Introductory Material
Here we will add web links to material that might help provide an introduction to the theory behind the hazard models in Ergo; however, you may also want to look at the MAE Center website or contact them for more reference material.
Attenuation Relationships
http://srl.geoscienceworld.org/content/68/1/9.full.pdf+html
http://peer.berkeley.edu/course_modules/eqrd/EQDef/sitemo1.htm
Papers
Jong-Wha Bai, Mary Beth D. Hueste, and Paolo Gardoni (2009), "Probabilistic Assessment of Structural Damage due to Earthquakes for Buildings in Mid-America", JOURNAL OF STRUCTURAL ENGINEERING, 10.1061/ASCE0733-94452009135:101155
Ergo Software Algorithm Reference