Summary

Using the observed times of P, the epicenter of the very large shock of November 10, 1938, is located at 55°.3N and 158°.5W, about 80 miles to the south of the Alaskan Peninsula, in the Pacific. The time of occurrence is obtained as 20h 18m 40s, G.M.T.

Analysis of P and S residuals reveals that there were three successive shocks, the second and the third occurring 7 and 12 sec. after the first. Examination of the Indian seismograms points to a fourth shock, about 20 sec. after the first. The multiple character of the shock is brought out more conspicuously when the observed times are compared with Jeffreys' surface-focus tables and corrected for ellipticity, than when compared with normal tables. The epicenters of the first three shocks are found to be the same.

The possibility of identifying the second movement of P with sP or pP, and that of S with sS, was considered, but was found to be untenable in view of the depth of focus and available noninstrumental observations. The hypothesis of “surface focus” appears to fit in best with the present series of observations. The magnitude of the shock is calculated as 8.2.

In conclusion, we tender our respectful thanks to Dr. S. R. Savur, M.A., Ph.D. (Lond.), for his continued interest and some helpful criticisms.

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