HR: 14:40h
AN: G43A-04    [Abstracts]
TI: Kinematics and temporal evoluation of silent earthquakes along the Cascadia convergent margin
AU: * Miller, M M
EM: meghan@geology.cwu.edu
AF: Geodesy Laboratory, Department of Geological Sciences 400 E. University Avenue Central Washington University, Ellensburg, WA 98926 United States
AU: Melbourne, T I
EM: tim@geology.cwu.edu
AF: Geodesy Laboratory, Department of Geological Sciences 400 E. University Avenue Central Washington University, Ellensburg, WA 98926 United States
AU: Santillan, V M
EM: marcelo@geology.cwu.edu
AF: Geodesy Laboratory, Department of Geological Sciences 400 E. University Avenue Central Washington University, Ellensburg, WA 98926 United States
AU: Szeliga, W
EM: walter@geology.cwu.edu
AF: Geodesy Laboratory, Department of Geological Sciences 400 E. University Avenue Central Washington University, Ellensburg, WA 98926 United States
AB: High-precision, continuous GPS geodesy in the Pacific Northwest reveals a rich history of transient deformation along the Cascadia subduction zone, where the fault is in transition from fully coupled to freely slipping. The spatial and temporal pattern of transient deformation reveals inner fore-arc areas where creep events originate with startling periodicity: northern Vancouver Island, the Puget Lowlands, and northernmost California. These events are typified by surface displacement fields with up to 5-8 mm, in spatially coherent patterns consistent with elastic recovery of modest convergence parallel motion along the jerking plate interface. In the Puget Lowlands, where GPS station coverage is dense, the events typically originate in Puget Sound and propagate laterally, either unilaterally or bilaterally, as well as up-dip. While the displacement field, propagation patterns, and moment vary among events in each of the three source areas, the periodicity of silent earthquakes is regular near its initiation point. The two northerly areas each experience 14-month periodicity, but are out of phase; the southern area experiences 11-month periodicity, and thus goes in and out of phase with events to the north. Intervening areas have sparse station coverage. Where good time series are available from intervening areas, however, they appear to record interfering deformation fields from sporadic propagation of events adjacent source areas along strike. Such stations record a partial and irregular composite displacement history from events initiated in each direction. The temporal and spatial patterns of these events points to their fundamental role in the Cascadia subduction zone earthquake cycle.
UR: http://www.geodesy.cwu.edu
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Geodesy [G]
MN: Fall Meeting 2005