SEISMICITY IN SUBDUCTION ZONES FROM LOCAL AND REGIONAL NETWORK OBSERVATIONS

The data provided by local and regional seismograph networks are essen tial for the solution of many problems of subduction-zone seismology. The capabilities of such networks are limited by the instrumentation c urrently in common use and the unfavorable source-station geometry oft en imposed by the regional geography. Nevertheless, important contribu tions have come from the data gathered in many of the earth's subducti on zones. The accuracy of hypocenter locations based on regional data is affected by the complex velocity structures characteristic of subdu ction zones, but the problems are now well-understood. Examples of num erous studies of the spatial configurations of the seismicity in subdu ction zones and consequent interpretations of seismogenesis and subduc tion processes are reviewed. Studies of the distributions of earthquak es in time and with magnitude, for events down to the microearthquake level, have the potential for clarifying the earthquake-generating pro cesses and, possibly, a basis for earthquake prediction. Other uses of local and regional network data have been for investigations of coda- Q and the identification of asperities in subduction zones.