Dr. Idriss (right) receiving a golden apple from Geotechnical Group treasurer Daniela Bastos at the end of the lecture.

I.M. Idriss is a Professor Emeritus of Civil Engineering at the University of California at Davis. Idriss joined the faculty at UCD following 20 years at Woodward-Clyde Consultants in San Francisco, Santa Ana and Oakland where he was a senior principal. He is the author or co-author of 160 technical papers and research reports on subjects related to the geotechnical aspects of earthquake engineering. His was elected to the US National Academy of Engineering in 1989. He received the first H. Bolton Seed Medal from ASCE in 1995 and the distinguished scholarly public service award from the University of California at Davis in 1999. He was also elected honorary member of the Japanese Geotechnical Society in 2005 and a Distinguished Member of ASCE in 2008. Dr. Idriss is the recipient of the 2010 Ralph Peck Award from ASCE, and the 2010 Arthur Casagrande Memorial Lecture from the Boston Society of Civil Engineers Section (BSCES) of ASCE.

• Why are the published curves of cyclic resistance ration (CRR) versus (N1)60 or versus (N1)60cs different, depending on whose model is implemented?
• Can we treat these differences as "epistemic" uncertainty and hence can use all models with "assigned weights"?
• Can we use site response analyses to obtain the induced cyclic stress ratio (CSR) or do we have to always use the simplified stress ratio equation?
• How should we treat liquefaction at depths exceeding those included in the liquefaction case histories?

Summary and photo by Nidal AbiSaab