Tectonic plate motion and co-seismic steps surveyed by DORIS field beacons:: the New Hebrides experiment

The New Hebrides experiment consisted of setting up a pair of DORIS beacons in remote tropical islands in the southwestern Pacific, between 1993 and 1997. Because of orbitography requirements on TOPEX/Poseidon, the beacons were only transmitting to SPOT satellites. Root-mean-square (RMS) scatters at the centimeter level on the latitude and vertical components were achieved, but 2-cm RMS scatters affected the longitude component. Nevertheless, results of relative velocity (123 mm/year N250 degrees) are very consistent with those obtained using the global positioning system (GPS) (126mm/yr N246 degrees). The co-seismic step (12 mm N60 degrees) related to the Walpole event (M-W = 7.7) is consistent with that derived from GPS (10 mm N30 degrees) or from the centroid moment tensor (CMT) of the quake (12 mm N000 degrees).