Construire des modèles sphériques de Terre
Ondes P et S
Ondes P et S
Vitesse des ondes de Love
T = 40 s
T = 70 s
T = 150 s
www.geologie.ens.fr/~madariag
Tomographie globale
B. Romanowicz
Grand 2002
Tomo ondes P
vd Hilst
1998
Tomographie globale
- Séismes enregistrés depuis 1965 (100 000 événements bien localisés)
- 3 à 6000 stations utilisées
- Découpe de la Terre en cube de 0.5 à 2° (50 à 200 km) - Inversion mathématique de millions d'équations
simultanément
- Tests de résolution
- Visualisation des modèles tomographiques
Velocity
Harvard
Berkeley
Caltech
Isotropic Vs
Depth = 100 km
Maggi et al., (2005)
Interfaces du manteau
Topographie des discontinuités
Les interfaces du manteau
Les précurseurs des ondes SS (S
410S et S
660S)
séisme
station
Précurseurs de SS
Période 20 s
résolution latérale : 2000 km
(Tauzin et al., 2007) Flanagan & Shearer, 1998
Topographie des discontinuités
Flanagan & Shearer, 1998
Anisotropie
Graine
Geometry of ray paths for PKP branch.
(A) Ray paths for PKPAB (red curve), PKPBC (green curve), and PKPDF or PKIKP (blue curve) at an epicentral distance of 150°. PKPBC (BC for brevity) and PKPAB (AB) turn in the lower and upper outer core , respectively, and do not sample the inner core. Travel times of PKPDF (DF) are referred to as "absolute travel times"
in contrast to "differential travel times,"
which are obtained by subtracting DF travel times from BC (BC – DF) or AB (AB – DF) travel times. Differential travel times are often used in inner-core studies because similarity of the BC or AB path with DF path within the mantle reduces undesirable mantle and earthquake effects from the data. Mantle heterogeneity based on a shear-velocity model of Gu et al. (13) is plotted. Red colors indicate slower than average velocity, and blue colors indicate faster than average velocity. The cross section is made along a great circle between Africa and the southwestern Pacific (crossing under Eurasia). (B) Geometry of the DF ray in the inner core (pale- blue circle), where {xi} is the angle of the ray with respect to the symmetry axis (shown in red). At high values of cos2{xi}, the ray is traveling parallel to the symmetry axis, and when cos2{xi} is small, the ray is traveling perpendicular to the symmetry axis.
