Migration velocity analysis is investigated to obtain a long-wavelength velocity model for a complex structure. Residual wavefront curvature analysis is combined with prestack reverse-time depth migration to update the velocity model as well as the image of the subsurface structure. The imaging point for a given velocity error is solved rigorously in the case of a dipping layer. Convergence behavior is examined by three synthetic examples in an iterative scheme in which the depth and velocity are modified interactively. A stable solution can be obtained by smoothing the model space with an appropriate window length. It was found that the velocity is modified from the shallower part to the deeper part gradually, and that the number of iterations that is necessary for convergence is correlated with the ratio between the target depth and window length of the moving average. In a field example of land survey conducted around a buried fault zone, lateral variation of velocity was successfully detected. With the final velocity model and final seismic section, this method provides more reliable interpretations than the CMP stacking method.

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By modifying Uffen's approach, which relates the Einstein-Debye theory of solids to Lindemann's melting criterion, the relative melting temperature distributions in each major division of the Earth's interior are calculated from observed seismic velocities. With further assumptions, the melting temperature profile and three possible present temperature distributions inside the Earth are also proposed. By extrapolation, this approach yields a temperature of ≤8, 000 K at the center of the Earth. On the basis of the melting temperature gradients at each major seismic discontinuity, it is concluded that only the 220- and 400-km seismic discontinuities are consistent with a phase transition possessing a positive Clapeyron slope, whereas all other seismic discontinuities are found to be consistent with either a phase transition having a negative slope or a chemical change. The outer-inner core boundary is not a simple melting phenomenon. These conclusions have been reached independently of all previous studies that used elastic and thermal properties of the Earth and of the predicted compositions for the various parts of the Earth.

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A method is developed to simultaneously determine both the elastic constants and asphericity of a spherical specimen by the resonant sphere technique (RST). First, a numerical test is presented to examine the possibility of simultaneous determination of the specimen's elastic constants and asphericity by an inversion analysis of the resonant frequencies measured for the specimen. Then, the method is applied to elasticity measurements of a spherical olivine specimen with small asphericity. The simultaneous inversion analysis method allows one to evaluate elastic constants and asphericity more accurately than the previous method, in which the asphericity and elastic properties are separately determined. Since the asphericity of a spherical specimen has a noticeable influence on the calculated elastic constants, simultaneous inversion is an effective method to obtain improvements in the accuracy of the elastic constants and to quantify the asphericity of the specimen by the RST.

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In the case of GPS relative positioning, the errors in baseline vectors can be divided into constant and distance-dependent parts. Each component does not reflect a single error source, but a combination of error sources. This paper deals with the determination of the coefficients of constant and distance-dependent parts using observed data with the aid of Minimum Norm Quadratic Unbiased Estimation (MINQUE). These two coefficients are determined for a network of short baselines where the baseline lengths range from 35 to 130 km, and also for a network of long baselines ranging from 40 to 1, 600 km. For different networks, we get different values for the constant part, which depends on the type of observation, the types of receivers, the shape of the network and so on. We demonstrate how the distance-dependent part varies with the, baseline length. As in the case of the constant part, the estimated value of the coefficient of the distance-dependent part is different for different networks. However, it is shown that this coefficient is less than 1 ppm for the networks of longer and shorter baselines, and decreases with increasing baseline length.

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Recent studies on basin-induced surface waves observed in deep earthquake seismograms at basin stations have shown that the excitation strength of the surface waves varies with earthquakes, as well as the basin shapes. We investigated the variation in basin-induced surface waves with earthquakes by a combination of observational and numerical studies, selecting the Tokachi Basin, Hokkaido, Japan, as the test site. A detailed comparison between the seismograms observed at the basin and rock sites for nearby and intermediate-depth earthquakes shows that the excitation strength of basin-induced surface waves with a predominant frequency of about 0.3 Hz strongly depends on the frequency content and incident angle of S-waves impinging on the basin. The observational results are complemented with two-dimensional modelings of SH and P-SV wavefields using the pseudospectral method, which successfully reproduce the effects of the frequency content and incident angle of incident S-waves. The simulation results also show that the basin edge slopes play an important role in the excitation of basin-induced surface waves.

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