HR: 0800h
AN: G21A-0121    [Abstracts]
TI: The 2004 Cascadia Slow Earthquake
AU: * Melbourne, T I
EM: tim@geology.cwu.edu
AF: Geodesy Laboratory & PANGA Data Analysis Facility, Department of Geological Sciences Central Washington University, 98926, WA 98926 United States
AU: Miller, M M
EM: meghan@geology.cwu.edu
AF: Geodesy Laboratory & PANGA Data Analysis Facility, Department of Geological Sciences Central Washington University, 98926, WA 98926 United States
AU: Santillan, V M
EM: marcelo@geology.cwu.edu
AF: Geodesy Laboratory & PANGA Data Analysis Facility, Department of Geological Sciences Central Washington University, 98926, WA 98926 United States
AU: Szeliga, W M
EM: walter@geology.cwu.edu
AF: Geodesy Laboratory & PANGA Data Analysis Facility, Department of Geological Sciences Central Washington University, 98926, WA 98926 United States
AB: Three years ago, continuous Global Positioning System observations revealed the stunning periodicity of recurring silent earthquakes along the Cascadia subduction zone, observed at stations that surround Puget Sound and the Straits of Georgia in the region near Seattle, Wa. and Victoria, B.C. These events are now recognized to be more widespread and occur at different frequencies in different regions along the length of the subduction zone. This results in sporadic or partial histories of creep events in intervening areas, some of which are only sparsely monitored. The frequency and timing of events in the Puget Lowlands supported a prediction that the 2004 event would occur during the late spring or early summer. Displacements in southern Washington were observed first, and propagated to the northern Puget Lowlands by mid-year. Alternatively, southern Washington sometimes appears to act in concert with events that are evident in Oregon and out of phase with the Puget Lowlands events; thus this could also be interpreted as a separate event on the southern flank of the arch in the down going slab. The displacements of individual GPS stations yield a coherent displacement field that shows episodic extension across the fore-arc region. The motion is sub-parallel to and in the opposite direction from the plate convergence motion and consistent with elastic recovery of strain caused by a discrete creep event along the plate interface.
UR: http://www.geodesy.cwu.edu
DE: 1208 Crustal movements--intraplate (8110)
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 1247 Terrestrial reference systems
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting