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

The paper reviews and compares recent regional studies evaluating the seism ic hazard parameters required to assess the seismic risk to engineering con struction in the Coastal Region of South China (CRSC) including Hong Kong ( HK), The review establishes that the CRSC, and in particular the offshore s eismic belt. has mean earthquake magnitude recurrence intervals (MRIs) or r eturn periods that are 2-3 times shorter than those in the eastern United S tates (EUS), with which the HK region has been compared. An ensemble of rea listic design-level earthquake events suitable for defining the regional se ismic hazard and for undertaking engineering risk assessment is then formul ated, 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 scena rio earthquake events have been used to predict the expected levels of peak design ground motions (for bedrock) in the HK region. The approximate meth od proposed here indicates that peak (effective) around accelerations may r easonably be estimated to be around 10% g for 500-year earthquake events an d 15-20% g for 1000-year events. However, the predicted ground motions aris ing from design-level earthquake events indicate large uncertainties arisin g from the attenuation equations. The uncertainties arise from both epistem ic (event-to-event) and aleatory (site-to-site) considerations. These uncer tainties represent the greatest source of errors in defining the seismic ha zard for engineering design purposes. Further research is required to defin e the attenuation characteristics of ground motions for the CRSC. across a range of parameters including ground displacement and velocity as well as a cceleration. 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-pro babilistic seismic hazard analysis carried out herein, and by other researc hers 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 di fferent MRIs when implementing acceptable structural design for earthquake effects. (C) 2001 Elsevier Science Ltd. All rights reserved.