Algorithm for scaling accelerogram (upon upload)

02-Analytical capabilities
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Joined: 09 Jul 2021, 12:49

Algorithm for scaling accelerogram (upon upload)

Post by ftbernales »


I am trying to understand how Seismosoft programs use scale factors in the dialog box when uploading accelerogram/s. My understanding is that the scale factors is literally just a constant multiplier to the time series, hence will just multiply each data point in the earthquake record. And since the accelerogram is then used in solving the ODE for a linear SDOF system, by virtue of linear operations, the resulting response spectra will also be scaled by the same constant multiplier.

However, when I tried to extract the scaled accelerogram after applying a scale factor, and then divided each data point by the corresponding ordinate from the original accelerogram, the multiplier actually varies with no discernable pattern.

What am I missing here? Please correct any misconceptions with the statements I've made above, and please expound on them as well. I really just want to understand how the algorithm works in SeismoMatch/Signal etc.
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Re: Algorithm for scaling accelerogram (upon upload)

Post by seismosoft »

Indeed the scaling factor is applied uniformly in the entire record, hence the spectrum should also be scaled accordingly.
Where did you apply thr scaling factor? When opening the record in the SeismoMatch main screen? Make sure that you have not applied any filtering or baseline correction.
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Re: Algorithm for scaling accelerogram (upon upload)

Post by z.gronti »

Dear ftbernales,

When loading an accelerogram in SeismoMatch and you apply a Scaling Factor in the Input File Parameters window, then all the acceleration values contained in the loaded accelerogram will be multiplied by the assigned scaling factor.

If you select the Save Record THs button and then the Save Data from original Accelerograms checkbox and create the files, you will see that the original accelerogram is multiplied by the specified factor.

In case that you have run the above process as described and you still receive diverged results, please send me your files (original and scaled) to my email ( to check them.
Zoi Gronti
Seismosoft Srl.
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