地学雑誌 Journal of Geography 102(7) 868-877 1993 日本列 島の 自然放射線 レベル 古 川 雅 英* Natural Radiation Level in Japan Islands Masahide FURUKAWA* Abstract Extensive field survey on natural radiation was conducted from 1967 to 1地学雑誌 Journal of Geography 102(7) 868-877 1993 日本列 島の 自然放射線 レベル 古 川 雅 英* Natural Radiation Level in Japan Islands Masahide FURUKAWA* Abstract Extensive field survey on natural radiation was conducted from 1967 to 1991 over Japan Islands. The average level of the islands was found to be 79.7 nGy/h. In general, South- west Japan has higher level compared with the Northeast one. From the data obtaine
