抄録
The torsional free oscillation due to a dip-slip fault or a strike-slip fault is studied in an earth model with homogeneous mantle and homogeneous liquid core. Because of the simple earth model assumption, only the fundamental mode of order number two, 0T2, is investigated.
It is found that the 0T2 is effectively excited by a vertical strike-slip fault. The surface amplitude of the free oscillation due to a horizontal or a vertical dip-slip fault is about three percent of that due to a vertical strike-slip fault. Radiation patterns, except for a horizontal or a vertical dip-slip fault, are governed by P22 (cos θ) (cos 2ψ sin 2ψ).
If a step function time variation fault is assumed, then the maximum surface amplitude of 6×10-2cm is estimated when the area of the fault is 104km2 and the mean offset over the fault-plane is 5m.
