GEOSCAN, résultats de la recherche


TitreInvited review paper: Some outstanding issues in the study of great megathrust earthquakes - the Cascadia example
AuteurWang, K; Tréhu, A M
SourceJournal of Geodynamics vol. 98, 2016 p. 1-18,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20150275
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'ouest
Lat/Long OENS-128.0000 -124.0000 49.5000 40.0000
Sujetssecousses séismiques; études séismiques; mécanismes de tremblement de terre; subduction; zones de subduction; Cascadie; géophysique
Illustrationslocation maps; cross-sections; profiles
ProgrammeOuest du Canada, risque géoscience, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
Because of a combination of new observational tools and a flurry of large megathrust earthquakes,tremendous progress has been made in recent years towards understanding the process of great subduc-tion earthquakes at Cascadia and other subduction zones around the world. This review article attemptsto clarify some of widely used geodynamic concepts and identify the most important scientific questionsfor future research related to megathrust behaviour. It is important to specify how the megathrust seis-mogenic zone has been defined when comparing data and models. Observations and concepts currentlyused to define the seismogenic zone include: (A) the stability transition in rate-and-state dependent fric-tion; (B) the slip zone of large interplate earthquakes; (C) the distribution of small-medium earthquakes;and (D) the geodetically-determined zone of fault locking. Land-based geodetic measurements indicatethat the Cascadia megathrust is locked to some extent, but the degree of locking is not well constrained.The near absence of detectable interplate seismicity, with the exception of a segment near 44.5?N andnear the Mendocino Triple Junction, is presently interpreted to indicate full locking along most of Cas-cadia. Resolving the locking state requires seafloor geodetic measurements. The slip behaviour of theshallowest segment of the megathrust and its tsunamigenic potential are complex and variable. Struc-tural studies combined with modeling have the potential to improve our understanding of the signatureleft in the structure by the slip history. For several reasons, but mostly because of interseismic viscoelas-tic stress relaxation, the downdip limit of megathrust locking cannot be reliably constrained by geodeticdata. Independent information is needed on the composition and thermal state of fault zone materials.The spatial relationship between the seismogenic zone and the zone of Episodic Tremor and Slip (ETS)remains controversial. Observations from the Nankai subduction zone and the San Andreas Fault suggestthat ETS does not mark a simple spatial transition from seismic to aseismic behaviour and that multi-ple transitions may be present because of petrological and rheological changes with depth. Coseismicrupture in the AD 1700 Cascadia earthquake has been shown to vary along strike, and it is important toinvestigate whether the position of boundaries between high slip and low slip are stationary with time(and therefore probably geologically controlled) and are reflected in current interseismic locking of themegathrust.
Résumé(Résumé en langage clair et simple, non publié)
Au cours des trois dernières décennies, la communauté scientifique a réalisé des progrès remarquables dans la compréhension des processus relatifs aux séismes de méga-chevauchement à la zone de subduction de Cascadia et à d'autres zones de subduction. Toutefois, de récentes observations, particulièrement des données sur plusieurs grands séismes de méga-chevauchement, ont soulevé de nouvelles questions scientifiques. Dans cet article de synthèse, nous clarifions certains des concepts géodynamiques largement utilisés et nous déterminons les questions scientifiques les plus importantes pour les futures recherches liées au comportement d'un méga-chevauchement. Nous mettons l'accent sur les questions qui sont les plus urgentes pour améliorer l'évaluation des dangers et l'atténuation des risques.