HR: 14:10h
AN: S42G-03    [PDF]
TI: Duration and Extent of the 2003 Cascadia Slow Earthquake
AU: * Melbourne, T
EM: tim@geophysics.cwu.edu
AF: Dept. of Geological Sciences, Central Washington University, Ellensburg, WA 98926 United States
AU: Miller, M
EM: meghan@geology.cwu.edu
AF: Dept. of Geological Sciences, Central Washington University, Ellensburg, WA 98926 United States
AU: Santillan, V M
EM: marcelo@geology.cwu.edu
AF: Dept. of Geological Sciences, Central Washington University, Ellensburg, WA 98926 United States
AU: Sumner, W
EM: sumner@geology.cwu.edu
AF: Dept. of Geological Sciences, Central Washington University, Ellensburg, WA 98926 United States
AU: Szeliga, W
EM: walter@geology.cwu.edu
AF: Dept. of Geological Sciences, Central Washington University, Ellensburg, WA 98926 United States
AB: Time-dependent inversion of continuous GPS measurements that capture the 2003 Cascadia slow earthquake, for which the most spatially dense observations to date are available, shows this to be the largest of 9 transients recognized to date in the Pacific Northwest and demonstrates that neither initiation nor propagation are confined specifically to the Juan de Fuca arch. The 2003 slow transient nucleated in early January of 2002 beneath the southern Puget Basin, a region south of all previously recognized transients. By March of 2003, rupture had propagated bi-laterally ~250 km to the south and north, reaching as far as the Oregon border to the south and British Columbia, Canada to the north. In total it is recognized on 12 continuous geodetic-grade GPS stations that together form a spatially coherent, N-S propagating pattern of transient reversal from secular fore-arc-normal compression to extension. The total duration and along-strike extent of this event are three months and ~500 km, respectively. The great spatial extent of this event, in conjunction with deep tremor correlated with the onset of slow faulting, suggests a high level of fluid permeability over great distances along the critically held deeper Cascadia interface. Moreover, faulting in southernmost Washington state suggests that the dearth of similar transients reported across the remainder of Cascadia reflect more a lack of sufficient instrumentation than a genuine lack of transients. EarthScope will remedy this situation in the near future.
UR: http://www.geodesy.cwu.edu/
DE: 1709 Geodesy
DE: 7209 Earthquake dynamics and mechanics
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2003 Fall Meeting