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PACIFIC SCIENCE, Vol. XXI, July 1967 
Toksoz, 1963^). Wada and Ono (1963) have 
applied the method for the Chile earthquake of 
I960. 
For the Alaska earthquake of 1964, copies of 
records from the strain seismograph at Kipapa 
Station, Hawaii, were used. This strain seismo- 
graph consists of a quartz rod 80 ft long. It 
was installed by the California Institute of 
Technology in the spring of 1963. Figure 1 
shows the traces of R 2 , R 3 , and R 4 . 
RESULTS OF ANALYSIS 
The Fourier spectra of R 2 , R 3 , and R 4 are 
given in Figure 2. To form the ratios of am- 
plitudes R 3 /R 2 and R 3 /R 4 , the decay of ampli- 
tudes with travel distance must be considered 
because the decay coefficient is frequency-depen- 
dent. The decay coefficient determined by Ben- 
Menahem and Toksoz (1963^) from empirical 
data was used for the corrections. 
The amplitude ratios of R 3 /R 2 and R 3 /R 4 
are given in Figure 3. There is coherence be- 
tween the two ratio spectra at certain frequen- 
cies. Troughs of the spectra coincide at 0.0027 
cps, 0.0056 cps, 0.0080 cps, and 0.0010 cps. 
Peaks agree at 0.0088 cps and 0.0111 cps. There 
is a peak at 0.0038 cps for R 3 /R 4 and a peak 
Fig. 1 . Upper : Phases R 2 and G 3 . Window indi- 
cates the section of R 2 that was used as data. Middle'. 
Trace of R 3 . Lower'. Trace of R 4 and G 5 . 
Fig. 2. Upper: Fourier spectrum of R 3 . Lower: 
Fourier spectra of R 2 and R 4 . The amplitude coordi- 
nate is in arbitrary units. 
Fig. 3. Directivity function, theoretical and ob- 
served. The amplitude coordinate is in arbitrary units. 
For the theoretical curve, V = 3 km/sec, 6 — 15°, 
and B — 800 km. 
