Evaluation of site-specific seismic design requirements for three Canadian cities

Siesmic design requirements as specified in building codes normally use a generic approach in which the seismic response is independent of the site location, except for a single intensity-related parameter used to define the severity of the expected ground motion. In reality, the characteristics of earthquakes that influence structural response depend on both the level of seismic motion and the seismo-tectonic environment at the specific location. This paper describes a methodology for determining seismic design requirements that uses both magnitude (M) and epicentral distance (R) to define the seismo-tectonic environment. Ensembles of actual seismic strong motion records are selected to match the combinations of M and R that dominate the seismic risk at a specific location. These time histories are used to determine both response spectra and seismic response factors (as used in the 1985 edition of the National Building Code, NBCC 1985) for the location in question. This paper applies this methodology to Vancouver, Ottawa, and Quebec City and compares the results with the response spectra and seismic response factors specified in NBCC 1985. The results indicate that a site-specific investigation of seismic design requirements is important in distinguishing between locations having different seismo-tectonic environments. Key words: structures, design, seismic, code, dynamic, acceleration, velocity, spectra, magnitude, epicentral distance.