Identification of fault zones using gravity survey and subsurface exploration : a case study
The proposed Landmark Tower of the Kowloon Station is located within the West Kowloon reclamation adjacent to the Mass Transit Railway Kowloon Station and its southern approach tunnel.
Preliminary drillhole investigations at Kowloon Station implied the presence of a linear northwest-southeast depression in rockhead, which appeared to persist across the northern half of the site. The linear zone of depressed rockhead may be attributed to a weathered geological fault or fractured zone. A gravity survey was designed to define the location, extent and form of the rockhead depression as guidance for a subsequent planning of additional drillholes.
The main purpose of this dissertation project is to correlate the results obtained from the existing borehole investigations and gravity survey to identify the nature and alignment of fault zones thought to be passing through the site. A prediction of whether these faults are active will be carried out by drawing on published information on the history of the fault movement/seismic activities in the Hong Kong region.
The gravity data acquisition was carried out by EGS (Asia) Limited in January 2001 and Cosine Limited was appointed as the geophysical consultant. The ground investigation works were carried out by Lam Geotechnics Limited.
From the study, the following conclusions can be made.
? The gravity survey results were found to be particularly useful for the identification of possible fault zones in this site and variations in rockhead profiles.
? It was found that the gravity model generally correlated well with the borehole data. This may be due to the thickness of the unconsolidated cover being well defined in the preliminary drilling works; the survey was conducted in an area of minimal traffic and residential noise and the variations in densities of the soil were obtained from site specific laboratory testing results.
? Dominate northwest - southeast and northeast - southwest trending lineations from the residual anomaly plot correlate well with the observed northwest -southeast trending fault zones offset by a northeast - southwest fault structure determined from the drillhole records.
? A comparison of the gravity and rockhead contour plots showed that an area of low anomaly near the centre of the site corresponding to depressed rockhead.
? Based on the published thermoluminence dating results of material obtained from the northwest trending faults in Hong Kong, it is suggested that this fault zone is likely to be active.
School:The University of Hong Kong
School Location:China - Hong Kong SAR
Source Type:Master's Thesis
Keywords:faults geology china hong kong gravity boring
Date of Publication:01/01/2004