Elastic constants of three natural pyrope-almandine garnets (Fe/(Mg+Fe)=0.18, 0.48 and 0.58) were measured by an RPR method in the temperature range between -190° and 80°C. The temperature derivative of bulk modulus ∂K_s/∂T does not depend much on the composition, but those of shear constants ∂C₄₄/∂T and∂C_s/∂T [C_s=(C₁₁-C₁₂)/2] increase considerably with increase in the Fe-content. The temperature derivatives of the elastic constants (kbar/deg) of pyrope and almandine at room temperature are determined by extrapolation:
From the measured elastic parameters of garnet, the material of the high velocity layer (V_p=8.6km/s and V_s=4.9km/s) in the oceanic lithosphere is interpreted as eclogite or garnet peridotite constituted dominantly of garnet.

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Mechanism Studies fox five destructive earthquakes in the Izu peninsula, central Japan, since 1930 were made on the basis of an extensive set of P-wave first-motions, aftershocks, close-in long-period seismograms, leveling, triangulation and field data. Physical source parameters such as dislocation, source dimension and seismic stress were determined for the Northern Izu earthquake of 1930 (M=7.0), Southern Izu of 1934 (M=5.5), Izu-Oki of 1974 (M=6.9), Amagi of 1974 (M=4.9) and Kawazu of 1976 (M=5.4). All of these earthquakes represent a purely or nearly vertical strike-slip faulting at a very shallow depth. These faults constitute a system of conjugate faults produced by a single force system, e.g., north-south compression, with the exception of the northern fault of the 1930 Northern Izu earthquake which indicates NW-SE compression. The strikes of the faults coincide closely with a general trend of geologically active faults in this area. The stress drop varies from 10 to 70 bars, and larger shocks indicate larger stress drops. The dislocation velocities for the three small shocks are low, about 10 to 15cm/sec, in good agreement with their low stress drops.

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Six shallow earthquakes, which occurred in the Sanriku-Oki region during the period from 1965 to 1970, are studied by using long-period P-and S-waves. Focal mechanism solutions are determined from the S-wave polarization angles. Fault planes, which are distinguished from the auxiliary planes by means of the hypocenter distribution of aftershocks, are slightly dipping toward the island arc. A linear correlation is found between the dip angle of fault plane and the distance of epicenter from the trench axis; the dip angle increases with increasing distance. The motion directions of the foot wall blocks relative to the hanging wall sides are in the range from N58°W to N72°W and are consistent with the expectation from the plate tectonics theory, the motion direction of the Pacific plate relative to the Eurasia plate. The focal depths re-determined by the use of depth phases such as pP and sP reveal that the hypocenters of the six earthquakes lie almost on a plane slightly dipping toward the island arc.
The spectral analysis of P-waves is made to elucidate the dynamic source process. To do this, the effects of multiple reflection in the crust near the source region as well as beneath the station are taken into account. A unilateral bidirectional model of faulting appropriate to each event is determined by comparing the trough frequencies in the observed P-wave spectra with those expected theoretically. The fracture is found to have propagated in the motion direction of the foot wall block with a velocity between 2.0 and 3.1km/sec.

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Six explosions ranging from 300kg to 600kg and a quarry blast of 7.5 tons in and around the Shizuoka district were observed within distances less than 150km from the shot points for refraction surveys of the crust in this province. As the geological structures in the Shizuoka district are highly complex, the shooting and the recording had to be made in various geological formations, which gave rise to difficult conditions that all seismic rays consisted of complicated paths. Accordingly, some of the results obtained by the experiments so far made near this region were also incorporated into this study. Combination of our experiments and those made by other researchers, in spite of short distances of observation lines, enables us to propose a four layered crustal model on the uppermost mantle.
The main features of the model obtained here are as follows: (1) The east side of the Median Tectonic Line is depressed by about 5.7km and covered with thick surface layers. (2) The upper boundary of the granitic layer is expected to be upward convex beneath the western Izu Peninsula at a depth of about 2km. (3) The basaltic layer has a thickness of about 15 km. (4) The Moho is estimated as 33km deep beneath Suruga Bay.

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