Earthquake Engineering Research - HKU Libraries - The University ...

20
jointly organized an International Workshop on Earthquake Engineering for Regions of Moderate
Seismicity. No doubt, earthquake resistant design for structures in Hong Kong is now an important
issue that needs urgent attention. In the early 2002, the Buildings Department of the Hong Kong SAR
government has issued a consultancy project CAO K49 on "Seismic Effects on Buildings in Hong
Kong" worth about 5 millions HKS. More earthquake-related studies for Hong Kong are expected in
the future.
In terms of the seismic design code of China (GBJ11-89), Hong Kong is classified as an area of
Seismic Intensity VII. And according to the newest Chinese seismic code (GB 18306-2001) the peak
ground acceleration is expected to be 0.15g in a return period of 475 years. It seems that, Hong Kong
should be regarded as an area with moderate seismic risk. According to the China Seismological
Bureau, buildings to be constructed in any region with an intensity level of VI or above in 475 years
should be designed in compliance with the seismic provisions of the Chinese code. Thus, it is expected
that seismic provisions will eventually be required for designing buildings in Hong Kong in order to
withstand seismic hazards. Inherited strength of existing structures will have to be assessed and
strengthened to safeguard our building stock and infrastructures against possible seismic attack. We
should emphasize that the hazard intensity level at Haicheng, Tangshan, and Yingtai before the
Haicheng earthquake, Tangshan earthquake and Yingtai Earthquake is only estimated at intensity VI,
which is lower than the current hazard in Hong Kong. Therefore, the conception that Hong Kong is
safe from large earthquake is a very misleading concept.
DANGAN ISLAND—POTENTIAL SEISMIC SOURCE FOR HONG KONG
As mentioned earlier, on June 23, 1874 an earthquake of magnitude 5.75 occurred at Dangan Island,
which is about 35 km southeast of Hong Kong Observatory. The earthquake led to an earthquake
intensity of V-VI in Hong Kong. The isoseismal trended along the ENE-WSW direction as shown in
Fig. 5.
Figure 5. The isoseismal of the 1874 Dangan Island earthquake together with those of the Heyuan
earthquake