AN OVERVIEW OF DEVELOPMENTS IN SEISMIC HAZARD ANALYSIS

Developments in seismic hazard analysis over the last few decades are overviewed, and a perspective is presented on current issues and new developments. Over the last 30 years, methods and data have been refined, but our overall understanding of seismic hazards in most regions, as applied to typical building codes, has not changed very much. Our seismic hazard zoning maps are a relatively simple and transparent consequence of the patterns of historical seismicity. Over time, we have refined our understanding of where and why earthquakes occur, and improved our characterization of the resulting ground motions and their probabilities. We have begun to understand the important role of uncertainty in seismic hazard analysis. However, there are still significant shortcomings in our treatment of uncertainty. The same lack of knowledge that causes our uncertainty of the hazard also prevents us from accurately quantifying that uncertainty. At present, new ground-motion data, available in near-real time, are allowing better insight into earthquake ground motion generation and propagation, and are laying the groundwork for real-time seismic hazard information systems that will be developed in the future. HISTORICAL OVERVIEW OF HAZARD ANALYSIS Seismic hazard analysis has been an element of good engineering design practice in modern countries for many decades; it is an integral component of building codes and standards for design of critical structure