Seismological constraints on ice properties at Dome C, Antarctica, from H/V measurements.

Jean-Jacques Lévêque (1) , Alessia Maggi (1) , Annie Souriau (2)

1 IPGS-Sismologie - Sismologie (IPGS)
2 IRAP - Institut de recherche en astrophysique et planétologie

The French-Italian Concordia (CCD) seismological station at Dome C is one of two observatories setup on the ice cap in the interior of the Antarctic continent. We analysed the seismic signal due to ambient noise at this station and at three temporary stations 5 km away from Concordia, in order to specify the ice properties beneath them. A method based on the horizontal to vertical (H/V) spectral ratio, commonly used to analyse soil response in seismic regions, was applied to the Antarctic stations. The main peak in the spectral ratios is observed at frequencies 6.7-8 Hz at the Dome C stations, but it is not observed at another station on the ice cap, QSPA, where the sensor is buried at 275m depth. This peak can be explained by a 23m thick unconsolidated snow or firn layer with a low S-wave velocity of 0.7kms-1, overlying a consolidated layer with S-wave velocity 1.8 km s-1. Despite the non-uniqueness of the solutions obtained by fitting the H/V spectra, this model is preferred because the depth of the velocity contrast coincides with the density at which ice particles arrange themselves in a continuous, dense lattice. A small variability of this structure is observed around Dome C.

Mots clés: Antarctic seismological stations; Concordia; firn; seismic ambient noise

Domaines: Géophysique [physics.geo-ph]; Géophysique [physics.geo-ph]; Milieux et Changements globaux

Jean-Jacques Lévêque, Alessia Maggi, Annie Souriau. Seismological constraints on ice properties at Dome C, Antarctica, from H/V measurements.. Antarctic Science, 2010, 22 (5), pp.1-8. ⟨10.1017/S0954102010000325⟩. ⟨hal-00679373⟩