent and magnitude of fault displacement. In this study, time independent inversions of the surface displacement fields that accompany eight slow earthquakes characterize slip distributions along the plate interface for each event. The inversions employed in this study utilize Okada's elastic dislocation model and a non- negative least squares approach. Methodologies for optimizing the slip distribution smoothing parameter for a particular station distribution have also been investigated, significantly reducing the number of possible slip distributions and the range of estimates for total moment release for each event. The discretized slip distribution calculated for multiple creep events identifies areas of the Cascadia plate interface where slip persistently recurs. The current hypothesis, that slow earthquakes are modulated by forced fluid flow, leads to the possibility that some regions of the Cascadia plate interface may display fault patches preferentially exploited by fluid flow. Thus, the identification of regions of the plate interface that repeatedly slip during slow events may yield important information regarding the identification of these fluid pathways.
DE: 3210 Modeling
DE: 3260 Inverse theory
DE: 1206 Crustal movements--interplate (8155)
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting