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Volume 27, Issue 1
Displaying 1-13 of 13 articles from this issue
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Hiroo WADA, Yoshimichi KISHIMOTO1974 Volume 27 Issue 1 Pages 1-9
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSRoutine observation of microearthquakes in the vicinity of the Atotsugawa fault in the Chubu District has been carried on by the Kamitakara Crustal Movement Observatory, Kyoto University.
Microseismicity in this area seems to consists of three groups; namely, 1) a linear arrangement of microearthquakes along the Atotsugawa fault, 2) a large scale block of microearthquake occurrence extending from Mt. Norikura to Takayama, and 3) a distribution of N-S direction along the Central Mountains.
The linear distribution of microearthquakes along the Atotsugawa fault is particularly remarkable, which is the same properties as those along the strike-slip faults in northwestern Kinki District. Superposed push-pull distributions of the initial motion of P waves of these earthquakes seem to indicate that the general tendency of the tectonic compression acting in this area is nearly in horizontal and E25°S-W25°N direction.View full abstractDownload PDF (753K) -
Tokutaro HATORI1974 Volume 27 Issue 1 Pages 10-24
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSSource areas of the 1944 Tonankai and the 1946 Nankaido tsunamis are reexamined on the basis of tide gauge records and visual observations. The height distribution of three large tsunamis accompanying the giant earthquakes in 1707 and 1854 (two tsunamis on 23 and 24 December) are summarized from old documents and the source areas of these tsunamis are estimated. These tsunamis are very large tsunamis (Imamura and Iida's magnitude m=2.5-4) generated along the Nankai trough since 1700.
For the 1946 Nankaido tsunami, the subsidence of the sea-bottom may have occurred in the shoreward area and the tsunami source in the west side may be effectively uplifted, judging from the initial motion of tide records and geodetic data. The uplifted area of tsunami source is almost the same as Omote's result (1947). The elongated source area of the 1944 Tonankai tsunami along the Kumanonada agrees approximately with the aftershock area. The shoreward sea-bottom in the tsunami source is subsided. The inundation height and seismic intensity distributions at the Tokaido district for the 1854 (on Dec. 23) tsunami are larger than those of the 1944 tsunami, suggesting the difference of the source locations of two tsunamis. In case of the 1854 (on Dec. 24) tsunami, seismic and tsunami intensities along the Nankaido district are larger than those of the 1946 tsunami but the distribution patterns are similar to the 1946 tsunami and the source locations of two tsunamis are approximately estimated in the same region. The source areas of these tsunamis extend 200-250km along the Nankai trough. On the other hand, the source dimension of the 1707 tsunami seems to be of the order of 500km. The distribution pattern of inundation heights for the 1707 tsunami seems to be similar to the sum of two tsunamis of 1944 and 1946.View full abstractDownload PDF (1599K) -
Hisaya YOSHIOKA, Masayoshi NAKANO1974 Volume 27 Issue 1 Pages 25-41
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSA theory is proposed about the strain in the earth's crust due to the periodic (annual or daily) variation of surface temperature.
From the equations of heat-conduction and of motion in thermoelastic solid the exact solution is firstly given in integral form, whose approximate expression is then derived, by taking account of the magnitudes of physical constants. Particularly, about the surface temperature with amplitude varying discontinuously at a point, the fields of strain and temperature are explicitly obtained by the method of steepest descent. The solution can be extended to the case that the amplitude varies continuously in an interval. It is pointed out that the strain is separated into two terms, one of which, though having a large amplitude in shallow range, rapidly attenuates with depth, while the other is slow to attenuate, with a small amplitude from the first.
The former is regarded as the strain due to heat-energy conducted to the point of observation and the latter is purely an elastic deformation propagating as body-waves from the discontinuous point. Comparison with the observed results confirms this separation of strain, to some extent.View full abstractDownload PDF (1392K) -
Kiyoo WADATI, Matsuo TAKAHASHI1974 Volume 27 Issue 1 Pages 42-56
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIn the present paper the underground structure peculiar to Japan and its neighborhood is dealt with, based on the seismic activity in Japan and neighborhood, especially taking account of the fact that each of the seismic activity area and the seismic inactivity area shows in the subterranean space its respective space, and adding the authors' investigational result to the fruits of researches hitherto.
