Phases in the Preliminary Tremors of Seismograms and Crustal Structure in Nagoya District
1959 Volume 12 Issue 2 Pages 75-81
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1959 Volume 12 Issue 2 Pages 75-81
Some phases in the preliminary tremors of seismograms recorded at Nagoya and Gifu are investigated. The seismograms of the aftershocks following the Mikawa earthquake of 1945 were used. The phases obtained are explained as due to P2 S1 waves which were investigated by Matuzawa and others for Kwanto district.
The existence of two distinct phases, denoted by P1 and P2, is recognized in the seismograms recorded at Nagoya. The first phase P1 is independent of the duration of preliminary tremors (τ), while the second phase P2 is more or less related to it. The times from the commencement of the phase P to each of these phases, P1 and P2 are as follows;
P1=0.46sec, P2=0.053τ+1.417sec.
On the other hand, we can recognize the existence of only one distinct phase in the seismograms recorded at Gifu. The time from P to this phase is independent of the duration of preliminary tremors and
P2=1.48sec.
From these data, the upper crustal structure in Nagoya district was discussed.
