The method of estimating of the most probable and maximum possible displacements that can take place in the structure foundation crossed by seismogenerating fault, if the earthquake of expected magnitude will occur, is proposed. Besides, the method of the adopted displacement occurrence probability estimation is under review. Taking into consideration the changeability of displacement values along the seismic surface rupture traces, just these parameters could be used for the design purpose. Estimations are based on the analysis of surface rupture parameters of more than 230 earthquakes.
Est proposee une methode d'estimation des valeurs les plus probables et limites des deplacements sismiques possibles suivant les ruptures dans la fondation des ouvrages en fonction de la magnitude du tremblement de terre prevu. En plus, est envisage le moyen à l'aide duquel on determine les probabilites de la naissance des deplacements sismiques. Compte tenu des variations des valeurs de deplacements suivant les traces des ruptures sismiques actuelles, ce sont justement ces paramètres qu'on propose à utiliser dans les etudes. L'estimation est basee sur l'analyse des paramètres des ruptures sismiques formees pendant plus de 230 tremblements de terre.
Die Methode der Bewertung der wahrscheinlichsten und möglichsten seismischen Brueche die können in der Bauwerkgruendungen stattfinden gemaβ der erwarteten Starke des Erdhebens ist beantragt. AuBerdem, das Verfahren, die Warscheinlichkeit seiner Entstehung zu festsetzen ist betrachtet. Mit Ruecksicht auf der Unbestandigkeit der Bruchgröβen entlang gegenwartige seismische Trassen, gerade diese Parameter können fuer Projektierung ausgeneizt werden. Die Bewertangen sind auf der Analyse der seismischen Brueche der mehr als 230 Erdheben begruendet.
Surface faulting is one of the most dangerous phenomena connected with earthquakes. The strong earthquakes may be accompanied by surface ruptures dozens and hundreds kilometers long with the displacements up to 5–10, sometimes 12–14 metres. In practice the possible displacement estimation is of the most importance for a long hydrotechnical or transport tunnels design, since it is often impossible, while choosing their alignments, not to cross any seimogenerating fault. Such estimation may be based either on the specific fault that cross the structure detailed investigations, or on the recent seismic surface ruptures analysis. The former way needs to perform a lot of field studies and in many cases cannot ensure sufficiently well-founded estimates. Indeed, even in the seismogenerating fault zones investigated in a most extent such as San Andreas (Ziony & Yerkes 1985) or Anatolian (Ambraseys 1970) a number of well-known seismic ruptures is relatively small, so that displacement prediction based on the statistical analysis of only the local data would not be reliable enough. It would be difficult to substantiate, in particular, that any future displacement cannot exceed the maximum value, recorded in the studied fault zone. Therefore I consider that in the majority of seismically active regions, especially on the initial design stages, more well-founded estimates would be based on the worldwide seismic surface ruptures data analysis.
The characteristic feature of seismic surface ruptures is the changeability of displacement along the fault trace (Fig. 1). It may depend on the peculiarity of source rupturing, on the fault section orientation and may be also connected with secondary effects such as vertical displacement increasing while fault cross the local ridges or the displacement inconstancy due to local soil conditions. I think that in the majority of cases it will be impossible to predict unequivocally neither the displacement value at the site nor its mutability along the expected surface rupture and therefore the probabilistic approach should be used. All regressions of displacement on earthquake size that I know (Iida 1965; Chinnery 1969; Slemmons 1982; Shteinberg 1983; Bonilla et al. 1984; Nowroozi 1985) are based on the analysis of maximum displacements recorded for the every surface rupture analysed.