“The State of the Practice of Seismic Hazard Analysis: From the Good to the Bad”

Norman A. Abrahamson wins EERI's 2009 Distinguished Lecture Award

• Download PowerPoint presentation [6.2Mb].

Norman A. Abrahamson, a senior engineering seismologist in the Geosciences Department at Pacific Gas and Electric Company in San Francisco, delivered the 2009 Distinguished Lecture for the first time on February 12 during the Annual Meeting.

Abrahamson reviewed the state of the practice of seismic hazard analysis and development of design time histories. He observed that the practice of seismic hazard analysis varies tremendously from poor to very good. The large variability in practice is not simply a reflection of project budgets, as a large variation exists for similar scale projects. Although the basic methodology for seismic hazard analysis has been well established, there remains widespread misunderstanding of the basic concepts that contribute to poor practice. Abrahamson described some of the most common misunderstandings and common aspects of bad practice, and summarized the aspects of good practice that should be expected for low-end and high-end studies. 

For the development of design time histories, Abrahamson indicated that the state of practice is more variable than for seismic hazard analysis. Key aspects such as how representative time histories are selected and how they are modified (by scaling or by spectral matching) vary tremendously based on the opinions of the project participants or reviewers. In most cases, these opinions are based on “comfort” level rather than objective technical criteria. Abrahamson showed examples that illustrate the large range of quality of current practice. He stated that the state of practice for developing time histories will not improve until objective quantitative criteria are developed to judge the appropriateness of the non-stationary aspects of the proposed time histories for the particular project.

For background information about Abrahamson, see page 1 of the January 2009 Newsletter. Groups who wish to invite him to present the lecture should This e-mail address is being protected from spambots. You need JavaScript enabled to view it .