Evaluating site effects for estimation of seismic ground response: a practical approach

Abstract

Expansion of scientific methodologies to estimate the probable extents of ground motion effects in earthquake-prone areas is crucial for proper planning, investigation, and design of engineering structures. In this regard, accurate estimation of site effects instigated by the terminal geological structure at a considered location, in the presence of a seismic tremor, plays a particularly significant role. The key emphasis of this document is to develop a practical ground response analysis procedure comprised of a line of objective, well-outlined and simple-but-adept individual processes to address this aspect of the problem. In this study, to achieve that goal, a total of 1188 ground response analyses were performed for a combination of ground motion selection/scaling and equivalent-linear site response analysis techniques – all of which by itself constitute the current agreed practice within their parts – at 10 accelerometer sites. Each location evaluated herein was selected so that the recording station is a part of the Turkish Strong Ground Motion Network, with readily accessible, detailed geotechnical and geophysical reports; and at least a single earthquake event record, that correspond to the 10 per cent exceedance level in 50 years, existing. This allowed for a direct comparison of the result patterns obtained using each analysis component with the actual earthquake response; thus a truthful appraisal of how changing different parts of the overall procedure is reflected in the attained approximation level. For each station, the main output of the proposed method is a uniform hazard spectrum (UHS), fashioned in a similar way as that in major seismic codes. Therefore, as an auxiliary outcome of this assessment, a case study presenting the insufficiency of the currently adopted site factors for faithful estimation of site effects, and a vital application regarding how the suggested approach may play a role in improving the existing seismic code practice is as well provided.