抄録
In spite of a widely accepted trend of settling large-scaled artificial reef groups, the structure of the actually
settled ones is scarcely verified, because the suitable equipment was hardly available until recent.
A survey by using highly sophisticated electronic devices was conducted in October 1991, off Nagato for the
13 groups of artificial reefs settled. And the following results were obtained :
The side scan sonar (500kHz, 150m range each side) was proved to be very effective for the present
purpose, as supported by the fact that as many as 95% of the component reefs could be detected by sailing at
3.5 knots along parallel courses of 200m intervals.
Most of the component reefs in the circle type groups were found within the planned range, while the
aberration of their settled positions in the pseudo-ellipse type reef groups was mainly due to that of center blocks
settled by hanging methods basing on the indication from Loran C.
