Help how to calculate response spectrum (Ss and S1 ) from PGA (2%PE 20Gal and 10% PE 10 Gal) Country is Kuwait (out side the US, can't use USGS software out the limits)
Ss & S1 are based upon the PGA for a 2% in 50 year (2475 year return) event and 5% damping. Check this document "UFC 3-310-01 Structural loads.pdf" for a published Ss and S1, it has many cities where US bases are throughout the world.