Guralp-systems ART Manuel d'utilisateur télécharger pdf (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

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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Guralp-systems ART Manuel d'utilisateur Page 19

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