Cavascope: The Broadband Seismological Network of the New Hebrides Subduction Zone and Its Associated Data Base

Abstract

Beginning in 1993, a seismological broadband network (named the Cavascope network) was set up in New Caledonia and Vanuatu in the Southwest Pacific, within a collaborative framework of researchers from the Institut de Recherche pour le Developpement, Noumea, New Caledonia (IRD); Ecole et Observatoire des Sciences de la Terre, Strasbourg, France (EOST); and the Department of Geology, Mines and Water Resources of Vanuatu (DGMWR). This seismological network, located in a particularly fast converging area, i.e. , the New Hebrides subduction zone, and surrounded by numerous other very active seismic zones (Papua New Guinea, Salomon Islands, Fiji, Tonga-Kermadec, and New Zealand) is of great interest to the scientific community. In this article, we give a short overview of the tectonic setting of the region and past seismological surveys, and then we present the instrumental characteristics of the Cavascope network and its associated database. The active margin of New Hebrides is associated with the subduction of the Australian plate under the North Fiji Basin. This extends 1,500 km from the Santa Cruz archipelago in the north up to 23 degrees south, including the entire Vanuatu archipelago (figure 1). This seismic zone is dipping with an angle of 60–70° down to a depth of 300 km. The plate convergence axis trends ENE, perpendicular to the trench, and the convergence rate reaches 12 cm/year in the south and 16 cm/year in the north, with a minimum of 4 cm/year observed near the central part of the margin (Pelletier et al. 1998; Calmant et al. 2003). These high convergence rates produce a high level of seismicity that each year yields more than 10 earthquakes of moment magnitude (Mw) higher or equal to 6.0. Despite the area's high seismic potential and volcanic hazards (Louat and Baldassari 1989; Eissen et al. 1991; Robin and …