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Proceedings of the International Conference on
Advances and New Challenges in Earthquake
Engineering Research, Hong Kong Volume
DRIFT-BASED SEISMIC ASSESSMENT OF BUILDINGS
IN HONG KONG
A.M. Chandler 1 , R.K.L. Su 1 and M.N. Sheikh 1
1 Department of Civil Engineering, The University of Hong Kong,
Pokfularn Road, Hong Kong SAR, China
ABSTRACT
Large magnitude earthquakes generated at distances exceeding 100km are typified by low frequency
(long period) seismic waves, since the high frequency components have greatly diminished in amplitude
as a result of energy absorption along the wave travel path. The peak ground acceleration (PGA), or
response spectral accelerations (RSA), from such distant earthquakes can be very low and yet the
induced motion can be highly destructive due to its high displacement (drift), and possibly high velocity,
shaking characteristics. This paper introduces a methodology for predicting the response spectral
displacement (RSD) using the Component Attenuation Model (CAM). Hence, the critical drift demands
from long distance earthquakes affecting tall buildings in Hong Kong have been estimated. It is shown
that soil (site) resonance effects play a critical role in determining the level of seismic drift demand.
1. INTRODUCTION
Large magnitude, distant earthquakes represent the critical design events for the prevalent medium-rise
and high-rise construction in Hong Kong (Lam et al, 2002). This paper firstly introduces attenuation
relationships to predict the velocity and displacement (drift) demands from long distance earthquakes,
based on stochastic simulations for the crustal conditions of South China. The Component Attenuation
Model (CAM) procedure, so developed, is based on separating the "source", "path" and "site" effects.
Such separation is intended to address the fact that attenuation of seismic waves is strongly dependent
on regional properties of the earth's crust, through which seismic waves are propagated and modified.
This regional crustal influence is particularly significant for seismic waves propagating over a long
distance (site-source distance R> 100km). Response spectrum formats that can effectively represent
such effects are shown in Fig's 1.1 a and Lib, and the parameters of interest are accordingly RSD max
and RSV rtulx . Existing empirical response spectrum attenuation relationships from high seismic regions
are typically based on strong motions recorded in the near-field. Thus, they cannot be relied upon to
model distant earthquakes. The recorded ground shaking on different sites, and in different regions, can
vary significantly even for very similar moment magnitude (M) and site-source distance, R (km). By