Abstract: The thesis summaries China’s recent situations of geophysical prospecting in coral island and reef. Combined with the In-situ borehole test, three regular geophysical methods are adopted in the investigation of a coral island; their applicabilities and results are specified. It is shown that the active surface wave(ASW) and marine seismic reflection(MSR) can achieve satisfactory results; but the resistivity method is not suitable for coral island and reef. Apparent velocity profiling of ASW method figures out the geological stratigraphic sequence of coral clastic deposit and underlying reef limestone. MSR does well in the distinguishing the deposit interface of outer reef flat, seaward slope, offshore and discovers the unsymmetrical structure of sea bottom, deposit between the northeast and southwest survey line, which is probably related with the marine hydrodynamics in the coral growth and development. In-situ borehole test showes that the loose coral clastic sediments has little difference in electric resistivity with the reef limestone; therefore the resistivity method is overall not suitable for the geotechnical profiling for the reason of the same order of magnitude in electrical resistivity.

Key words: coral island and reef, engineering geophysical prospecting, high-density resistivity method, active surface wave, marine seismic reflection, in-situ borehole test