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TitreSpatial-temporal patterns of seismic tremors in northern Cascadia
AuteurKao, H; Shan, S -J; Dragert, H; Rogers, G; Cassidy, J F; Wang, K; James, T; Ramachandran, K
SourceJournal of Geophysical Research vol. 111, no. B3, B03309, 2006, 17 pages, https://doi.org/10.1029/2005JB003727 (Accès ouvert)
Année2006
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 2005506
ÉditeurWiley-Blackwell
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1029/2005JB003727
Mediapapier; en ligne; numérique
Formatshtml; pdf
ProvinceColombie-Britannique
SNRC92B; 92C; 92F; 92G
Lat/Long OENS-126.0000 -122.0000 50.0000 47.5000
Sujetsséismologie; études séismiques; sismicité; ondes sismiques; sismographes; rangées sismiques; réseau sismique; tectonique de plaques; frontières de plaques; modèles; établissement de modèles; croûte continentale; déformation; analyse des déformations; détermination des contraintes; panneau orienté vers le bas; migration des fluides; mécanique des fluides; zones de cisaillement; Zone de subduction de Cascadia ; Plaque de l'Amérique du Nord; Plaque de Juan de Fuca; géophysique; Phanérozoïque; Cénozoïque; Quaternaire
Illustrationssketch maps; seismograms; graphs; time series; histograms; spectra; tables; cross-sections; profiles; models
ProgrammeLes risques naturels et les interventions en cas d'urgence
Diffusé2006 03 17
Résumé(disponible en anglais seulement)
We study in detail the two consecutive episodic tremor-and-slip (ETS) events that occurred in the northern Cascadia subduction zone during 2003 and 2004. For both sequences, the newly developed Source-Scanning Algorithm (SSA) is applied to seismic waveform data from a dense regional seismograph array to determine the precise locations and origin times of seismic tremors. In map view, the majority of the tremors occurred in a limited band bounded approximately by the surface projections of the 30 km and 50 km depth contours of the plate interface. The horizontal migration of tremor occurrence is from southeast to northwest with an average speed of 5 km/d. In cross section, tremors in both sequences span a depth range of over 40 km across the interface, with the majority occurring in the overriding continental crust. In particular, 50-55% of them are located within 2.5 km from the strong seismic reflector bands above the plate interface. The lack of vertical migration implies that a slow diffusion process in the vertical direction cannot be responsible for tremor occurrences. The source spectra of tremors clearly lack high-frequency content (>5 Hz) relative to local earthquakes. We propose two possible models to explain the relationship between slip and tremors. The first one regards ETS tremors as the manifestation of hydroseismogenic processes in response to the temporal strain variation associated with the episodic slip along the lower portion of the plate interface downdip from the locked zone. In the second model, tremors and slip are associated with the same process along the same structure in a distributed deformation zone across the plate interface. Neither model can be dismissed conclusively at this stage.
GEOSCAN ID221449