Papers in Meteorology and Geophysics

Show abstractHide abstract

On the basis of the results obtained in our preceding papers, further details of spatial distribution of aftershock activities are investigated, and in addition to the principal ones already pointed out, the following characteristics are found:
(1) The spatial distribution of epicenters of aftershocks of the Niigata earthquake of 16 June 1964 which occurred in an intermediately active seismic region shows a rather strong tendency toward clustering within the aftershock area in the initial stage of aftershock sequence. In later stages of the sequence, however, aftershocks occurred spatially rather at random though, of course, they occurred within the concentrated area, that is, the “aftershock area” over a wider range ot regions.
(2) The spatial distribution of epicenters of aftershocks of the earthquake off Ibaragi Pref. of 16 January 1961 which occurred in a region of extremely active seismic region does not show any marked difference between the initial and the later stages of the sequence, and shows slight tendency toward clustering, but this clustering tendency is weaker than that of the spatial distribution of earthquake epicenters in the normal seismic activity in this region.

View full abstract

Download PDF (1789K)

The geochemical balance and cycles of P, Si and N in the oceans are discussed taking the following items into consideration: concentration in sea water of each nutrient matter in oxidative, preformed and organic form, input from rivers, biological production and decomposition, deposition to the sea bottom and transfer between the surface and deep layers.
Results show that the remarkable difference in concentrations in nutrient matters between the Pacific-Indian and the Atlantic Ocean is mainly due to difference in the residence time of waters in deep layer in each ocean.
The residence time of deep water which is estimated on the basis of the geochemical cycles of nutrient matters is 160-270 y and 90-130 y respectively for the Pacific-Indian and the Atlantic.
To compare the biological activities on nutrient matter, a new concept, Biological Activity Index, β is introduced.

View full abstract

Register with J-STAGE for free!