測地学会誌

In the previous report, the author studied the influence of inappropriate data on the adjustment of triangulation by variation of co-ordinates. In this report, he studies the same problem for the case of net adjustment which is usually applied to the primary and secondary triangulations. The case is more complicated than the former, because the influences of inappropriate data distribute over the whole area of the net. The patern is represented by the characteristic matrix, and it is proved that there is a linear relation between the quantity of inappropriate data and their influence. These facts will offer useful information, as in the previous report, in electronic data processing.

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In succession to the preceding papers I and II in which the secular variation in the physical height of the datum was clarified in I, and the vertical movements of the earth's crust in the southern part of the Kanto district were discussed in II, the vertial move ments in the Chubu district including a part of the Kinki district are shown in this paper. The leveling surveys in this district whose survey years are shown in Table I can be arranged to 3 epochs of 1888.8, 1929.2, and 1951.1. Giving the elevations at bench marks No. 70 (Okitsu), No. 93 (Kofu), and No. 14 (Izumicho, Tokyo) which are obtained by the preceding calculations in the paper II, the leveling net of 13 loops in the concerned district is adjusted by method of the least square. The movements in the period from 1889 to 1929 is shown in Fig. 2, and that from 1929 to 1951 is shown in Fig. 3. In Section 3, general features of vertical movements in this district are discussed. The same tendency of upheaval during 66 years is seen in the areas of Suwa-Shiojiri-Matsumoto-Kakegawa-Iida-Suwa, and Komoro-Mikuni (Gunma Pref.). The same tendency of subsidence during 66 years is seen in the areas of Okitsu-Shizuoka-Fuji River, shore of the Japan Sea in Niigata Pref. and Toyama Pref., Southern part of the Noto Peninsula, and the western part of a line connecting Toyohashi, Gifu, and Fukui. In Section 4, some discussions about the relation between the vertical movements and the tectonic regions especially of the Fossa Magna are made. Abrupt movements accompanying earthquakes are briefly discussed in Section 5. Al though many earthquakes were occurred in the concerned period (Table III and Fig. 4), it is suggested that there is a possibility of detecting the movements of the earth's crust which relate to the neo-tectonic movements.

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