754 Bulletin of the Seismological Society of America, Vol. 96, No. 2, pp. 754–756, April 2006, doi: 10.1785/0120050148 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 by V. Convertito* and A. Herrero We thank F. O. Strasser, V. Montaldo, J. Douglas, and J. J. Bommer for the interest they have shown in our article (Convertito and Herrero, 2004). Strasser et al. (2006) present a critical comment of our work arguing that the solution proposed by Bommer et al. (2003) is a better solution. Note that the authors are nearly the same in both article and com- ment, except for V. Montaldo. Because this brief article is a reply, we will focus on the arguments directly concerning our article. The main objection supported by Strasser et al. (2006) is that the method we proposed is not appropriate to “style- of-faulting” correction. We completely agree with this as- sertion because it is simply not the scope of our article. We speak about “focal mechanism” intended as radiation pattern and nothing else. This point is clearly stated in the introduc- tion of Convertito and Herrero (2004): “in this article we consider that the focal mechanism influence is only ex- pressed by radiation pattern changes. In particular we do not consider any tectonic influence, stress drop variation or dy- namic effects.” The style-of-faulting parameter, even if its identity is blurred (e.g., Bommer et al., 2003), is an empirical definition of a complex set of physical conditions including the tectonic regime, the medium behavior, rock mechanics, rupture dynamics, and so on. In our opinion, the style of faulting is simply too complex to be used directly in our approach. Because the scope of our article is to show how it is possible to insert inside the main equation of probabi- listic seismic-hazard analysis (PSHA; e.g., Cornell, 1968), simple physical parameters of the seismic source, that is, how it is possible to integrate deterministic parameters inside a probabilistic approach, we have chosen a small target, lim- iting ourselves only to the radiation pattern. We believe that the same approach can be used to insert many other param- eters of the seismic source inside PSHA by using only a theoretical approach such as the fault strike (which has al- ready been shown by Convertito, 2004), the directivity and stress drop. The second important argumentation is that a method *Present address: Istituto Nazionale di Geofisica and Vulcanologia, Os- servatorio, Vesuviano, 80124 Napoli, Italy. based on regression (i.e., Bommer et al., 2003) is better than the method we propose. Once again we agree with Strasser et al. (2006) and this is clearly stated in the conclusion of our article: “when an attenuation law, including a faulting style parameter, is available for a given region, the use of this attenuation law gives a more reliable estimate of the hazard than the one obtained using the corrective coefficient we propose in this article.” Reply to the Focal Mechanism Comment Strasser et al. (2006) start their comment on this topic with the assertion that both methods are identical. This as- sertion is mainly unfounded, in our opinion, simply because our article is not on style of faulting. The misunderstanding comes from a problem of point of view. Strasser et al. (2006) have a phenomenological approach and we have a theoreti- cal point of view. We do not want to reduce the style of faulting or focal mechanism to radiation pattern. We only state that the theory says that a double couple with a partic- ular focal mechanism has a radiation pattern, that is, speak- ing about a theoretical radiation pattern (e.g., Aki and Rich- ards, 1980, p. 115). And this radiation pattern effect can be included in a theoretical way inside the equation of PSHA. It is true that it does not take into account stress drop, di- rectivity, and so on, and it is surely not the response to the whole problem of style of faulting. But it is not its scope, as it was stated in Convertito and Herrero (2004). If the theory, that is, the representation of the seismic source by a double couple, is valid, it is then possible to take into account only for this particular physical effect inside the probabilistic ap- proach. In fact, we believe that the key to improve PSHA is to introduce a priori knowledge, that is, to insert some deter- ministic information into the probabilistic approach. Only in this way will it be possible to reduce the standard deviation, especially within the attenuation law, and to refine the seismic-hazard map. A simple phenomenological approach, that is, based only on the regression approach, is limited because many parameters depend on each other. It is cur- rently difficult to separate their influence, mainly because of