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Sensors 2008, 8
displacement. PGA, PGV, and PGD are the peak values of the three components. In real-time
operation, velocities and displacements are recursively filtered with a one-way Butterworth high-pass
filter with a cutoff frequency of 0.075 Hz for removing the low frequency drift during the first
integration process.
400
200
0
-200
20
10
0
-10
-20
8
4
0
0.5 cm
-4
-8
-12
-3
Figure 1. Vertical component acceleration, velocity and displacement seismograms for the 2007
Niigata Chuetsu-Oki earthquake, at the nearest stations, NIG018 (∆=14 km). A ground-motion period
parameter τ
and a high-pass filtered displacement amplitude parameter P
c
τ
c
Pd
Pd threshold warning
0
3
6
Time after P arrival (second)
initial 3 sec of the P waveforms.
M
6.6, focal depth 10 km
PGA
w
Knet Station NIG018
Epicentral distance 14 km
PGV
PGD
9
12
15
18
are determined from the
d
3
21
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