here indicate that the use of the average _, L. , is not valid in this 

 instance. It was considered worthwhile to give these results as an 

 indication of what had been found for one particular case. 



In the following sections, the methods of predicting and analyzing 

 power spectra will be described. The three characteristics of bottom 

 pressure fluctuations of general interest will be discussed in some 

 detail. These are the distribution of negative wave amplitudes > p^ j 

 the distribution of wave periods ^\ ^ and the distribution of a di.screte 

 negative wave amplitude, Ap with half -periods, ^t . All distributions 

 are best expressed in ogive curves. These ogive curves and various other 

 properties of pressure fluctuations will be determined and compared with 

 observed results « 



C. ffiEDICTION OF POJER SPECTRA 



For a given wind velocity, V , when fetch and duration are considered 

 unlimited, the so-called co-cumulative power spectra are defined and a 

 number of such E(+^ cjrves are given by Neumann (1953) o These curves de- 

 fine the power spectrum for each wave system with total inherent energy 



V/hen either fetch or duration of txind is a limiting factor, the energy in 

 the system also is obtainable from Neumann's curves o 



Basically, H. is proportional to the summation of the amplitudes squared 

 over the entire range of frequencies, and is equivalent to QQ~i.lAt. given, 

 respectively, by equations (3) and (5). 



For all practical purposes, the power spectruju is given by 



11 



