Corrected Record

In a Corrected Record the disturbances present in the original signal at both high and low frequency have been removed or reduced (see Uncorrected Record).

Two subsequent steps are employed in order to correct the low frequency disturbances:

- the baseline is removed in the time domain (see Baseline Correction)

- the accelerogram is high-pass filtered (see Filter Correction)

In order to correct the errors at high frequencies, the accelerogram is low-pass filtered (see Filter Correction)

The following procedure has been considered in the processing of ITACA accelerometric data:

- baseline correction (removal of the signal average value);

- application of a cosine taper, with an extension based on a visual inspection of the record (typically between 2% and 5% of the signal total length); The taper is not applied to those records identified as late-triggered (see Triggered Record);

- visual inspection of the Fourier Spectrum, to select the band-pass filter frequency range. When possible, the same frequency range is selected for the three components;

- application of a acausal Butterworth filter of the second order, in the frequency range selected at the previous point;

- double integration of the acceleration to obtain the displacement time history;

- removal of the linear drift present in the displacement time history;

- double derivation to obtain the corrected acceleration, which is compatible with the corrected displacement.