HR: 13:40h
AN: S42G-01    [PDF]
TI: The north Cascadia Episodic Tremor and Slip (ETS) Event of February and March 2003
AU: * Rogers, G
EM: rogers@pgc.nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre, P.O. Box 6000, Sidney, BC V8L 4B2 Canada
AU: Dragert, H
EM: dragert@pgc.nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre, P.O. Box 6000, Sidney, BC V8L 4B2 Canada
AU: Cassidy, J
EM: cassidy@pgc.nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre, P.O. Box 6000, Sidney, BC V8L 4B2 Canada
AU: Kao, H
EM: kao@pgc.nrcan.gc.ca
AF: Geological Survey of Canada, Pacific Geoscience Centre, P.O. Box 6000, Sidney, BC V8L 4B2 Canada
AB: Repeated slip has been detected on the deep interface of the northern Cascadia subduction zone by observing surface deformation on a network of continuous Global Positioning System sites. These slip events have now been found to have, accompanying tremor-like, non-earthquake, seismic signatures. The tremor is mainly shear wave energy concentrated in a bandwidth of 1-5Hz. We refer to this associated tremor and slip phenomena as Episodic Tremor and Slip (ETS). From the regular 13 to 16 month recurrence times of the previous five ETS events identified beneath southern Vancouver Island since 1996, an ETS event was expected in the region early in 2003. The seismograph and GPS networks operated by the Geological Survey of Canada were supplemented with additional stations to ensure that the seismic and deformation signature of the expected ETS event were well recorded. The first ETS tremors started on February 25 just south of Victoria, British Columbia in the region of the International border. Within a few days, slip was confirmed by southwest displacements at continuous GPS stations in the vicinity of Victoria. The source locations of tremor and slip migrated northwest about 150 km, traversing the southern third of Vancouver Island. The last tremor signal of the sequence was detected on March 26. Tremors emanated from a region on, or very close to, the subduction interface between the two lithospheric plates. They were confined to a band about 50km wide, consistent with the region of the modelled slip, just down dip from the proposed locked zone on the subduction interface.
DE: 7223 Seismic hazard assessment and prediction
DE: 8150 Plate boundary--general (3040)
SC: Seismology [S]
MN: 2003 Fall Meeting