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Comment on "Influence of Focal Mechanism in Probabilistic Seismic Hazard Analysis" by Vincenzo Convertito and André Herrero

¹ Department of Civil & Environmental Engineering
Imperial College London
London SW7 2AZ, United Kingdom
fleur.strasser@imperial.ac.uk
 (F.O.S., J.J.B.)
² Istituto Nazionale di Geofisica e Vulcanologia
Via Bassini 15, 20133 Milano, Italy
 (V.M.)
³ BRGM, ARN/RIS
3 avenue C. Guillemin, BP 6009
45060 Orleans Cedex 2, France
 (J.D.)

The first 300 words of the full text of this article appear below.

	Introduction

 
The influence of style-of-faulting on strong ground motions has been the subject of debate for some time. Although some controversy persists, the general consensus is that ground motions produced by reverse faults are higher than those produced by normal faults, whereas motions from strike-slip faults are somewhere in between. In a recent article, Convertito and Herrero (2004) derived a correction factor for focal mechanism to be applied to predictive equations. This issue was previously addressed by Bommer et al. (2003). Although this article is cited by Convertito and Herrero, it seems that its aims and scope were not well understood, and we would therefore like to clarify what the method presented therein entails, especially because we feel that Convertito and Herrero's approach of characterizing focal mechanisms based solely on the radiation pattern is difficult to justify.

After presenting their correction scheme, Convertito and Herrero go on to present an implementation of probabilistic seismic hazard analysis (PSHA) explicitly accounting for focal mechanism. This represents a real innovation in terms of methodology because it allows propagation of the improvements in ground-motion prediction gained through the focal-mechanism adjustments to hazard estimation. Characterizing the dominant scenario in terms of focal mechanism furthermore has the advantage of providing constraints for numerical simulations that are derived directly from the hazard computation, rather than from arbitrary assumptions. However, in our opinion, the methodology presented by Convertito and Herrero has some serious shortcomings which would need to be addressed before it can lead to improvements of the PSHA methodology. Our discussion includes a comparison with the new Italian seismic hazard map, which was derived using the Bommer et al. (2003) adjustment methodology.

	Focal Mechanism in Ground-Motion Prediction

 
In the first part of their article, Convertito and Herrero derive a correction factor for focal mechanism to . . . [Full Text of this Article]

	Incorporation of Focal Mechanism in PSHA

 

	Conclusions

 

Related articles in Bulletin of the Seismological Society of America:

Influence of Focal Mechanism in Probabilistic Seismic Hazard Analysis

Vincenzo Convertito and André Herrero
Bulletin of the Seismological Society of America 2004 94: 2124-2136. [Abstract] [Full Text]  

This article has been cited by other articles:

				V. Convertito and A. Herrero Reply to "Comment on 'Influence of Focal Mechanism in Probabilistic Seismic Hazard Analysis' by Vincenzo Convertito and Andre Herrero," by F. O. Strasser, V. Montaldo, J. Douglas, and J. J. Bommer Bulletin of the Seismological Society of America, April 1, 2006; 96(2): 754 - 756. [Full Text] [PDF]