The First Motion in Longitudinal and Transverse Waves of the Main Shock and the Direction of Slip

Abstract

Data on compressions and dilatations in the direct longitudinal waves are given and used for the determination of the fault plane at the starting point of the earthquake and for the finding of the direction of slip. A method is developed to get similar information from the first motion in transverse waves recorded at stations in the hemisphere around the epicenter and is applied to observed amplitudes which are listed. The final results are: at the depth of the source (about 10 miles) the fault plane has a dip of about 60° to 66° towards E 50° S ; the slip along the fault at this depth was roughly up towards north in the upper (southeastern) block relative to the lower (northwestern) block; the vertical component of the slip was about 1.4 times that of the horizontal; the horizontal component corresponds to a relative movement northeastward in the upper block (southeast of the fault), southwestward in the lower block.

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