HOW WELL DO WE UTILIZE GLOBAL SEISMICITY

This article describes a method for quantifying the ability to record teleseismic phases at particular epicentral distance ranges, given the geographical history of global seismicity. With the use of geographic al sampling maps, we identify the regions of the Earth that are best s uited to record the greatest numbers of earthquakes at particular dist ances. Since seismic studies of the Earth's interior use teleseismic p hases that have unique ranges, this information can be useful in the p lanning of future permanent and temporary deployments of seismometers. Deployment of ocean-bottom seismometers would be required for recordi ng large numbers of earthquakes in the 40 degrees to 80 degrees range, corresponding to phases like ScS and PcP, and in the 140 degrees to 1 70 degrees range, important for investigations of the PKP branches. An examination of existing analog and digital networks shows that they d o either better or worse than a hypothetical grid of evenly spaced sei smometers, depending upon the distance range examined. The use of temp orary deployments of seismometers, perhaps even in the oceans, may be the best way to significantly sample poorly examined regions of the Ea rth's interior.