Coarse-grained Inada granite (grain size 5 mm in average) and fine-grained Oshima granite (grain size < 2 mm) samples were deformed in triaxial compression experiments. Acoustic emission (AE) was monitored using 20 transducers in real time. In each experiment, hypocenters of some thousands of events were determined using anisotropic velocity model based on measured data. The spatial distributions of AE hypocenters in both rocks had fractal structure. Their fractal dimensions were 2.3 and 2.7 in average for Inada granite and Oshima granite, respectively. Focal mechanisms of AE showed an important difference between two granites. In Inada granite, type-S (emitted by shear fracturing) was dominant throughout the fracturing process. However, in Oshima granite, fracture types were dependent on stress levels. At lower stress stage, type-C (assigned to implosive fracturing) was dominant (although only few in number). At the stress level below 80% of the fracture strength, type-T (emitted by tensile fracturing) was dominant, whereas above this stress level, type-S gradually became dominant.

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The fault plane model was constructed and the rupture process of the 1945 Mikawa earthquake (M=6.8) was determined from strong motion records. To date, two fault plane models have been reported, one of which uses geodetic data and the other the aftershock distribution. The fault plane model presented here is a thrust that strikes NNW-SSE with a small right-lateral component. It explains the strong motion records, surface fault traces, aftershock distribution, and geodetic data. Rupture started at the deepest and southernmost point on the fault plane and propagated radially. The values of the slip and seismic moment were 3.0 m and 1.0 × 10²⁶ dyne cm. The possibility is shown that the Mikawa earthquake was a multiple shock. The faulting motion of the Mikawa earthquake determined here, which is estimated to have been caused by a WWS-EEN compressional stress, cannot be explained by the stress field caused by the subduction of the Philippine Sea Plate alone. Another factor that produced a WWS-EEN compressional stress field in this area is believed to have had an important role during the stress accumulation process of the Mikawa earthquake.

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The leveling data of the network covering the Tokai district and its neighborhood, central Japan, are analyzed in order to study the vertical crustal movement in this area. Analysis is performed on the leveling data obtained during 1965 to 1985, together with the sea level data at the tidal stations along the coast within the network. In the least square adjustment of the leveling network, a new velocity model in which time change of crustal movement is taken into consideration was adopted. A comparison between the results of leveling data and of tidal data shows that the mode of vertical crustal movement at the tidal stations deduced from sea level data coincides well with that from leveling data. Based on both of them, the contour maps of vertical rate of crustal movement in the discussed area are charted for three periods: 1965-1974, 1971-1981, and 1979-1985. These maps give us a whole view of the contemporary vertical crustal movements in and around the Tokai district. The main conclusions are summarized as follows: 1) The Akaishi Mountain area and the Omaezaki area have a pattern of reverse movement, that is, Akaishi uplift corresponds to Omaezaki subsidence. This paired reverse movement seems to be a reflection of the subduction process of the Philippine Sea plate along the Suruga trough. 2) Omiya, Kofu, and the Miura Peninsula had been subsiding throughout the three periods. Especially during 1979 to 1985, the place near Omiya subsided at a rate of about -30 mm/a. The subsidences in Omiya and Kofu are considered to be man-induced ground subsidences. The steady subsidence at the Miura Peninsula can be interpreted as the result of the drag effect of the subducting Philippine Sea plate along the Sagami trough. 3) The movement at Nagoya is one of the most interesting cases. It was in a rapid subsiding state during the first period. Then the subsidence weakened, and turned to be quick uplifting during the third period. This will be also associated with unstable subduction of the Philippine Sea plate, though further study is required to interpret this abnormal phenomenon.

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