Publications des scientifiques de l'IRD

Recq M., Charvis Philippe. (1986). A seismic refraction survey in the Kerguelen isles, southern Indian Ocean. Geophysical Journal of the Royal Astronomical Society, 84, p. 529-559.

Titre du document
A seismic refraction survey in the Kerguelen isles, southern Indian Ocean
Année de publication
1986
Type de document
Article
Auteurs
Recq M., Charvis Philippe
Source
Geophysical Journal of the Royal Astronomical Society, 1986, 84, p. 529-559
Two 65 km long on land refraction lines, with shot detonated at sea, were implemented in the Courbet Peninsula, eastern region of the Kerguelen archipelago (Terres Australes et Antarctiques Françaises, southern Indian Ocean). The first profile P1, oriented NE SW, runs from Cap Ratmanoff toward Mont Ross, and the second one, P2, from Pointe Suzanne, SE of the Courbet Peninsula, through the Val Studer. Data from both profiles were supplemented by using the Bouguer gravity anomaly map not previously studied. The data combined standard travel time interpretation, wide angle reflected wave study, synthetic seismograms and S wave analysis. The velocity depth behaviour shows that the mean crustal thickness ranges from 14 to 17 km only, varying with the locality. The structure of the crust beneath Kerguelen resembles those observed beneath aseismic ridges (i.e. the Crozet Rise and the Madagascar Ridge). Average velocity of 5.5 km s 1 on both lines is in the range of those determined for oceanic layer 2, which is there 8 9 km thick. Average velocity of 6.6 km s 1 is in the range of velocities within oceanic layer 3. The transition to mantle velocity, 7.95 km s 1 is best modelled by a positive velocity gradient within the crust. This feature is similar to that observed on structures generated near spreading centres. These new data combined with geological and geochemical investigations in the archipelago support an oceanic origin for the Kerguelen Heard Ridge, and also Broken Ridge. Both structures were joined 40 Myr ago, as shown by the magnetic anomaly pattern. Refraction studies invalidate the assumption that isostatic compensation is achieved by a 23 km deep crustal root, but substantiate the contribution of a low velocity mantle. Gravity data are consistent with refraction studies. No crustal root appears to be present beneath Mont Ross. The best match between gravity and refraction data in the Val Studer is obtained by assuming the presence of a shallow intrusive body, related to the fault and dyke system, and Montagnes Vertes plutonic intrusive complex nearby.
Plan de classement
Sismologie [066SISMO]
Descripteurs
GEOPHYSIQUE ; SISMOLOGIE ; SISMIQUE A REFRACTION ; ONDE SISMIQUE ; PROPAGATION D'ONDE ; GRAVIMETRIE ; CARTOGRAPHIE
Description Géographique
OCEAN INDIEN ; KERGUELEN
Localisation
Fonds IRD [F B43445] ; Nouméa
Identifiant IRD
fdi:43445
Contact