A Basis for Evaluation of Seismic Hazard and Design Criteria for Saudi Arabia

This paper presents the fundamental issues and policy decisions that formed the basis of the hazard and design aspects of a comprehensive research project conducted for development of the preliminary seismic design criteria for the Kingdom of Saudi Arabia. The study represents the first regionally consistent and systematic collection and critical treatment of the limited historical and instrumental data on earthquakes and seismotectonics of the region, and development of seismic design criteria. The development of the seismic design criteria followed somewhat conservative course, rather than a strict scientific approach, in estimation of the seismic hazard. One of the significant outcome of the study was the preparation of an upto-date and refined earthquake catalog of the region. The catalog contains both, the historical data available in Arabian and English literature, and the data recorded by international and local seismic monitoring agencies. The data were critically treated and superimposed upon the available tectonic information of the Arabian peninsula to obtain a preliminary seismotectonic map of the region. The results of the probabilistic seismic hazard assessment indicate that the highest relative predicted ground-motion occurs near the northwestern border neighboring the Gulf of Aqaba and also near the southwestern border, neighboring Yemen. Based on iso-acceleration map for 10% probability of being exceeded in 50 years, for the seismic design purposes the Kingdom was delineated into four seismic zones. Following UBC format the seismic zones are assigned numbers 0, 1, 2A and 2B. Widely used codes, SEAOC and UBC were selected as the model for development of seismic design recommendations. Selection of the structural system is based on structural performance category which is determined by seismic zone number and the intended occupancy category. R _w -factors for different types of structural system were assigned lower values in consonance with the design and construction practices prevalent in the country. The significance of this study is in its implementation of a global scheme in development of seismic design criteria of a region beset with limited seismic data.