Deterministic seismic hazard parameters and engineering risk implications for the Hong Kong region

Abstract

The paper reviews and compares recent regional studies evaluating the seismic hazard parameters required to assess the seismic risk to engineering construction in the Coastal Region of South China (CRSC) including Hong Kong (HK). The review establishes that the CRSC, and in particular the offshore seismic belt, has mean earthquake magnitude recurrence intervals (MRIs) or return periods that are 2–3 times shorter than those in the eastern United States (EUS), with which the HK region has been compared. An ensemble of realistic design-level earthquake events suitable for defining the regional seismic hazard and for undertaking engineering risk assessment is then formulated, in the form of deterministic magnitude–distance pairs associated with earthquake magnitudes having a range of MRIs, and the significance of the maximum credible earthquake (MCE) magnitude is highlighted. Next, the scenario earthquake events have been used to predict the expected levels of peak design ground motions (for bedrock) in the HK region. The approximate method proposed here indicates that peak (effective) ground accelerations may reasonably be estimated to be around 10% g for 500-year earthquake events and 15–20% g for 1000-year events. However, the predicted ground motions arising from design-level earthquake events indicate large uncertainties arising from the attenuation equations. The uncertainties arise from both epistemic (event-to-event) and aleatory (site-to-site) considerations. These uncertainties represent the greatest source of errors in defining the seismic hazard for engineering design purposes. Further research is required to define the attenuation characteristics of ground motions for the CRSC, across a range of parameters including ground displacement and velocity as well as acceleration. It is further found that the Chinese earthquake building code gives a reasonably conservative estimate of seismic demand for the region, and is quite consistent with results from both probabilistic and pseudo-probabilistic seismic hazard analysis carried out herein, and by other researchers over the past 7 years. Finally, a discussion is presented of some key issues related to earthquake-resistant design and performance in Hong Kong, including the necessity to consider a range of design-level events with different MRIs when implementing acceptable structural design for earthquake effects.