The source process of four intermediate earthquakes with magnitudes of 6.0-6.8 and focal depths between 100 and 200km has been re-investigated from the analysis of long-period P and S waveforms.
The source process times recovered from the times of the first half cycle of recorded P waves or the group delay times derived from the slopes of equalized phase spectrum show an azimuthal dependence with respect to the orientation of a nodal plane and of the null vector. If we assume shear dislocation models for these earthquakes, the dependence yields a solution to the problem of which of two nodal planes corresponds to the slip plane. Various source parameters have also been estimated from the azimuthal dependence by least squares technique.
The dimension of the slip plane or the fault length and width range in 25-40km and 8-18 km, respectively, and the rise time of dislocation is found to be about 1sec. The rupture velocity might be as low as 3.2km/sec, if two-dimensional propagation is assumed.
The theoretical seismograms of both direct P and S waves appropriate to each recording station have been synthesized on the basis of the estimated source parameters, taking into account the combined effects of wave propagation in the mantle and the crust and of the seismograph response. A good agreement of general features between the observed and synthesized waveforms on the three component seismograms gives support to the above slip dislocation model. Comparison of the amplitudes on the both kinds of seismograms yields seismic moment of the order of 1.6-3.0×10²⁶ dyne·cm and the amount of dislocation of 80-140cm. The stress drop at these earthquakes ranges from 50 to 90 bars but might exceed 170 bars for one shock. The effective initial stress to produce shear dislocations is also estimated in relation to the frictional stress on the slip plane.

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Three-dimensional model experiments broaden in principle the class of solvable problems, if compared with two-dimensional model experiments. In particular, the determination of the energy balance during the wave generation by a small explosion inside the medium becomes possible. The corresponding experiments require a well-calibrated instrumentation.
The procedure of the experiment and the calibration of an apparatus involving displacement-type transducers is described. The calibration is based on a generalization of the shake table concept to the frequency range of interest in model experiments.

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Integral representation of the static surface deformation due to a dislocation with an arbitrary orientation, at any depth, in a multi-layered medium is obtained (§2).
A part of the integrand is approximated by an analytical function by applying successive least squares approximation and the integration is performed (§3).
By designating the fault parameters, such as fault depth, fault length, fault width, slip angle, dip angle and the spacial distribution of the dislocation over the fault plane, the surface deformation is evaluated by numerical integration techniques.
The purpose of this paper is not to find the general features of deformations due to various fault models but to establish several machine compution techniques, hence only a few examples of numerical computations are presented.

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In order to study whether or not the elastic shocks can be radiated from the material undergoing phase chnage, an experiment was carried out by the use of NH₄F for the working material. NH₄F changes the crystal structure at about 3.8kb and at room temperature. An amount of volume change at this phase change is about 28 percent. When the polycrystalline NH₄F specimen was supercompressed or superdecompressed, a sudden shock occurred followed by many rectangular pulses with a short pulse width of about 50 milliseconds. After these shocks propagated in the pressure medium, a shock with a large pulse width of about 2 seconds appeared. This last shock seems to have been due to the absorption of a high frequency component. The direction of initial motion for the shock at the phase change from a low pressure form to a high pressure form is opposite to that for the shock at the phase change from a high pressure form to a low pressure form. This fact shows that the shocks were caused directly by the volume change at the phase change. These elastic shocks seem to occur because of the properties of the large hysteresis in NH₄F on the transition pressure of phase change.
The number of shocks at the phase change was counted. By the use of the relation between the cumulative number of shocks and time, the reaction rate at the phase change of NH₄F was calculated based on the theory of reaction kinetics. If the reaction rate is represented by the equation; dX/dt=K(1-X)^p, where X is mole fraction of product, t is time, K is the reaction constant and p is the order of reaction, p_??_1 and K_??_10^-1/sec. The equation where p=1 means a first order reaction in terms of reaction kinetics.

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Tilt observations from nearby local earthquakes in the magnitude range from 3 to 5 and larger teleseisms show an amplitude reduction with epicentral distance R of the form A (in seconds of arc)=10^M-4.1×R^-1. The result is compared to static elastic dislocation models. Velocities of the tilt propagation are in the range 2.1 to 2.8km/sec for near earthquakes (focal point to station), and up to 3.3km/sec for teleseisms. In view of the discrepancies between strain and tilt observations and static elastic dislocation theory, the tilt reduction with distance, and the propagation velocities, the strain and tilt steps are viewed as a surfacetype propagation phenomenon.
The earthquake-associated tilts and first motions imply a south-southeast to north-north-west compression along the northern edge of the Tanana Basin. Earthquake locations and depths indicate active faults south of Fairbanks along the northern edge of a gravity low, along the Chatanika River, and on the northern extension of the Minto fault. The first two of these faults have not been known before.

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One of hypotheses for deep earthquake generation is a phase change hypothesis. In order to examine this possibility, we studied the reaction rate for the phase change from nickel olivine (Ni₂SiO₄) to nickel spinel (Ni₂SiO₄) under high pressure and high temperature by the use of tetrahedral press.
The reaction rate is expressed by the equation: dX/dt=K(1-X)^P, where K is the rate constants, X is the amount of product, t is time and p is the order of reaction. The rate constant K is given by the equation: K=K₀(KT/h) exp (-ΔAE/kt)sinh(αΔP/KT), where K0 is a constant, T is the absolute temperature, k is the Boltzman constant, h is Plank's constant, ΔE is the activation energy, ΔP is the deviation of pressure from the eqgilibrium state and α is a constant. If (αΔP/kT)<<1, the above equation becomes K=K0(αΔP/h) exp (-ΔE/kT).
We obtained such a result that if the phase change of olivine-spinel was a first order reaction in terms of reaction kinetics, the rate constants K for 800°C, 40kb, for 900°C, 40kb and for 1000°C, 40kb became 10^-3/min., 6×10^-3/min. and 2.3×10-1/min. respectively.
Based on the above equation and experimental results, we obtained the result that when ΔP=1kb and T=1300°C, 80 percent olivine would be converted into spinel within 15 seconds. This rate of phase change seems to be so rapid as to cause an earthquake.

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