Assessment of seismicity model for hong kong region

The seismicity model, the Gutenberg-Richter magnitude-frequency relationship. has been developed for Hong Kong region. Detailed investigation and statistical tests on the completeness of the earthquake catalogue and the regional variation of the seismicity have been carried out. It has been found that in the catalogue compiled in this study the historical records on land since 1895 are likely to be complete for surface-wave magnitude M = 4 % or greater. and that there is no record before 1920 in offshore area about 100 km from coastal lines. Almost all historical records before 1894 are on land. indicating that the historical records may be complete only on land. The earthquake spatial distribution is not uniform on land. The number of earthquakes with M = 6 or greater per year in the last 100 years is much larger than that in the previous historical time (1500–1894). It has also been found that the regional variation of the seismicity is a significant factor likely to affect the seismic hazard in Hong Kong. After detailed study. three source regions (S1, S2, and S3) are proposed. and a seismicity model is developed for each region. The difference Of seismicity between three regions is significant. Because of the relative high seismic activity in the last 100 years compared with the previous time. models based on the records of last 100 years are developed and they can be considered as the upper bounds for the seismicity Of Hong Kong region. Alternative models based on the records with M = 5.5 or greater since 1800 are also evaluated and they can be considered as appropriately conservative models. Although the models developed here predict a considerably higher level Of seismicity for large magnitudes than those published in literature for Hong Kong. the seismicity level Of the region affecting Hong Kong is still found to be low-moderate compared with many seismically active overseas countries. such as Japan, Western USA and New Zealand but is much higher than that in UK.