the tide level prevailing at the time of the highest wave or waves of the 

 tsunami must be subtracted. Figure 82 suggests that south of Crescent 

 City and Fort Bragg the tsunami waves arrived on a falling tide 1 to 2 

 or more hours after high tide, which caused a natural lessening of the 

 runup potential. The approximate tidal ranges from Monterey to Crescent 

 City are shown on the cotidal lines in Figure 82. Supporting data for 

 Figure 82 (from Magoon, I965) are included in Table B-5 of Appendix B. 



The behavior of San Francisco Bay has already been discussed in 

 Section II-6. Particulars of the attenuation of the tsunami waves in 

 the bay in relation to unit amplitude at the Golden Gate (cf . Magoon, 

 1965) are in the inset to Figure 82. 



In Monterey Bay, about 60 nautical miles south of San Francisco, 

 the tsunami produced widely different effects at the north and south 

 extremities at Santa Cruz and Monterey. Santa Cruz experienced a runup 

 almost twice that at Monterey despite the apparently protected setting 

 of Santa Cruz in relation to the approach direction of the tsunami. The 

 reason may perhaps be ascribed to the deep and narrow canyon that vir- 

 tually bisects the bay (Figure 83) and favors refraction of wave energy 

 entering the bay more toward the north than toward the south (Wilson, 

 et al, 1965). 



Monterey Bay provides another case for assessing the effects of the 

 tsunami in stimulating local resonances. The peculiar planform of the 

 bay aniits bathymetry (Figure 83) discounting the canyon, is well ap- 

 proximated by a circular quadrant basin with a paraboloidal bed (or even 

 a conical bottom). Using this geometrical analogy, the solutions for 

 applicable modes of oscillation of the bay can be deduced from Lamb (1932) 

 (cf. Wilson, et al, I965, Wilson, I966) and are illustrated in the se- 

 quence of Figure 81+, which applies to a quadrant basin of 2^+0 feet uniform 

 depth and 100,000-foot radius (Figure 83). Figure 8kd may be considered 

 to approximate the fundamental-mode oscillation for the Continental Shelf 

 and bay with a node at the edge of the Continental Shelf. However, to a 

 good approximation also. Figure 81+a could be considered fundamental to 

 the bay; and its Continental Shelf, to the edge of the deep canyon. The 

 two cases yield widely different periods, the first about 65 minutes, the 

 second about 31 minutes. The other modes of oscillation in Figure 8U 

 involve nodal circles or nodal diameters or combinations of both. All 

 of the nodes might be considered realizable as possible ways in which 

 Monterey Bay could respond to excitation at its lowest frequencies. 



That the bay did appear to oscillate in some of these modes is 

 evident from Table IV, which compares observational deductions with 

 theory. This table includes spectral analyses of the tsunami records 

 at three locations in Monterey Harbor (Marine Advisers, I96I1). In the 

 lowest modes these show noticeable peaks at 33.3 and 16.7 minutes. The 

 resolution, however, was poor at low frequencies and failed to show 

 longer period effects. For comparison in Table IV, results are drawn 



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