The present paper is the report of the studies on the abnormal propagation of seismic waves especially in K wantô district. The study was made by the precise examination of the seismometrical data observed at 25 observatories in K wantô district, upon the 48 local earthquakes occurred there in 1931. That the apparent velocity of the seismic wave differs with the direction of propagation, was pointed out by the present author.(2) Recently, Dr. H. Honda(3) treated this phenomenon quantitatively by means of measuring the deviation of the travel time observed at a certain station from the hodograph. But the numerical value of the deviation estimated by H. Honda is only a relative one. If we wish to have an absolute value of the deviation of travel time, we must measure this quantity as the deviation from the standard hodograph correspond to the given depth of seismic focus. Fortunately, H. Honda and K. Sagisaka calculated the velocities of P-wave at the successive depth of the earth crust from the observation of a few destructive ea. thquakes occurred recently in this country. Then K. Wadati and K. Sagisaka calculated the travel time of P-wave using the above-mentioned materials. The author, from the ratio of the velocities of P and S waves observed by a few authors, calculated the travel time of S wave and made the table showing the relation between the duration of preliminary tremor γ, depth of seismic focus h and the epicentral distance Δ(Tab. II). These three tables are considered to be standard at least in the present time when studying the propagation of seismic waves in our country. Next, the depth of focus of above mentioned 48 shocks were determined by means of Tab. II and the duration of preliminary tremor τo at the epicentre, which were measured from the Δ-τ diagram. Then the deviation of the travel time of P wave ΔP and that of the duration of preliminary tremor Δτ are measured by the deviation from the standard hodograph and the Δ-τ curve corresponding to the observed depth of the focus. Fig. 8 to Fig. 15 show the abnormal propagation in the Kwantô district thus observed. The figures written besides the position of the observatory denote the deviation ΔP and Δτ in seconds and the positive sign is attached to the travel time and the duration of preliminary which exceeds the standard. A simple method of determining the depth of focus by means of the radius of iso-PS line was manifested by the author a few years ago. At that time, however, the relation between the radius of iso-PS line and the depth of focus was found under the assumption of rectilinear propagation of seismic waves. Therefore, this relation was re-calculated by means of the standard travel time of P and S waves. Fig. 16 shows this relation between the mean radius of iso-PS line and the depth of focus. This relation was tested by the results of observation of 48 shocks stated above and fair agreement was proved. Also that the area of iso-PS line is closely related with the depth of seismic focus, was proved and this relation is also shown in Fig. 16. This relation is also proved to have a fair agreement with the observed results. Thus, a new method of determining the depth of seismic focus by means of the radius and the area of iso-PS line was proposed by the author as a simple and accurate one.
In this memoir the principle for the air resistance, which was adopted by the same author in the previous paper on the solution of the problem of the pilotballoon ascent in the free air, was applied on that in the calm experimental chamber. The new formula for the ascending velocity of the pilot-balloon thus obtained is as follows:- By this formula a fair coincidence of the calculated values with observed data closer than that by the formula which was reported previously by the author was found. There remains some error which seems to be systematic. With respect to this we can expect farther inprovement of the formula.
The chemical and biological observations have been carried out by us at the several stations of the River of Tama since October 1932. Water temperture, hydrogen ion concentration, free carbon dioxide, oxygen content and hardness of the water were determined at the spot of the observations and the chemical analysis on the amount of chlorine, silicate, phosphate, nitrite, nitrate and soluble organic matter being contained in the water were made quantitatively at the laboratory of the Central Meteorological Observatory. In this primary report the vertical and hourly fluctuations of these chemical components due to the invasion of the sea water were examined at the both stations of Rokugo-basi (7 meters in the maximum depth) and Yaguti (4m.). The discontenuous layers on the contents of O2, Cl and SiO2 were observed remarkably. The ratios in the mixtures of river-, sea-and rain-waters were calculated at the respective layer.
Part I. 1) New terms are introduced in the equation of motion of a viscous fluid in order to generalize Fujiwhara-Sakakibara's transverse resistance. 2) The microscopic mechanism in the fluid, on account of which the existence of the new terms are admitted of, are explained briefly. Part II. 1) It is demonstrated by making use of the new equation that: “If an incompressible viscous fluid is moving irrotationally under the influence of conservative forces, there will never arise a vortex spontaneously. But if there once occursa vortex for some extraneous reason, it can either grow or die out by itself.” 2) We know by our daily experience that if we remove the plug of a washbasin, a rotational motion of water is very liable to occur. This phenomenon is accounted for dynamically by means of the new equation of motion. 3) The difference that lies between the rôle of the ordinary viscosity and that of the new term is discussed. The former acts on the vortex so as to diffuse its vorticity, while the latter tends to concentrate or accumulate the vorticity.