Main results of the present paper are:
(1) The seismic activity area was divided into 3 zones: the shallow earthquake zone (particularly the existence of “a thick shallow earthquake zone”), the joint earthquake zone and the deep earthquake zone.
(2) A concept that the seismic activity zone can be regarded as “the crust” has been proposed.
(3) From the discussion of the travel time residual and the area of abnormal distribution of seismic intensities, the values of Low V and Low Q of the seismic inactivity area were obtained, and in particular the stronger point of that property was found at a comparatively small depth in the underground on the continental side along the volcanic front.
(4) The mantle flow in Japan and neighborhood is assumed to be composed of its main flow (along the deep earthquake zone) which flows descending from the Pacific side to the continental side and from east to west, of a weak flow northward in the offing of Tosa and in Enshu-nada, and of flows eastward and southward from the direction of the Sea of Japan.
(5) In general, where the mantle flow ascends, there exist Low V and Low Q and the area is related to volcanic activities, and where the flow descends, the area is related to the seismic activity area.
(6) The joint earthquake zone is an area of the strongest seismic activity, and is closely related with large-scale earthquakes.View full abstractDownload PDF (1588K) -
Hideyuki FUJISAWA, Hajimu KINOSHITA, Takeshi HACHIMINE1974 Volume 27 Issue 1 Pages 57-64
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSElectronic circuits for the measurements of velocity and attenuation of elastic waves are outlined. Two modifications are proposed. These are essentially apparatuses for the pulse-superposition method and used for the measurements in minerals. First of them gives output voltage of about 60 (P-P) of RF burst with varying carrier frequency of 10-50MHz. The other one provides a similar output with a fixed carrier frequency of 10MHz. Latter one is advantageous for attenuation measurement due to easy impedance matching of whole system for detection of very weak reflection of waves.
Since a principle of this sort of circuits are well known, the present paper will provide only a practical guide for construction of the circuits.View full abstractDownload PDF (630K) -
Jyun-ichi MAEDA1974 Volume 27 Issue 1 Pages 65-74
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe elastic shocks caused by the creep fracture of granite under confining pressure have been investigated. The experimental results obtained up to the present were summarized. The principal results are as follows: 1) The procedure of creep fracture was very difficult for the delicacy of the establishment of constant stress, and this tendency seemed to be remarkable as confining pressure was increased. Smooth creep fracture was accompanied by many foreshocks, on the other hand, in the comparatively sudden fracture caused by the failure of the establishment of delicate constant stress, a few and small foreshocks were only observed. 2) The aftershock sequence under the experimental condition similar to the image of aftershock occurrence in the natural earthquake was obtained, and the Omori's aftershock formula was found to be well applicable to the sequence.View full abstractDownload PDF (736K) -
Junzo KASAHARA, Syozaburo NAGUMO, Sadayuki KORESAWA, Toru OUCHI1974 Volume 27 Issue 1 Pages 75-77
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
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Yutaka OHTA, Takashi SUGIYAMA, Hiroshi SEKIGUCHI1974 Volume 27 Issue 1 Pages 78-81
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
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Resistivity Changes Associated with Large Earthquakes as Observed by a Resistivity VariometerYoshio YAMAZAKI1974 Volume 27 Issue 1 Pages 81-83
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (397K) -
Toshi ASADA, Hideteru MATUMOTO1974 Volume 27 Issue 1 Pages 83-85
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
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Hitoshi TAKEUCHI1974 Volume 27 Issue 1 Pages 85-87
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
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Hitoshi TAKEUCHI1974 Volume 27 Issue 1 Pages 87-88
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (261K) -
Masakazu OHTAKE1974 Volume 27 Issue 1 Pages 88-90
Published: March 30, 1974
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (224K)
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