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Volume 36, Issue 6
Displaying 1-3 of 3 articles from this issue
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Gerasimos-Akis TSELENTIS, John DRAKOPOULOS, Klisthenis DIMITRIADIS1988 Volume 36 Issue 6 Pages 255-266
Published: 1988
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSWe compute crustal thickness in Epirus (NE Greece), from spectral analysis of the Bouguer gravity field.
Moho depths were established from the slope of the log-power radial spectrum at the lower end of the wavenumber band and were found to vary from 31 to 38 km.
This is in agreement with the results obtained by other investigators employing seismological methods of analysis.View full abstractDownload PDF (1022K) -
Tetsuo TAKANAMI, Genshiro KITAGAWA1988 Volume 36 Issue 6 Pages 267-290
Published: 1988
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSA computationally efficient procedure was developed for the fitting of a locally stationary autoregressive model. The amount of computations is bounded by a function of the data length and the model order only and does not depend on the number of possible arrival times. This facilitates automatic determination of arrival time by an on-line system. The on-line system FUNIMAR (fast univariate case of minimum AIC method of AR model fitting) was developed to implement the procedure.
The method was checked by applying it to weak seismic signals from earthquakes which were superimposed with background noises such as traffic noise, electronic hum noise, and heavy microtremor. Experimental results confirm the effectiveness of the method for determining the onset time of P-wave and suggest that an AR model of the fifth order is sufficient to determine the onset time of the wave even if it is buried in considerably heavy noises. It is also shown that the onset time of S-wave can also be successfully determined by the method.View full abstractDownload PDF (1618K) -
Koji MASUDA, Hitoshi MIZUTANI, Isao YAMADA, Yasutsugu IMANISHI1988 Volume 36 Issue 6 Pages 291-313
Published: 1988
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSEffects of water on time-dependent properties of granite are investigated experimentally using partially saturated rocks. Granite specimens, all cored from the same block, were tested to failure under constant strain-rates at confining pressures from 0.1 to 200 MPa. The strain-rates in these tests were varied from 10-4 to 10-7s-1. The compressive strength decreases linearly as the logarithm of the strain-rate decreases. The strain-rate dependence of the strength is enhanced at high confining pressures. The strain-rate effect on the strength of wet granite is more apparent than that of dry granite at lower confining pressure ranges. The dilatant strain increases exponentially with applied stress except just prior to the ultimate failure. The change of the velocity during the deformation is smaller when water exists in the rock specimen than that in dry sample experiments. The acoustic emission rates are much smaller under wet conditions than those under dry conditions. Some of the present results are explained by a theory based on the subcritical stress corrosion cracking.View full abstractDownload PDF (1660K)
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