Geophysical studies of sediments in waters near Hong Kong and in the Gulf of St. Lawrence

by Wong, How-Kin

lUl acoustic survey has been carried out in three seleoted areas in the inshore waters of Hong Kong, two shallow areas beyon& the continental shelf in the South China Sea, and four others in the Southern Gulf of St. Lnwrence. The results are interpreted in

terms of the superfioial sediments and sedimentary oonditions of

the respeotive areas. Whenever possible, relationships vdth the neighbouring lund geology are also discussed.

Data obtained from measurements of backscattering of sound from the ocean bottom at 12 locutions in tho inshore waters of Hong Kong shay" th.:1,t the bottom backsCD:l;toring strength inc.reo.ses?roughly in the order ot ail ty cl[1,Y, olayey ail t, sundy ail t ,si.1Jldsilt-cl~y, silty stmd, sand tmd rock. For tho rDngo of grazing L~glos from 0.4 to 8 degrees, the backsco.ttering strength is ~~lmost Q. oonsto.nt. It is ooncluded that L'. knowledge of the percentago

of sand end the effective bottom roughness is particularly useful for the estimation of bottom reverberation levels.

Merits and limitations of the aoo~stic survey mothod are discussed, ~~d possible improvements of t~ equipment suggostod.

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