Long-period transition period, TL, for the conterminous United States, Alaska, Hawaii, Puerto Rico and United States Virgin Islands, 2009 NEHRP.
For designing buildings and other structures to safely resist earthquakes, the 2009 NEHRP Recommended Seismic Provisions and the 2010 ASCE/SEI 7 Standard contain maps of long-period transition periods, TL.  TL is based on the modal moment magnitude obtained from the disaggregation of a 2% probability of exceedance in …