In the Spectra Comparisons tab, what algorithm is used to compute "Absolute" and "Relative" differences between record spectra and the target spectrum? My target spectrum has only 20, unequally spaced ordinates, compared to the many more, equally spaced (0.02 sec) ordinates that SeismoSpect computes for my individual records. But even at the matching ordinates, I can't figure out how SeismoSpect is computing the differences. For example, here are the results of comparing Sa for a particular record ("GLFE1FN") to my target Sa at 0.01 second period:
Code: Select all
period GLFE1FN Target Dif1 Dif2 Dif3
0.01 1.251 1.14747464 0.118792725 0.0804 0.0687
Dif1 = abs(Target - GLFE1FN)
Dif2 = "absolute difference" calculated by SeismoSpect
Dif3 = "relative difference" calculated by SeismoSpect
I've tried several different ideas for "Dif1" but I cannot reproduce either Dif2 or Dif3.
Help, please ... [?]