ASSESSMENT OF SCHEMES FOR EARTHQUAKE PREDICTION - EDITORS INTRODUCTION

This contribution introduces a series of papers on the assessment of s chemes for earthquake prediction, originally presented at an RAS/JAG D iscussion Meeting. The papers also address the social and administrati ve implications of earthquake prediction and the question whether this objective is feasible in either a strictly scientific or a socially u seful sense. Contributions on the assessment process itself stress the importance of clearly defining procedures and anticipated outcomes in advance of any prediction experiment. After-the-fact searches for cor relations drastically weaken the statistical significance of any assoc iation which is found. The record of a proposed prediction scheme can be made to appear more significant by comparing it with an inadequate or unsuitable model of seismicity. Because the distribution of earthqu akes is clustered in both time and space, simple models (e.g. Poisson distribution in time) do not fully characterize it, and statistical te sts which rely on such assumptions are inappropriate. The history of a ttempts to predict earthquakes suggests that little if any progress is being made towards the goal of specifying-in advance and within reaso nably tight limits-the time and place of occurrence and the size of th e forthcoming event. The view that prediction may be impossible is reg aining support following a change in perception regarding the nature a nd origin of earthquakes and faulting. Reid's elastic rebound model an d its associated conceptual framework of a near-homogeneous Earth are being superseded by a fundamentally heterogenous model employing the s tochastically oriented concept of self-organized criticality. Within t he latter model, both the initiation and the eventual progress of rupt ure on a fault depend on a multitude of factors related to both local stress and strength, which are inter-related and heterogeneous beyond practical measurement. Thus, the course of a fracture towards large-sc ale failure cannot practically be determined in advance. Other contrib utors show that an unusually high degree of scientific confidence is r equired in order for a prediction to be of significant social value. T herefore, in terms of saving both lives and property, statistical appr oaches to hazard assessment, combined with appropriate programmes of r isk reduction, continue to offer the most cost-effective means of redu cing earthquake-related losses.