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TitreThere is no pure P- or S-wave land seismic source
AuteurPugin, A; Yilmaz, O
SourceSociety of Exploration Geophysicists, Annual International Meeting, Abstracts p. 5162-5166,
Séries alt.Ressources naturelles Canada, Contribution externe 20170376
ÉditeurSociety of Exploration Geophysicists
RéunionSociety of Exploration Geophysicists 87th Annual Meeting; Houston; US; Septembre 24-29, 2017
Mediapapier; en ligne; numérique
Sujetsinterpretations sismiques; données sismiques; levés sismiques; sismicité; géophones; levés de reflexion sismiques; ondes transversales; ondes P; ondes sismiques; tectonique
Illustrationsdigrams; seismic profiles
ProgrammeCaractéristiques d'aquifères et support cartographique, Géoscience des eaux souterraines
Résumé(disponible en anglais seulement)
We conducted a field experiment at a soil site near Ottawa and recorded 9-C seismic data using a hand-held hammer and a receiver cable with 48 3-C 28-Hz geophones at 0.75-m intervals. The receiver spread length is 35.75 m and the near-offset is 0.75 m. We recorded three triplets of shot records with the impact source in vertical, inline horizontal, and crossline horizontal orientations. We identified several wave modes in the nine field records --- PP, PS, SP, and SS reflections, in addition to refracted waves. We then performed vertical sum of the three records associated with each of the three different source orientations (vertical, inline horizontal, and crossline horizontal) but with common geophone orientation, and computed the semblance spectra of the composite records. We ascertained the wave modes based on the semblance peaks.
This field test led to several important observations regarding characteristics of wave propagation in the nearsurface. First and foremost, based on our experience in using impulsive and vibroseis sources, there is no pure P- or S-wave land seismic source --- any source type can generate any combination of wave modes. Second, a wave mode may not be present in a record acquired with a given source-receiver orientation which theoretically should give rise to that mode, but can appear unexpectedly in a record acquired with a given source-receiver orientation which theoretically should not give rise to that mode. Third, the combination of wave modes captured by a specific sourcereceiver orientation depends on the Vp/Vs ratio. Finally, these observations led to a realization that for a complete
representation of the wavefield propagating within the nearsurface, we need to record multicomponent data.
Résumé(Résumé en langage clair et simple, non publié)
Cet abstract montre une nouvelle methode sismique qui a le potential d'ameliorer la qualite de l'imagerie geophysique de la terre avec des meilleures applications possibles dans les etudes environmentales et du secteur de l'energie