OpenSHA implementation of the GCIM approach for ground motion selection
Ground motion selection is known to be an important step in seismic hazard and risk assessment. There have been numerous procedures proposed for selecting ground motions ranging from somewhat ad-hoc guidelines specified in seismic design codes to more rigorous approaches which have found favour in the research-community, but are not yet applied routinely in earthquake engineering practice. The most common method (often specified in seismic design codes) for selecting ground motion records for use in seismic response analysis is based on their "fit" to a Uniform Hazard Spectrum (UHS). This is despite the fact that many studies have highlighted the differences between the UHS and individual earthquake scenarios, and therefore its inappropriateness for use in ground motion selection. The reluctance of the earthquake engineering profession to depart from UHS-based selection of ground motions is arguably because of its simplicity to implement relative to methodologies with sounder theoretical bases. To this end, the aim of the present work was to implement a recently developed Generalised Conditional Intensity Measure (GCIM) approach for ground motion selection (Bradley, 2010) into the open-source seismic hazard analysis software OpenSHA (Field et al. 2003).