| Titre | Tectonic tremor localization using Bayesian inversion |
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| Auteur | Bombardier, M; Cassidy, J F ; Dosso, S E; Kao, H |
| Source | Seismological Research Letters vol. 93, no. 2B, 2022 p. 1363 |
| Image |  |
| Année | 2022 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20210551 |
| Éditeur | Seismological Society of America |
| Document | publication en série |
| Lang. | anglais |
| Media | papier; numérique; en ligne |
| Formats | pdf |
| Province | Colombie-Britannique |
| SNRC | 92B |
| Lat/Long OENS | -124.0000 -122.0000 49.0000 48.0000 |
| Sujets | secousses séismiques; Nothern Cascadie; tectonique |
| Programme | Géoscience pour la sécurité publique Risques géologique du tremblement de terre |
| Diffusé | 2022 04 19 |
| Résumé | (disponible en anglais seulement)
Periodically-occurring slow earthquakes in northern Cascadia produce low frequency seismic signals including low-frequency earthquakes (LFEs) and tectonic
tremor. Methods to locate the sources of these two types of events often yield results that do not coincide but both are thought to originate near the subduction interface. As such, whether LFEs and tremor result from the same processes and where
those processes are located remain open questions. In this study, we produce a catalogue of tremor sources from an episodic tremor and slip (ETS) event beneath Vancouver Island, Canada, using a new location method. Our method includes processes that
automatically detect tremor signals, construct datasets using waveform-envelope cross-correlation, remove outliers, estimate data error statistics and use a grid-based Bayesian inversion to locate source positions and quantify uncertainties from the
resulting 3D probability distributions. We first test this method on local crustal earthquakes and obtain well constrained relocations within an average of 3.5 km in epicenter and 4.5 km in depth of official catalog values. We then locate tremor
during the November 2019 ETS event and find that source epicenters are highly clustered with rapid migration between clustered patches. Consistent with other studies, we show source depths peak at ~30 km depth, which is 10 km shallower than current
slab surface models and LFE locations. The relatively shallow and distributed depths of well-constrained tremor sources suggest either that ETS slip occurs within a shallow vertically-distributed shear zone or that a significant portion of tremor is
produced in the lower continental crust. Additionally, the shallower occurrence of tremor relative to LFEs suggests different source processes. Application of our location technique to additional ETS events will help to better understand the
locations of tremor sources and thereby infer potential physical processes of ETS tremor generation. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Cette étude utilise une technique de localisation améliorée pour localiser plus précisément les tremblements sismiques associés aux événements
de tremblement épisodique et de glissement dans la zone de subduction de Cascadia. Il convient de noter l'amélioration de l'estimation de la profondeur qui nous permet de déterminer si ces secousses proviennent de la faille de subduction ou
d'ailleurs. La nouvelle méthode est d'abord testée sur les emplacements et les profondeurs des tremblements de terre pour tester et calibrer la technique. Nous constatons que la majorité des tremors ETS proviennent au-dessus de la plaque de
subduction (et de la faille de subduction), ce qui suggère qu'ils sont liés à des fluides et/ou des fractures dans la croûte continentale inférieure. Cette recherche fournit de nouvelles informations sur les processus physiques de génération de
tremblements ETS et contribuera à améliorer l'estimation des risques sismiques. |
| GEOSCAN ID | 329448 |
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