INITIATION PROCESS OF EARTHQUAKES AND ITS IMPLICATIONS FOR SEISMIC HAZARD REDUCTION STRATEGY

For the average citizen and the public, ''earthquake prediction'' mean s ''short-term prediction,'' a prediction of a specific earthquake on a relatively short time scale. Such prediction must specify the time, place, and magnitude of the earthquake in question with sufficiently h igh reliability. For this type of prediction, one must rely on some sh ort-term precursors. Examinations of strain changes just before large earthquakes suggest that consistent detection of such precursory strai n changes cannot be expected. Other precursory phenomena such as fores hocks and nonseismological anomalies do not occur consistently either. Thus, reliable short-term prediction would be very difficult. Althoug h short-term predictions with large uncertainties could be useful for some areas if their social and economic environments can tolerate fals e alarms, such predictions would be impractical for most modern indust rialized cities. A strategy for effective seismic hazard reduction is to take full advantage of the recent technical advancements in seismol ogy, computers, and communication. In highly industrialized communitie s, rapid earthquake information is critically important for emergency services agencies, utilities, communications, financial companies, and media to make quick reports and damage estimates and to determine whe re emergency response is most needed. Long-term forecast, or prognosis , of earthquakes is important for development of realistic building co des, retrofitting existing structures, and land-use planning, but the distinction between short-term and long-term predictions needs to be c learly communicated to the public to avoid misunderstanding.