Frequency-magnitude relationships for seismic areas around the capital cities of Solomon, Vanuatu, Tonga and Fiji Islands

We studied the relationships between the frequency of occurrence and the ma gnitudes in seismogenic areas that will affect four capital cities in the S outh Pacific, namely: Honiara in Solomon Islands, Port Vila in Vanuatu, Suv a in Fiji and Nuku'alofa in Tonga. We used the NEIS catalogues for the peri od 1973-1997, for magnitudes greater than about 5, in the proximity to the city under investigation. The definitions of the geographic boundaries of t he seismogenic zones are based on the classical concepts of the distributio n of the tectonic plates, the overwhelming number of studies that describe the seismotectonics in those active regions and on the observed seismicity and studies of the local people. Completeness of the catalogue is assumed b ecause of the high seismicity in these areas, despite the relatively short time span. We have used a hybrid process combining least squares fitting an d Newtonian search process to find the best fit of the statistical paramete rs. The characteristic b value is 1.27, and seems to be irrespective of the depth and/or region.