Seismic Hazard Evaluation for Sites in California: Development of an Expert System

Seismic hazard analysis is now 25 years old. The number of models that have been developed to describe earthquake recurrence, magnitude distribution, and ground motion attenuation has reached a value greater than twice this age. The engineer evaluating the seismic hazard at a site is faced with the problems of understanding these numerous models, gathering and manipulating the appropriate data for parameter estimation, and interpreting the results. Only a few senior engineers and experienced researchers are able to analyze the seismic hazard in a consistent way. To assist engineers new to this field in selecting the appropriate models and in interpreting the results, a self-documenting tool needs to be developed. Seismic hazard experts can express their judgment in the form of heuristic rules based on their broad knowledge and experience. An expert system approach can be adopted to recreate this expertise since this approach possesses the necessary characteristics to capture this type of knowledge representation and access the required database.

The system is built using the IBM based expert system shell, INSIGHT2+1 to control the problem solving strategy and the C programming language for computational algorithms. The system is developed to provide a general framework that can accommodate any recurrence or attenuation model for evaluating the seismic hazard of sites in California. If a model is not already included in the system, it can be easily incorporated by specifying its formulation. The uncertainty associated with the models and data used for seismic hazard analysis is carried through to the final results using the bootstrap statistical method. The system is designed to use incomplete seismic records optimally in the assessment of seismic hazard and is general enough to be implemented for other seismic regions by simply providing the earthquake, seismic source, and geology data for these regions.