I am making manual load combination and I got struck in calculating Mapped spectral response acceleration Ss in order to calculate vertical component of earthquake Ev=0.2SdsD we have to calculate Sds which is equal to Sds=2/3Sms . and Sms=FaSs now according to section 11.4.1 of ASCE 7-05 it says in order to calculate Ss see figure 22-1 through 22-14 but these figures are maps and they are for US so how to calculte this parameter or whats the alternative for this problem to calculate vertical com