Investigations into earth's crustal structure from the observations of seismic surface waves since 1955 were reviewed. In this first paper, the results of estimation concerning the oceanic crustal structure are given. 1. Pacific Ocean : Dispersions of Rayleigh waves due to both natural shocks and nuclear explosions have been observed along as many as more than 300 different paths. Rather continental crustal structure in the western side of Andesite line is quite clear from the dispersion of Rayleigh waves. Interesting fact is the abnormal dispersion character of Rayleigh waves along the paths through the East Pacific Rise. General crustal view in the whole Pacific basin has been given. 2. Atlantic Ocean : Noticeable fact is that dispersion of Rayleigh waves along the Mid-Atlantic Ridge has the same character as that along the East Pacific Rise. 3. Arctic Ocean : It has been revealed from the observation of both Lg waves and dispersion of Rayleigh waves that area of oceanic basin is rather small. 4. Indian Ocean : Investigations of crustal structure in this Ocean is still scanty. 5. From the observation of Lg waves, Bearing Sea and central Part of Japan Sea have both been concluded to have oceanic crusts. Most part of Okhotsk Sea, however, looks like to have continental crustal structure. 6. Many observational results have revealed the continental crustal structures in East China Sea and Yellow Sea basins. 7. The thickness of the sedimentary layer has been estimated at some Bays.
Survey of old records concerning the publication on mercury provides a very useful means to trace exhausted and forgotten mercury mines and thus complete the gaps in the distribution of mercury are deposits in the Japanese segments of the Circum-Pacific metallogenetic zone. The discovery of a mercury mineral in 198 A. D. is described in “Shoku Nihonki”, the earliest literature referring to the Japanese mercury. The mining of the metal in record, however, dates as far back as the Asuka period (600 A. D.) and a peak production was once reached during the Heian period. In those early days, mercury was used principally for medicine, amalgam base for gold-gilding on Buddha statues, and ship paint. The mining was operated throughout Japan by the “Niu” tribe, an ethnic group which was once headed by “Niuzuhime” in Yoshino region and later spread out searching for new deposits. “Niu” means cinnabar and also red color in Chinese. For this reason, villages in former mercury-producing district often bear the name of Niu and have shrines called “Niu Jinja” which are dedicated to Niuzuhime. It is also reported in literature that the search for mercury was also conducted by “Yamabushi”, a group of itinerant buddhist priest who travelled around the country carrying the will of Kobo-daishi, the famous founder of their sect. Although the occurrence of mercury in “Hitachi” and “Dewa” districts was mentioned in ancient literature, no mercury deposits have been discovered geologically in recent years. The mercury contents of reddish clays from these localities, however, are high enough to be indicative of the presence of such are deposits.