Abstract

At the high latitudes of the southern hemisphere, the seismicity maps are strongly biased as a consequence of the low density of seismic stations and the high permanent microseismic noise. In the frame of the Geoscope project, a network of four long-period and broadband stations has been set up in Antarctica, Crozet and Kerguelen Islands, and New Caledonia by the Institut de Physique du Globe de Strasbourg, the Terres Australes et Antarctiques Françaises, and the Office de la Recherche Scientifique et Technique d'Outre Mer. This network has revealed that about 200 earthquakes of magnitude 4.3 to 5.5 were ignored each year in the global seismicity for that part of the Earth. Using the propagation of Rayleigh waves and a simple velocity model, about 20 earthquakes have been located for 1986 in South Pacific Ocean, South Indian Ocean, and Antarctica, with an accuracy on the order of 100 km. These new events provide a refined image of the seismicity at the high southern latitudes. Most of them are located along the plate boundaries between the Antarctic, Australo-Indian, and Pacific plates. A few events located in Pacific Ocean east of Australia and on the Antarctic plate could possibly correspond to a small intraplate activity. These preliminary results show the potentiality of significantly improving the seismicity maps at the southernmost latitudes from Rayleigh-wave analysis if a greater number of broadband stations and regional velocity models are used.

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