WLIFT MOVEMENTS IN NEW CALEDONIA-LOYALTY ISLANDS AREA AND THEIR PLATE TECTONICS INTERPRETATION

ABSTRACT Dubois, J., Launay, J. and Recy, J., 1974. Uplift movements in New Caledonia-Loyalty Islands area and their plate tectonics interpretation. Tectonophysics, 24: 133-150. The uplift movements of the New Caledonia and the Loyalty Islands, which are located on the Indian lithospheric plate that descends beneath the New Hebrides arc, have been studied in the geological context. This paper concentrates on the older (since Oligocene) uplift of the ultramafic peneplain in New Caledonia and the younger (since about 2 m.y.) regional uplift of the Loyalty Islands and southern New Caledonia. We computed the amount of uplift and deformation caused by three possible processes: erosional unloading, eustatism, and flexure of the lithosphere as it underthrusts beneath the New Hebrides island arc. The calculations indicate that the older uplift cannot be completely explained by erosional unloading of New Caledonia and may be partially caused by dynamic factors not yet understood. Eustatic uplift of New Caledonia in compensation for the rise in sealevel is also of insufficient amplitude to explain the uplift observed since about the last 2 m.y. Studies of the flexure of the lithosphere caused by subduction beneath the New Hebrides arc provide an explanation for the observed recent uplift of the emergent atolls of the Loyalty Islands

Development patterns of fringing and barrier reefs in New Caledonia (southwest Pacific)

International audienc

Vanuatu fossil coral SST reconstruction for 4200 yr BP

We present a 47-year-long record of sea surface temperature (SST) derived from Sr/Ca and U/Ca analysis of a massive Porites coral which grew at ~4150 calendar years before present (B.P.) in Vanuatu (southwest tropical Pacific Ocean). Mean SST is similar in both the modern instrumental record and paleorecord, and both exhibit El Niño-Southern Oscillation (ENSO) frequency SST oscillations. However, several strong decadal-frequency cooling events and a marked modulation of the seasonal SST cycle, with power at both ENSO and decadal frequencies, are observed in the paleorecord, which are unprecedented in the modern record

Interseismic and coseismic motions in GPS series related to the Ms 7.3. July 13, 1994, Malekula earthquake, central New Hebrides subduction zone

On July 13, 1994, an earthquake Ms = 7.3 occurred at Malekula, in the New Hebrides archipelago. The GPS data collected across the New Hebrides trench between 1990 and 1996 were processed in order to separate the interseismic and coseismic motions from the drifts related to the convergence with the Australian plate. The GPS-derived coseismic displacements at the GPS site in Malekula are 49 = 15 mm southward, 230 = 30 mm westward and 170 = 37 mm downward, when the CMT-derived displacements are 50 mm southward, 210 mm westward and 150 mm downward. Taking into account the interseismic strain accumulation (25 mm/yr at the source established from historical seismicity, 7.5 mm/yr at the GPS site), the strain-free convergence rate at Malekula is 49 = 3 mm/yr. Other GPS-derived convergence rates are 95 = 1 mm/yr at Efate and 37 = 2 mm/yr at Santo. These rates imply a regional right-lateral motion between the Efate and the Santo-Malekula segments. In contrast, the focal mechanism of the earthquake mostly indicates a lift-lateral motion. Therefore, we hypothesize that the earthquake is related to variations in the interplate coupling along the converging boundary of the Santo-Malekula segment. (Résumé d'auteur

Interseismic and coseismic motions in GPS series related to the Ms 7.3. July 13, 1994, Malekula earthquake, central New Hebrides subduction zone

On July 13, 1994, an earthquake Ms = 7.3 occurred at Malekula, in the New Hebrides archipelago. The GPS data collected across the New Hebrides trench between 1990 and 1996 were processed in order to separate the interseismic and coseismic motions from the drifts related to the convergence with the Australian plate. The GPS-derived coseismic displacements at the GPS site in Malekula are 49 = 15 mm southward, 230 = 30 mm westward and 170 = 37 mm downward, when the CMT-derived displacements are 50 mm southward, 210 mm westward and 150 mm downward. Taking into account the interseismic strain accumulation (25 mm/yr at the source established from historical seismicity, 7.5 mm/yr at the GPS site), the strain-free convergence rate at Malekula is 49 = 3 mm/yr. Other GPS-derived convergence rates are 95 = 1 mm/yr at Efate and 37 = 2 mm/yr at Santo. These rates imply a regional right-lateral motion between the Efate and the Santo-Malekula segments. In contrast, the focal mechanism of the earthquake mostly indicates a lift-lateral motion. Therefore, we hypothesize that the earthquake is related to variations in the interplate coupling along the converging boundary of the Santo-Malekula segment. (Résumé d'auteur