62 MATSUYAMA, FUJITA AND HIGASHINAKA 
DEPTH OF BED ROCK 
Gradients were calculated on the assumption that a fault, the 
throw of which was large, is present along the east side of the margin 
of the basin. The variation in the observed gradients was found to 
be far too small. Therefore, the assumption was incorrect. 

Fic. 3.—Assumed structure in Suwa Basin. 
From the topography and the distribution of the corrected values 
of gradient and curvature, it seemed that the subterranean structure 
extends in the direction of the major axis of the basin. An assumed 
cross section is shown in Figure 3. By comparing the anomaly that 
arises from this assumed structure, which was computed from the 
following formula, the corrected observation values are obtained and 
the results are shown in Table III. 
I re\e p 
(= = ~) = — 2Go sin 6 cos 6 log is + sin? (a2 — x) 
Ry R: Pi 
0g ! Bat Bias. 
— = + 2Go< sin? 6 log — — sin 6 cos 6(a2 — a1) 
os Pi 
TABLE III 
Gravity ANOMALIES DUE TO STRUCTURE SHOWN IN FIGURE 3 
No. 
Place of Assumed Value Horizontal Observed Calculated 
Sta. Inclination Depth Distance Value Value 
(Meters) (Meters) 
II 275 132.4 108.5 
Akanuma 15 12°44' 313 447 92.0 IOI.2 
16 1,010 77.6 76.5 
MG) L327 36.0 46.7 
21 192 102.0 103.1 
Jingugi 20 12°44’ 173 568 50.4 72.5 
19 983 27.8 12:4 
6 308 123.2 109.0 
Uga 4 12°34’ 450 goo 94.0 94.1 
5 1,519 ° 51.0 73-9 
722 
