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Volume 20, Issue 3
Displaying 1-7 of 7 articles from this issue
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Kyozi TAZIME, Hiroshi OKADA1967 Volume 20 Issue 3 Pages 153-163
Published: October 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSFollowing the previous paper (TAZIME (1966)), numerical calculations have been carried out with the electronic computer. Conformal mappings of wave number ξ on frequency ω-plane are obtained in which γ=ω/ξ was used as a gobetween. Complete RIEMANN sheets have not been constructed. Only a cut runs from one of singular points parallel to the imaginary axis. Overlaps of ξ on ω-plane are avoided by the cut. Two sheets thus decided correspond in some respect to those exhibited by GILBERT (1964). A higher mode has been also investigated in connexion with the ground mode. Using the present mappings, the contour integration on ω-plane may be executed along any path, for instance not only the path of the stationary phase but also that of the steepest descent, when complete RIEMANN sheets will be obtained.View full abstractDownload PDF (749K) -
Tokutaro HATORI1967 Volume 20 Issue 3 Pages 164-170
Published: October 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSBoth of the severe tsunamis of 15 June 1896 (tsunami magnitude: 4) and of 3 March 1933 (tsunami magnitude: 3) were generated off the Sanriku coast of north eastern Japan. Although the magnitude of 1896 Earthquake (M=7.6) was smaller than that of 1933 Earthquake (M=8.3), the intensity of 1896 Tsunami was much larger than that of 1933 Tsunami, particularly along the northern part of the Sanriku coast. In order to explain this different behaviors of these two tsunamis, tsunami sources are estimated by means of an inverse refraction diagram and the spectral analyses of records at three stations are made.
It is found that the tsunami source of 1896 lies close to the northern part of the Sanriku coast with the major axis of the source directed in NNW-SSE, in contrast to the source of the 1933 Tsunami which lies some 110km from the coast with the axis in N-S direction. Sea level disturbances at the margin of the sources for the tsunamis of 1896 and 1933, estimated on the basis of the shoaling coefficient and the inundation heights of tsunamis along the coast, seem to be about 2m and 1m respectively.
In addition, the source area of the weak tsunami of 21 March 1960 is estimated. The earthquake magnitude is M=7.5 and this source includes the area of aftershock activity extending about 120km in an elongated shape.View full abstractDownload PDF (654K) -
Yasuo SATÔ, Yoshiko KOTAKE1967 Volume 20 Issue 3 Pages 171-179
Published: October 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe accuracy of the determination of earthquake parameters is strongly governed by the geographical distribution of seismic stations and the epicenter. In order to estimate this effect quantitatively, the distributions of the expected error of the epicenter location and the origin time of earthquakes are calculated by the Monte Carlo method. As the observation points 124 standard stations are assumed which belong to WWSSN, though only the ones with epicentral distance <105° are actually adopted. As the observation errors at each station normally distributed random numbers are used with the mean value 0 and the standard deviation 1.0sec. Similar calculations are repeated 400 times for each assumed epicenter which is distributed on the earth's surface with the interval of 10° both in latitude and longitude (except the area near the poles). The result is shown in the form of figures.View full abstractDownload PDF (875K) -
Hikaru WATANABE, Akio KUROISO1967 Volume 20 Issue 3 Pages 180-191
Published: October 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIn August 1965, the co-operative observations of microearthquakes were made by the Research Group for Ultra-microearthquakes at 10 temporary stations and also at 12 routine stations of the Earthquake Research Institute of the University of Tokyo, spread widely over Wakayama District, Central Japan. The seismographs and the method of observation were almost the same as we had used in the previous co-operative observations at Gifu and Fukui Districts.
As a result of the observations, we could confirm that the area concerned was divided into several seismic active regions according to the spatial distribution of foci of the microearthquakes. Besides the problem on seismicity, several properties regarding the generation mechanism of local earthquakes, the earthquake sequence and the anomaly in travel time curve were studied in some detail in comparison with the previous results by many authors on the area concerned.View full abstractDownload PDF (998K) -
Yasuo SHIMAZU, Tatsuo URABE1967 Volume 20 Issue 3 Pages 192-197
Published: October 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSTo explain a sharp peak of the surface heat flow distribution at the oceanic ridge, magma ascending accompanied by the mantle convection is considered. When the temperature rises beyond the melting point of basalts, magmas are assumed to be generated. A thermal effect of latent heat is taken into consideration. The magmas thus generated are moving with the convection current, or are ascending either by zone melting or by effusion. Secular variations in the distribution of the surface heat flow and in the position of magma reservoirs are shown for a two-dimensional current with 1000×400km scale. It is not shown that magmas can be generated at the sinking region. A similar calculation is carried out for the non-Newtonian fluid by an approximate method.View full abstractDownload PDF (439K) -
Takuo MARUYAMA1967 Volume 20 Issue 3 Pages 198-202
Published: October 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (468K) -
Yoichiro FUJII1967 Volume 20 Issue 3 Pages 202-203
Published: October 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (151K)
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