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Volume 33, Issue 1
Displaying 1-11 of 11 articles from this issue
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Kazunari FUJII, Yoshinori NAKAYAMA, Kenji IMAI, Masayoshi NAKANO1980 Volume 33 Issue 1 Pages 1-10
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSA model experiment is performed to investigate a two-dimensional problem about Rayleigh waves transmitted across a trench. A precise measurement system is newly designed for this purpose. The transmission coefficients are defined of harmonic Rayleigh waves as well as Rayleigh pulses, respectively, whose variations with relative depth of trench are empirically obtained from amplitude spectra. It is shown that the coefficient of Rayleigh pulse can be easily derived also in case of a different sourcetime function and the source pressure with finite harmonic oscillation is taken as an example. Some distinct features are pointed out in common with these variations of transmission coefficients.View full abstractDownload PDF (1018K) -
Kazunari FUJII, Takaya TAKIMOTO, Yoshinori NAKAYAMA, Masayoshi NAKANO1980 Volume 33 Issue 1 Pages 11-22
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIt is pointed out that the transmission coefficients empirically obtained in (I) take the larger values in general those derived from theory by MAL and KNOPOFF (1965), which suggests the considerable effects of certain converted waves on behaviors of group of transmitted Rayleigh waves. An experiment denotes that two phases, SR and RS, are most significant among all the coverted waves, on the transmission along a step from elevated to depressed side and vice versa, respectively, and hence, group of transmitted Rayleigh waves consists of the following four phases; R+tr. R, RS+RRRS, SR+SRRR and SRS. The transmission coefficients of these phases are separately estimated through another experiment, sum of which almost coincides with the original coefficient in (I).View full abstractDownload PDF (1070K) -
Underground Structure Along the Line Stations from Yumenoshima, Tokyo to Enoshima, KanagawaKazuoh SEO, Hiroyoshi KOBAYASHI1980 Volume 33 Issue 1 Pages 23-36
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIt has been frequently said that seismograms obtained in Tokyo contain rather long-period components in themselves. Authors pointed out the importance to make clear extensive and deep underground structure of the Tokyo Metropolitan area, based on the experience on simultaneous observation of earthquake ground motions under the different kinds of geological conditions.
In this paper, results on the seismic prospectings in the southwestern part of the Tokyo Metropolitan area were presented. Outline of the interface between sedimentary layers and the uppermost layer of the earth's crust was shown in the form of “time-term”, along the line stations from Yumenoshima, Tokyo to Enoshima, Kanagawa. The length of this line was almost 50 kilometers long.
From the distribution of those time-terms, it was made clear that the interface mentioned above changes its depth more remarkably and rapidly, in comparison with those which obtained in other parts of the Tokyo Metropolitan area by many researchers. Most of all, Enoshima and its vicinities were confirmed to be situated on the boundary which distinguishes inner sedimentary zone of the Kanto Plain from outer outcrop zone of firm substratum.
From these results, the mechanism of formation and propagation concerning rather long-period earthquake ground motions can be expected to be elucidated.View full abstractDownload PDF (1509K) -
Hideki INATANI, Kei KURITA1980 Volume 33 Issue 1 Pages 37-49
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSTravel times and apparent velocities are measured for fifty-three Ryukyu-Taiwan-Philippine Earthquakes recorded at the Wakayama Microearthquake Observatory. Very sharp reflections from 650km discontinuity at distance range 15°-20° are found. A velocity model is given by these data. The model has two discontinuities—one is at the depth of 420km and the other of 670km. The latter is very sharp and of 10 percent velocity increase, and the former is not so sharp.View full abstractDownload PDF (1081K) -
Taro SADAHIRO, Kazuo MINO1980 Volume 33 Issue 1 Pages 51-70
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe γ-ray intensity around and about active faults are discussed from the two view points. One is the relation between γ-ray intensity distribution and active faults. The other is a variation of γ-ray intensity before and after earthquakes. The γ-ray intensity is proportional to Radon emanation which is always emanated from the Earth's surface to the atomosphere. Radon emanation is known to be large on and around the active faults. So that, survey of γ-ray intensity must be useful to search and detect active faults.
On and around several active faults, γ-ray surveys are carried out and the segments of active faults are found to be associated with large intensity of γ-ray. A few of them can be deliniated with the direction of the strikes. Some earthquakes are occurred during the surveys. Logical consideration conjectures a decrease of γ-ray intensity after an earthquake. Really, after the events a decrease of γ-ray intensity is observed for all the earthquakes. And at the time of the vibration by the blasts, γ-ray intensity shows clear decrease.
Continuous observation of γ-ray at Yamasaki Fault Observational Station supports the above observational results. These investigations give a method of studies on active faults and indicate possibility of earthquake prediction.View full abstractDownload PDF (1888K) -
Tomeo NAGAMUNE1980 Volume 33 Issue 1 Pages 71-78
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe epicentral distribution of aftershocks shows that the source region of the Izu-Oshima-Kinkai Earthquake of January 14, 1978 (origin time: 12h 24m 38.6s, 34°46′N, 139°15′E, depth: 0km), consisted of two areas, i. e., the area in the sea between Izu-Oshima and the Izu-Peninsula, spreading to the west from the epicenter of the main shock, and the one in the Izu-Peninsula, extending to the westnorthwest direction from the east coast of the peninsula.
On the other hand, it has been pointed out that the earthquake was a multiple shock, and that the second event took place about 6sec after the occurrence of the main shock (first event). The location of the second event, however, was somewhat undefinitely.
The records of the JMA 59-type electromagnetic seismographs were examined for locating the origin of the second event.
From the readings of the first arrivals of P-waves, the origin for the second event was estimated as follows:
Origin time: 12h 24m 44.5s (5.9sec after the occurrence of the main shock),
Location: 34°46′N, 139°00′E (approximately 23km west of the epicenter of thee main shock),
Depth: 0km.
It appears that the second event occurred at a place linking two source areas mentioned above, when the rupture which started at the origin of the main shock and propagated westwards, deviated its direction of propagation to the westnorthwest.View full abstractDownload PDF (701K) -
Kunihiko WATANABE1980 Volume 33 Issue 1 Pages 79-89
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThere are many cases in which microseismicities are connected with active faults. Nevertheless, investigating the spatial distribution of microearthquakes more precisely, it is occasionally revealed that some microseismicities have no clear connections with any active fault, but have some correlations to geological structure. On the basis of this observational facts, an analysis was made on the correspondence between the hypocentral distribution and the geological structure of the Hokuriku district.
As a whole tendency, microseismic activities are high in Paleozoic area and they are low in Tertialy and Quaternary volcanic area. Locally, it is recognized that Quaternary volcanic rock areas are specially aseismic and microseismic activities are found around those volcanic areas, and that the granitic areas in Paleozoic area are often aseismic. The sharp spatial contrast of microseismic activities which is not connected with any active fault seems to be resulted from the relative differences of the properties of the neighbouring rocks. The geological structure seems to be one of the control factors of microseismicities.View full abstractDownload PDF (1170K) -
Yoshimasa KOBAYASHI1980 Volume 33 Issue 1 Pages 91-94
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (492K) -
Takao EGUCHI1980 Volume 33 Issue 1 Pages 95-97
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (340K) -
Takao EGUCHI1980 Volume 33 Issue 1 Pages 97-99
Published: March 25, 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (314K) -
1980 Volume 33 Issue 1 Pages 100
Published: 1980
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (33K)
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