Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
Search
OR
Browse
Search
Volume 3 , Issue 8
Showing 1-4 articles out of 4 articles from the selected issue
    • |<
    • <
    • 1
    • >
    • >|
  • Kiyoo WADATI
    Volume 3 (1925) Issue 8 Pages 201-211
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    Some seismograms of the destructive earthquake occurred on May 23rd, 1925 in North Tazima district, show distinctly so-called the Mohorovi_??_i_??_ wave _??_. One of them is shown in Fig. (4) magnified from the seismograms of Wiechert's 200kg. seismograph installed at the Central Meteorological Observatory in Tokyo. (Epicenter distance about 450km.)
    The author of the present paper has drawn the hodograph for the longitudinal wave P from the results of seismic observations of the meteorological stations in this country as well as the time difference between P and _??_ from seismograms of these stations in case when it revealed on it. Moreover the curve of _??_ is also drawn on the same diagram and is shown in Fig. (6).
    Nextly, the author has assumed that, to interprete the time curve the discontinuity layer exists not so far from the surface in the earth crust. Following numerical values are obtained:-
    Velocity of the longitudinal wave
    above the discontinuity layer, v1=5.56km. per see.
    Ditto under the discontinuity layer, v2=7.50km. per see.
    Epicenter distance of stations where P
    and _??_ waves arrive simultaneously Δ0-120km.
    Difference of T(P)-T(_??_), shown in Fig. (6) is 6.2 sec.
    From these values, the depth of the discontinuity layer and that of the seismic foeus of this earthquake is determined. He has also compared the time of occurrence with those of the other two great earthquakes which have occurred on Jan. 15th, 1924 and Sept. 1st, 1923 respectively in Fig. (1); and ascertained that the geographical effect is not so great in these time-curves that the following conclusion may hold good in its main figure, even in any earthquake which occurred everywhere in this country.
    Followings are main results obtained in this paper:-
    (1) So called “initial movement” takes place with sudden change in its magnitude, and sometimes in direction, at the place about 100-200km. distant from the epicenter. Fig. (5).
    (2) The epicenter distance above mentioned depends chiefly upon the depth of seismic focus, therefore the depth may be estimated by this means.
    (3) I_??_itial movement must be very weak at the stations which lie within the epicenter distance, from 200km. to 1000km. approximately.
    (4) For the determination of the direction of epicenter from that of the initial movement of longitudinal wave, it is better to use _??_ phase than P and this will be done with much accuracy and easiness.
    (5) Depth of the discontinuity layer and that of the focus of Tazima-earthquakes are calculated and their values have been found to be about 42km. and 32km. respectively.
    (6) S-phase of the transverse wave begin to appear gradually o_??_ seismogram and with increasing epicenter distance it becomes more distinct.
    (7) Irregular form of isochronal curves may be considered as the effect of the discontinuity layer whose depth may not be definite in a part of the earth-crust of this part of the globe.
    (8) Well known “Omori's formula” which expresses the relation between the duration of preliminary tremor and epicenter distance, may hold good with _??_ and _??_ phases for the region of small epicenter distance and with P and L phases at distant places.
    The present paper is a preliminary report and the more complete studies will follow in a near future.
    View full abstract
    Download PDF (1728K)
  • Siro OHTI
    Volume 3 (1925) Issue 8 Pages 211-221
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    The dates of complete freezing of the river surface of Liau Ho, Ohryokuko (Amnok Gang or Yalu Kiang) Daidoko (Tai-do_??_Gang or Ta dong Kiang) Kanko (Han Gang or Han Kiang) were recorded for 20 years at meteorological stations atYingkow, Tyukotin, Ryugampo, Heizyo, and Keizyo. These are shown in table and figure in Japanese p. 213 and 214 respectively. From the curves in figure we can see that the freezing must have been controlled by the general climate of the year over the district, because the curves for all rivers are nearly parallel, showing less local influence. The weather condition before the first complete freezing were examined and it was cleared that in nearly all cases freezing took place in a calm night follow. ing a succession of NWly outbreak of cold current.
    The dates of first freezing and last melting varies generally as the latitude in this district excepting that for Ohryokuko. The date of the first freezing at Ryugampo at the mouth of the river is always earlier than that at Tyukotin situating up river in higher level and also than that at Yingkow at the mouth of Liau Ho lying farther north. These anomalies may be explained from the fact that the water flows most gently at Ryugampo.
    Remarkable fact is that there were 3 years of non freezing of Liau Ho. In these years snow fell on Mount Taiton in Taiwan (Formosa). The author's opinion for this fact is that the position of high pressure zone between the latitudes 20°to 40° shifts sometimes northwards and sometimes southwards and when it shifts to south in winter it brings cold over Formosa (lat. 25° N) with northerly winds and at the same time warmth over Manchuria with southerly currents.
    View full abstract
    Download PDF (799K)
  • Yukiti ISIMARU
    Volume 3 (1925) Issue 8 Pages 221-226
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    In August of 1924 a typhoon visited Ryukyu Islands. It strolled about the vicinity for about a week describing a very singular path having two loops. This typhoon was already reported by the Central Meteorological Obserbatry Tokyo. (1)
    Mr. Y. Horiguti precisely investigated this typhoon. (2) The author, having the intention to observe the cloud movement in typhoons with his new nephoscope, (3) had proceeded to Naha, the central city of the Islands during the vacation, and had an excellent opportunity for his purpose. The results of his observation are shown in Figures, 1 to 5 in Japanese pp. 221-226. The principal results are as follows:
    (1) The motion of clouds in every level was regular within 500km. radius from the typhoon center, angle of deviation with the isobors increasing as the height increases.
    (2) In every height the angle of deviation had a tendency to decrease as approaching to the center of typhoon.
    (3) The angles of deviation of the surface winds were less than 75°, their mean being about 50°.
    (4) The angle of deviation of the direction of lower clouds from the surface gradient was about 85° and it tended to 90° (gradient wind) as the center was approached.
    (5) It is probable that the gradient wind direction was attained at the top most layer of the lower cloud.
    (6) The angle of deviation of the direction of middle clouds from the surface gradient was about 110° in the average and that of the upper clouds was about 130°.
    (7) There was outflow of upper clouds from the typhoon region at the distance of 500km and 1000km from the center with the clockwise sense of rotation facing to the earth. As is seen on fig 4. upper cloud direction changed from east to west then again to east accompanying with the change of direction of typhoon motion.
    View full abstract
    Download PDF (305K)
  • Hidemi NAKAZIMA
    Volume 3 (1925) Issue 8 Pages 226-231
    Released: February 05, 2009
    JOURNALS FREE ACCESS
    Download PDF (432K)
    • |<
    • <
    • 1
    • >
    • >|
feedback
Top