The best P and T axes as well as the best normals to the null directions were calculated for groups of earthquake fault plane solutions belonging to 29 areas of the Pacific Basin and vicinity. The method employed was one developed in an earlier paper of the writer; it is based on a calculation of the eigenvectors of a quadratic form. It is shown that the principal horizontal stress (PHS) directions obtained in this fashion are in excellent agreement with those obtained from other evidence. In the Western Pacific Basin and vicinity the calculations were sufficiently dense to determine PHS trajectories; the latter are shown and yield a consistent picture of the area in question.

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