66 EIGHTH PACIFIC SCIENCE CONGRESS 



It has been a common sense that the tsunami wave becomes highest 

 at the head of a bay. But, according to the observed data of the San- 

 riku Tsunami, March 4, 1952, this was proved not to be necessarily the 

 case. To explain this fact, Ichiye assumed a frictional resistance on the 

 bottom of the bay head and had the conclusion that the amiplitude be- 

 comes a maximum at the middle portion of the bay (KMOM, 10, 1952). 



Although these papers are very excellent, it might be more advis- 

 able now to have a tsunami recorder and to analyze the records more in 

 detail. D. Shimozuru and T. Akima found tsunami waves of long 

 period, about 80 minutes, superposed on shorter period waves of tsu- 

 namis in the tidal record of December 21, 1946, by means of mechanical 

 law-pass filter of torsion pendulum type. The investigation of the phase 

 of the long period waves appears to indicate that they are due to the 

 reflection from Guam Island (ERIE, 30, 1952, 223-230). 



The accounts on the Sanriku Tsunami, March 4, 1952, have been 

 published by several authorities including the Earthquake Research In- 

 stitute and Geophysical Institute, Tokyo University, and the Central 

 Meteorological Observatory, and others. In the Geophysical Institute, 

 Tokyo University, an expedition was issued for the investigation and 

 the report on tsunami waves and its patterns was published by K. Yoshi- 

 da, K. Kajiura, and H. Miyoshi (JOSJ, 8, 1953). An importance of 

 the reflection of tsunami waves by continental slope was pointed out in 

 this report. In the case of this tsunami, a warning system was success- 

 ful. Various problems having been discussed concerning the propaga- 

 tion of tsunami waves (T. Ichiye, US, 26, 1949; T. Ikano, CKH, 2, 1950; 

 S. Homma, KS, 28, 1950; T. Rikitake, ERIE, 29, 1951), interesting is 

 an application of diffraction problem to tsunamis which was made by 

 K. Hidaka and S. Hikozaka concerning a distribution of wave-height 

 on the coasts of Kausi Island in the case of the Hawaiian tsunami of 

 1946 (JO, 5, 1949). Similar discussion was also made by S. Homma 

 (GM, 21, 1950). Contributions were also made by model experiments 

 of tsunami which S. Ogiwara, and T. Okita attempted (CKH, 2, 1950; 

 SRTH, 2, 1950). 



It should also be mentioned that records of the sea shock on Au- 

 gust 10, 1949, were obtained by S. Takagi, using a seismograph installed 

 on board an anchored ship (US, 27, 1950). Another important work 

 is a theoretical discussion of flood waves by S. Yayami, the importance 

 of lateral mixing being introduced (Disaster Prevention Res. Ins. 

 Bull., 1, 1951). 



Marine Meteorology 



In 1950, Arakawa made a statistical survey of the visibility in the 

 Northwestern Pacific Ocean using the data observed by the Japanese 



