The UHT has an option to change the period, so I wouldnt have thought the difference came from there. Regardless, being geotech I'm usually only looking for PGAs. Like you say, different load factors, or maybe general conservative(ness?) during model development might be the reason. Perhaps with...
I'm curious why the unified hazard tool PGAs I'm getting are 0.05g smaller than those from AASHTO or my state seismic tool. There really is no good explanation on the USGS, except to say that they are different so you shouldn't use the UHT... Anyone have an idea why? Are they disregarding some...
