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TitrePossible interactions between the 2012 Mw 7.8 Haida Gwaii subduction earthquake and the transform Queen Charlotte Fault
AuteurHobbs, T; Cassidy, J; Dosso, S
SourceAmerican Geophysical Union Annual Fall Meeting, abstracts; par American Geophysical Union; 19192, 2014 p. 1
LiensOnline - En ligne
Année2014
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140160
ÉditeurAmerican Geophysical Union
RéunionAmerican Geophysical Union Annual Fall Meeting; San Francisco; US; décembre 15-19, 2014
Documentlivre
Lang.anglais
Medianumérique; en ligne
Formatshtml
ProvinceColombie-Britannique; Région extracotière de l'ouest
SNRC103
Lat/Long OENS-136.0000 -128.0000 56.0000 52.0000
Sujetssecousses séismiques; mécanismes de tremblement de terre; études séismiques; subduction; zones de subduction; analyses structurales; caractéristiques structurales; failles; failles transformantes; géophysique; géologie structurale
ProgrammeOuest du Canada, risque géoscience, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
This paper examines the effect of the October 2012 Mw 7.8 Haida Gwaii earthquake on aftershock nodal planes and the neighboring Queen Charlotte Fault (QCF) through Coulomb modeling and directivity analysis. The Haida Gwaii earthquake was the largest thrust event recorded in this region and ruptured an area of ~150 by 40 km on a gently NE-dipping fault off the west coast of Moresby Island, British Columbia. It is particularly interesting as it is located just to the west of the QCF, the predominantly right-lateral strike-slip fault separating the Pacific and North American plates. The QCF was the site of the largest recorded earthquake in Canada: the 1949 Ms 8.1 strike-slip earthquake whose rupture extended as far south as this 2012 event and roughly as far north as an Mw7.5 strike slip event at Craig, Alaska, which occurred just two months later in January 2013. The 75 km long portion of the QCF south of the 1949 rupture has not had a large (M = 7) earthquake in over 116 years, representing a significant seismic gap.
Coulomb stress transfer analysis is performed using finite fault models which incorporate seismic and geodetic data. Static stress changes are projected onto aftershock nodal planes and the QCF, including an inferred southern seismic gap. We find up to 86% of aftershocks are consistent with triggering, and as high as 96% for normal faulting events. The QCF experiences static stress changes greater than the empirically-determined threshold for triggering, with positive stress changes predicted for roughly half of the seismic gap region. Added stress from the mainshock and a lack of post-mainshock events make this seismic gap a likely location for future earthquakes. Empirical Green's function and directivity analyses are also performed to constrain rupture kinematics of the mainshock using systematic azimuthal variations in relative source time functions. Results indicate rupture progressed mainly to the northwest within 15o of the direction of the 2013 Craig epicenter, with at least two sources of significant moment release. These results explain observed surface wave amplification at Alaskan seismic stations and support the idea that strong surface wave shaking may be linked to the possible delayed triggering of the Mw 7.5 Craig event, through an unknown intermediate mechanism that accounts for the two-month hiatus.
Résumé(Résumé en langage clair et simple, non publié)
Le Octobre 2012 tremblement de terre de magnitude 7,8 a entraîné jusqu'à 4 m de déplacement le long d'une faille non comptabilisé antérieurement large de la côte ouest de Haida Gwaii. Mouvement long de la faille s'étendait sur plus de 100-km le long de la côte et s'étend sur environ 50 km au large des côtes. Ce mouvement très important des roches a changé le champ de contraintes dans la région de Haida Gwaii (y compris le long de la faille de la Reine Charlotte). Dans cette étude, nous calculons les changements dans le domaine du stress associé au séisme Haida Gwaii 2012 et constatons que la plupart des répliques tombent en mer dans la région de prédire le changement de contrainte maximale. En outre, nous avons constaté que le stress supplémentaire a été ajoutée à la faille de la Reine-Charlotte à proximité - y compris un segment qui est considéré comme une "lacune sismique», comme il n'a pas connu un tremblement de terre au cours des temps historiques. Cette étude aide à améliorer nos modèles de risque de tremblement de terre de cette région.
GEOSCAN ID295089