Mechanism of the Hindu Kush Earthquake of Jan. 28, 1964, Derived from S Wave Data : The Use of pP-Phase for the Focal Mechanism Determination.

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The focal mechanism of the Hindu Kush earthquake of January 28, 1964 (focal depth; 207km, magnitude; 6.1, after USCGS) is discussed by using body waves. On the basis of the experimental as well as theoretical result on the phase shift of the reflected waves in the case of two-dimensional model simulating the earth by Shimamura and Sato (1965), attention is given to the use of the reflected phases for the focal mechanism study in this paper. The most probable solutions of the mechanism are numerically determined by using both the real polarization angles (ε) and the apparent polarization angles (γ), respectively, where the angle (γ) is obtained from the horizontal surface motion. The difference of the two solutions is found to be much less than the standard deviation of the solution. It is concluded that the earthquake can be explained by the double couple hypothesis since the observations of P and pP waves are sufficiently satisfied by the most probable solution determined from the S wave data alone by assuming the hypothesis. It is suggested that the use of the pP wave is serviceable to the focal mechanism determination except in the case of shallow earthquakes, while the use of the PP wave is undesirable because of its (-π/2)-phase shift.1964年1月28日に起つたHindu Kush地震(深さ207km,マグニチュード6.1)のメカニズムを実体波の観測により調べた.主な結果は次の通りである.
1967-03-31