Guralp Systems ART - Manual (Page 19)

User guide
lower limit is 0.1s;
37. period used as upper limit in calculation of acceleration
spectral intensity (‘ASI limits Upper’). A commonly used
upper limit is 0.5s.
38. the material to assume for the computation of the drift
spectra (steel, R/C or other)
Clicking on the ‘Save’ button saves the chosen parameters to a
file called art_default.dat which is loaded each time ART is
used. The parameters are not automatically saved when the
window is close using the close icon; however, they are used
for the rest of the session.
3.2.3 Interactive selection of filter parameters
The Order and corner frequency fl of the Butterworth filter, as
well as the Length of pre-event time, can be set interactively.
1. Select a single stream in the centre panel of the main
window. Click Options.
2. In the Options window, beneath the legend Length of
pre-event time, click the Select button. A window will
pop up displaying the stream you have selected.
3. The top two graphs show the acceleration and
displacement time histories for the selected stream, with
the current low-pass filter applied.
4. The red line shows the current Length of pre-event time
setting. Data before the line is used to calculate spectra
of ambient ground motion; data after it is treated as part
of the event.
Click in either graph to move the line. The spectra below
are updated automatically.
5. The plot at bottom left shows the Fourier amplitude
spectrum of ambient ground motion (in blue) and of the
event (in black), using the current filter settings.
The plot at bottom right shows the ratio between the two
spectra (
i.e. the signal-to-noise ratio). The horizontal red
lines represent signal-to-noise ratios of 2:1 and 1:2; the
blue lines represent ratios of 3:1 and 1:3.
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