| Titre | Intraslab stresses in the Cascadia Subduction Zone from inversion of earthquake focal mechanisms |
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| Auteur | Wada, I; Mazzotti, S ; Wang, K |
| Source | Bulletin of the Seismological Society of America vol. 100, no. 5A, 2010 p. 2002-2013, https://doi.org/10.1785/0120090349 |
| Image |  |
| Année | 2010 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20090087 |
| Éditeur | Seismological Society of America (SSA) |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1785/0120090349 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Région extracotière de l'ouest |
| Lat/Long OENS | -130.0000 -122.0000 50.0000 40.0000 |
| Sujets | tectonique de plaques; milieux tectoniques; cadre tectonique; interprétations tectoniques; secousses séismiques; mécanismes de tremblement de terre; risque de tremblement de terre; études séismiques;
détermination des contraintes; Zone de subduction de Cascadia ; Plaque de Juan de Fuca; Plaque du Pacifique; Plaque d'Explorer ; Faille de Blanco ; tectonique; géophysique |
| Illustrations | cartes de localisation; diagrammes stéréographiques tournant de wulff; graphiques |
| Programme | Réduction des risques dus aux aléas naturels |
| Diffusé | 2010 09 20 |
| Résumé | (disponible en anglais seulement)
At the Cascadia subduction zone, intraslab earthquakes occur mostly in the northern part of the margin and its southern end, the Mendocino triple junction
(MTJ). We determine intraslab stress orientations by inverting earthquake focal mechanisms and develop working hypotheses to explain the inferred intraslab stresses and observed seismicity. Our inversion results show that the subducting Juan de Fuca
(JDF) slab in northern Cascadia is primarily under compression normal to the slab surface and tension in the downdip direction, most likely controlled by the net slab pull. An exception is a northernmost shallow region near the Nootka fault zone
where the state of stress is dominated by nearly east - west tension. We hypothesize that the shear force on the Nootka fault zone and margin-parallel mantle resistance to slab motion induce the east - west tension in this region. Near the MTJ,
stresses in the JDF plate are dominated by north - south compression down to about 20 km depth, consistent with a strong push by the Pacific plate from south of the Mendocino transform fault, but the deeper part of the slab shows downdip-tension,
similar to northern Cascadia. Deviatoric stresses in the JDF slab appear to be very low, resulting in very low intraslab seismicity. In comparison with northern Cascadia, the stresses in most of southern Cascadia are even lower, resulting in nearly
no intraslab seismicity. |
| GEOSCAN ID | 247435 |
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