Diffusion of Ti^es Into the Volcanic Rock of Hawaii; A Method For 

 Estimating Subsurface Fenneability 



Records of water level have been obtained from the irrigation 

 wells on the island of Maui, T. H., at distance from 0.8 to ii.3 km. from 

 the coastline. Harmonic analyses of these records reveal diurnal and semi- 

 diurnal components o With increasing distance from shore, the atiplitudes 

 of these components diminish, and the time of high water is increasingly 

 retarded. This diffusion-like behavior can be accounted for by a mathematical 

 analysis of the problem. The agreement between theory and observations is 

 only fair, but nevertheless the method may have some value for roughly 

 estimating subsurface permeability. 



This investigation has been conducted jointly with Prof. George 

 Carrier at Brown University, and Mr. Do.ak Cox at Honolulu, Hawaii. 



Tsunami of h March 19^2. 



Tsunami waves from the Japanese earthquake of h March 19^2 have 

 been recorded on the "tsunami recorders" located at La Jolla and Oceanside, 

 California. The amplitudes were 1 inch at La Jolla, 1.5 inches at Oceanside. 

 The period was imusually long, about 30 minutes. The waves are so low 

 that they are only faintly recognizable above liie usual background. The 

 amplitude at Honolulu was 6 inches. The great reduction in amplitude between 

 Honolulu and California has been considered. It is believed that the most 

 likely explanation is a partial reflection from the continental shelf off 

 California. A brief manuscript has been submitted to the Seismological 

 Bulletin. 



A Method for Recording Non-Astronomic Tides - 



By means of suitable linear combinations of hourly tidal heights 

 the astronomic tides can be greatly suppressed, and fluctuations of non- 

 tidal character can be studied. Attempts are now being made for develop- 

 ing three such "mathematical filters," 



sub -tidal recorder: periods 6 to 12 hours 

 intra- tidal recorder: periods 12 to 21; hours 

 trans-tidal recorder: periods longer than 2k hours. 



The sub-tidal recorder begins at the longest periods conveniently measured 

 by means of the tsunami recorder. We are now determining the optimum 

 linear combinations to give the above filter characteristics. The pro- 

 cess involves many matrix inversions and matrix multiplications. Some 

 of the matrices are now in the process of being inverted by automatic 

 computing machines at the U, S. Navy Electronics Laboratory, Once these 

 combinations have been derived, they can be used for any tide station. 

 Starting with hourly tide values, and applying the formulae, the non- 

 tidal oscillations can be computed. The method is adapted for punchcard 

 systems, 



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