BULLETIN OF THE GEOLOGICAL SURVEY OF JAPAN
Online ISSN : 2186-490X
Print ISSN : 1346-4272
ISSN-L : 1346-4272
Volume 65 , Issue 11-12
Bulletin of the Geological Survey of Japan
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  • Yasuhiro Umeda, Satoshi Itaba
    2014 Volume 65 Issue 11-12 Pages 129-144
    Published: December 26, 2014
    Released: February 07, 2015
    JOURNALS FREE ACCESS
    This study investigates the vertical crustal movement in the period approaching the 1946 Nankai earthquake. To obtain data for just before the main shock, we examined witness testimonies on well water and sea level change that might relate to vertical crustal changes. The testimonies were taken into consideration along with existing documents and local knowledge of the inhabitants of the Pacific coast of Shikoku. The water in a few wells decreased or dried up about 1 week before the main shock. Abnormal changes in sea level were witnessed several days before the main shock. From several hours before the main shock, fishing boats returning to port could not dock at the port because the sea level was too low. On the contrary, there were also testimonies of those who noticed no lowering of sea level. The generation of a tsunami is proposed as the explanation of the abnormal changes of sea level and conflicting testimonies.
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  • Yutaka Kanai
    2014 Volume 65 Issue 11-12 Pages 145-155
    Published: December 26, 2014
    Released: February 07, 2015
    JOURNALS FREE ACCESS
    In order to obtain the geochemical knowledge of material cycle as a tracer and to contribute the concern of inhabitant about safety after the accident of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), the aerosol observation at the Geological Survey of Japan, AIST (GSJ) was continued and the new data in 2013 are reported in this paper. The Cs radioisotopes in aerosols increased a little in March 2013, then decreased from April. Those in 2012 also decreased in April, when the southerly wind often blew instead of northerly wind and rainy day increased. These facts suggest the change of weather conditions is one of controlling factors. The re-suspension of deposited particles by strong wind was thought to be more important mechanism after 2012 than the transport from the FDNPP. The Cs-137 concentration and Cs-137/Pb-210 ratio were thought to be useful parameters suggesting the re-suspension.
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