| Titre | Azimuthal anisotropy in Bayesian surface wave tomography: application to northern Cascadia and Haida Gwaii, British Columbia |
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| Auteur | Gosselin, J M; Audet, P; Schaeffer, A J ; Darbyshire, F A; Estève, C |
| Source | Geophysical Journal International vol. 224, issue 3, 2020 p. 1724-1741, https://doi.org/10.1093/gji/ggaa561 |
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| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200680 |
| Éditeur | Oxford University Press |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1093/gji/ggaa561 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Colombie-Britannique |
| Région | Haida Gwaii; Cascadia |
| Lat/Long OENS | -140.0000 -118.0000 63.0000 40.0000 |
| Sujets | anisotropie; etudes des ondes de surface; ondes sismiques; séismologie; Sciences et technologie; tectonique |
| Illustrations | cartes de localisation; diagrammes; graphiques |
| Diffusé | 2020 11 20 |
| Résumé | (disponible en anglais seulement)
Surface wave tomography is a valuable tool for constraining azimuthal anisotropy at regional scales. However, sparse and uneven coverage of dispersion
measurements make meaningful uncertainty estimation challenging, especially when applying subjective model regularization. This paper considers azimuthal anisotropy constrained by measurements of surface wave dispersion data within a Bayesian
trans-dimensional (trans-d) tomographic inversion. A recently proposed alternative model parametrization for trans-d inversion is implemented in order to produce more realistic models than previous studies considering trans-d surface wave tomography.
The reversible-jump Markov chain Monte Carlo sampling technique is used to numerically estimate the posterior probability density of the model parameters. Isotropic and azimuthally anisotropic components of surface wave group velocity maps (and their
associated uncertainties) are estimated while avoiding model regularization and allowing model complexity to be determined by the data information content. Furthermore, data errors are treated as unknown, and solved for within the inversion. The
inversion method is applied to measurements of surface wave dispersion from regional earthquakes recorded over northern Cascadia and Haida Gwaii, a region of complex active tectonics but highly heterogeneous station coverage. Results for isotropic
group velocity are consistent with previous studies that considered the southern part of the study region over Cascadia. Azimuthal anisotropic fast-axis directions are generally margin-parallel between Vancouver Island and Haida Gwaii, with a small
change in direction and magnitude along the margin which may be attributed to the changing tectonic regime (from subduction to transform tectonics). Estimated errors on the dispersion data (solved for within the inversion) reveal a correlation
between surface wave period and the dependence of data errors on travel path length. This paper demonstrates the value of considering azimuthal anisotropy within Bayesian tomographic inversions. Furthermore, this work provides structural context for
future studies of tectonic structure and dynamics of northern Cascadia and Haida Gwaii, with the aim of improving our understanding of seismic and tsunami hazards. |
| GEOSCAN ID | 327965 |
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