MAGNETIC ANOMALY PATTERNS AROUND THE CENTRAL RIFT AREA IN THE NORTH FIJI BASIN - INVERSION APPROACH FOR DETAILED STRUCTURE

A detailed magnetic anomaly map around the central rift area in the No rth Fiji Basin was compiled from 6 STARMER cruises. The data range is almost 800 km in length (between 22-degrees-S and 14-degrees-30'S), 10 0 km in width (between 173-degrees-E and 175-degrees-E). Detailed magn etic structure analysis was applied for the data around the rift axis, which revealed 5 or 6 segments along the 800 km long rift axis. Inver sion trials were done on the grid data and good comparison with topogr aphic features was obtained. The results of inversion indicate that th e lineations which correspond to the Olduvai event were recognized in this area broadly, but not so common as those for the Gauss epoch. The central rift system seems to have started its spreading from around t he end of the Gauss normal epoch or the beginning of the Matuyama reve rsed epoch (2.5 Ma).