The function generates:
- pseudo-spectral acceleration (PSA)
- pseudo-spectral velocity (PSV)
- spectral displacement (SD) spectra for given damping ratio (xi).
Spectral ordinates are for linear-elastic single-degree-of-freedom system with unit mass.
Reference: Wang, L.J. (1996). Processing of near-field earthquake accelerograms: Pasadena, California Institute of Technology.
This code is converted from Matlab code of Dr. Erol Kalkan, P.E. Link
An example can be seen by running demo.py