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TitreSeafloor seismometers monitor northern Cascadia earthquakes
AuteurScherwath, M; Spence, G; Obana, K; Kodaira, S; Wang, K; Riedel, M; McGuire, J; Collins, J
SourceEos, Transactions of the American Geophysical Union vol. 92, no. 47, 2011 p. 421-422,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110269
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'ouest; Colombie-Britannique
Lat/Long OENS-130.0000 -124.5000 50.0000 47.5000
Sujetsrangées sismiques; interpretations sismiques; zones sismiques; sismographes; sismicité; séismologie; séismologie des secousses fortes; réseau sismique; secousses séismiques; études séismiques; risque de tremblement de terre; géophysique; géologie marine
Illustrationslocation maps; profiles
ProgrammeTargeted Hazard Assessments in Western Canada, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
The Mw = 9.0 earthquake of 11 March 2011at the Japan Trench and its devastating tsunami underscore the importance of understanding seismogenic behavior of subduction faults and realistically estimating the potential size of future earthquakes and tsunamis. For the Cascadia subduction zone (Figure 1a), a critical knowledge gap is the level of microseismicity offshore, especially near the megathrust, needed to better understand the state of the locked zone. In 2010 the first detailed seafloor earthquake monitoring campaign along the northern Cascadia subduction zone recorded nearby earthquakes in the local magnitude (ML ) range from possibly around zero to 3.8 (Figures 1b and 1c) and larger earthquakes from outside this region. Preliminary analyses indicate that the network appears to have yielded a fairly complete catalog for events with ML > 1.2. Only a few tens of these events occurred beneath the continental shelf and slope (Figure 1a). The majority of the earthquakes were located along the margin-perpendicular Nootka fault zone. The relatively low seismicity away from the Nootka fault is consistent with a fully locked megathrust. Land-based GPS measurements cannot resolve the question of
whether the offshore part of the megathrust seismogenic zone is narrow and fully locked or wider and only partially locked (slowly creeping). If it were only partially locked, the seafloor seismometer data should show many more small earthquakes along the interface than were actually detected.