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Comment on "Why Do Modern Probabilistic Seismic-Hazard Analyses Often Lead to Increased Hazard Estimates?" by Julian J. Bommer and Norman A. Abrahamson

Kentucky Geological Survey, 28 Mining and Mineral Resources Building, University of Kentucky, Lexington, Kentucky 40506 zmwang@uky.edu

Mai Zhou

Department of Statistics, 849 Patterson Office Tower, University of Kentucky, Lexington, Kentucky 40506 mai@ms.uky.edu

The first 20% of the full text of this article appears below.

	Introduction

 
In a recent article, "Why Do Modern Probabilistic Seismic-Hazard Analyses Often Lead to Increased Hazard Estimates?," Bommer and Abrahamson (2006) provided an excellent review on probabilistic seismic-hazard analysis (PSHA) and its key issue: how the ground-motion variability is treated. Bommer and Abrahamson (2006) stated that "although several factors may contribute to the higher estimates of seismic hazard in modern studies, the main reason for these increases is that in the earlier studies the ground-motion variability was either completely neglected or treated in a way that artificially reduced its influence on the hazard estimated." In other words, Bommer and Abrahamson (2006) argued that "the main reason for the increases in the modern estimates of seismic hazard is that the ground-motion variability in early application (and indeed formulations) of PSHA was not treated properly," and concluded that "the increased hazard estimates resulting from modern probabilistic studies are entirely appropriate." We argue, however, that ground-motion variability may not be treated correctly in modern PSHA. This incorrect treatment of ground-motion variability perhaps leads to increased hazard estimates, at low annual frequencies of exceedance (10^-4 or lower) in particular.

	Modern PSHA

 
As shown by Bommer and Abrahamson (2006), modern PSHA is often referred to as the Cornell–McGuire method (Cornell, 1968, 1971; McGuire, 1976). According to Cornell (1968), Cornell et al. (1971), and McGuire (1976, 2004), modern PSHA is based on the following equation:

(1)

where is the activity rate, f_M(m) and f_R(r) are the probability density function (PDF) of earthquake magnitude M and epicentral or focal distance R, respectively, and y_mr and _ln,y are the median and standard deviation at m and r. f_M(m) and f_R(r) were introduced to account . . . [Full Text of this Article]

	Concluding Remarks

 

Related articles in Bulletin of the Seismological Society of America:

Why Do Modern Probabilistic Seismic-Hazard Analyses Often Lead to Increased Hazard Estimates?

Julian J. Bommer and Norman A. Abrahamson
Bulletin of the Seismological Society of America 2006 96: 1967-1977. [Abstract] [Full Text]  

Reply to "Comment on ‘Why Do Modern Probabilistic Seismic-Hazard Analyses Often Lead to Increased Hazard Estimates?’ by Julian J. Bommer and Norman A. Abrahamson" by Zhenming Wang and Mai Zhou

Julian J. Bommer and Norman A. Abrahamson
Bulletin of the Seismological Society of America 2007 97: 2215-2217. [Extract] [Full Text]  

This article has been cited by other articles:

				J. J. Bommer and N. A. Abrahamson Reply to "Comment on 'Why Do Modern Probabilistic Seismic-Hazard Analyses Often Lead to Increased Hazard Estimates?' by Julian J. Bommer and Norman A. Abrahamson" by Zhenming Wang and Mai Zhou Bulletin of the Seismological Society of America, December 1, 2007; 97(6): 2215 - 2217. [Full Text] [PDF]