Seismic site classification and site period mapping in the Ottawa area using geophysical methods
Notice bibliographique
Résumé
The 2005 National Building Code of Canada (2005NBCC) recommended new guidelines for construction in earthquake hazard areas. Estimated horizontal shearing forces at ground surface, resulting from a 1:2475 year return period earthquake, are in part based on the geotechnical/geophysical properties of the near surface at a particular building site. This project has demonstrated the use of geophysical techniques to map the variation of nearsurface geotechnical properties required to establish the seismic shaking properties within the City of Ottawa. Ottawa was chosen for this demonstration since: 1) it is an area of higher seismic hazard under the influence of the West Quebec and Ottawa Valley seismic zones, 2) a wide variation in soil and rock properties exist within the city limits, 3) similar site conditions occur throughout much of the Ottawa-St Lawrence Valley area, and, 4) GSC and university specialists were available locally, thus reducing field costs. Current 2005NBCC guidelines suggest estimates of average shear wave velocity to a depth of 30 m (Vs30) as a primary parameter required to estimate seismic shaking levels. Shear wave velocity measurement techniques were tested and modified for soil and rock conditions within the project area. These included: seismic refraction and reflection site evaluation (685 sites), multichannel analyses of surface waves (MASW-33 sites), downhole seismic measurements (16 boreholes), and multichannel towed seismic reflection profiling techniques (Landstreamer ~25 line-km). Shear wave velocities were measured throughout the soil column (to depths of 100+ m); in addition, shear wave velocities were measured for the differing rock types within the city. Within the survey area, a borehole geology data bank consisting of approximately 21900 entries was re-analysed in terms of shear wave velocity-depth structure based on the field shear wave velocity measurements. A map of the variation of Vs30 was developed from the integration of all borehole and shear wave velocity data. The map shows that low Vs30 values (associated with higher shaking levels) occur in areas where thick soft soils occur. A second map of fundamental site periods was developed from the measurement of both soil seismic properties and depth to bedrock. Estimates of such natural resonant periods of the ground are also required as an aid in estimating the response of structures to seismic shaking. The fundamental site period map indicates that significant long period resonance is associated with areas where thick soft soils occur. Comparison of this map with approximately 200 passive seismic noise measurements (horizontal to vertical spectral ratios HVSR) indicated a well-documented systematic variance. An empirical relationship between the two measurement techniques has been developed. The main products of this research are: 1) A map of Vs30 , following the guidelines of the current 2005NBCC, 2) A map of fundamental resonance period of the soil based on measured shear wave velocities and depths to resonant impedance boundaries, and 3) A data bank (approximately 22000 points) of average shear wave velocity-depth functions including depth to bedrock, bedrock shear wave velocities and fundamental site periods. It is hoped that this information will be a useful guide for city planners, geotechnical engineers, as well as emergency planning organizations. Similar geophysical applications are possible in other areas of the Ottawa- St. Lawrence valleys in the future.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,002 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».