Earthquakes are one of the most lethal natural risks and those which cause most damage. From 1994 to 2004, earthquakes resulted in over 200,000 casualties throughout the world. While the earthquake mechanism is now better understood, in terms of its origin and propagation, it remains an unpredictable phenomenon.
Not all populations are equal faced with this danger. For an equivalent magnitude, an earthquake will be less destructive in a well-prepared country where earthquake-resistant construction is integrated into the culture than in an underprivileged or overly lax country, where best practices are not complied with. Prevention is structured around three aspects: knowledge of the regional earthquake risk, via the study of past earthquakes, structural adaptation to probable seismic motions and preparation of the populations and emergency services. The law of 22 July 1987 (article 125-2 of the environmental code) instituted the citizens’ right to information on the major risks to which they are subjected over all or part of the territory. Several compulsory documents (DDRM, DICRIM etc.) are therefore designed to inform everyone of the risks to which they are exposed and the safety instructions to be complied with “before, during and after” the phenomenon.
Issuing preventative information and applying compulsory earthquake-resistant construction rules does not however mean that industrialized countries are safe, as the 1995 Kobe earthquake in Japan illustrated (6,000 dead). The main property of earthquake-resistant structures is not to protect at all cost but to limit the damage.
Our territory, like many others, is exposed to the earthquake risk. In the past, France has been hit by major earthquakes (Lambesc in 1909, 46 dead; Pointe-à-Pitre in 1803 and 1839, several hundreds to thousands dead etc.) and others will occur in the future: this is a certainty. This occurrence in mainland France or the French Antilles will result in numerous casualties as well as economic damage which will amount to several billion or tens of billion Euros.
According to the environmental code (articles R. 563-1 to R.563-8), there are two types of structures, “normal risk ” and “special risk ” structures, referring to a specific earthquake-resistant regulation depending on one or other of these categories. Amongst “special risk” structures, some classified installations for environmental protection (CIEP) would be likely to generate a large number of casualties and durable economic consequences for the country. It should be reminded that any industrial or agricultural operation likely to create risks or cause pollution or nuisance, notably in terms of residents’ health and safety, can be defined as a classified installation. In case of an earthquake, these facilities are more sensitive than others because their damage can affect a sizeable population.
The installations built using earthquake-resistant construction rules are less exposed to the risks. Scientifically validated methodological approaches have been developed to provide designers with earthquake-resistant construction rules with regard to “normal risk” structures such as collective dwellings, individual houses or public buildings, as well as “special risk” structures.
In 1969, the first earthquake-resistant construction rules were put in place for large-scale buildings. These rules, known as PS 69, were reviewed and altered in 1982. Subsequently, under the impetus of the French Association for earthquake engineering created in 1984, they were modified once again in 1992 (so-called PS92 rules). These provisions will now be progressively replaced by European rules known as “Eurocode 8”.
According to the circular of 27 May 1994 relative to the order of 10 May 1993, so-called “special risk” installations in the sense of article 6 of the decree of 14 May 1991 include, among other things, the classified installations defined in article 1 of the order of 10 May 1993 . For these installations, earthquake risk prevention must be subject to a case-by-case study. The examination of the earthquake risk relative to a classified installation is part of the risk assessment, in the same capacity as that of other natural risks. The order initially defines a method to assess the earthquake hazard to be taken into account, after which it stipulates the listing of installations or equipment which must be subject to protection measures, and the safety objectives with which these protection measures must comply.
Article 41 of the law of 22 July 1987 relative to civil safety organisation;
Decree of 14 May 1991 relative to earthquake risk prevention;
Order of 10 May 1993 stipulating earthquake-resistant rules applicable to the installations subject to the legislation on classified installations;
DPPR/SEI circular of 27 May 1994 relative to the order of 10 May 1993 stipulating earthquake-resistant rules applicable to classified installations for environmental protection;
Circular no. 2000-77 of 31 October 2000 relative to the technical monitoring of structures for the prevention of earthquake risks.
 Structures for which the consequences of an earthquake remain contained to their occupants and immediate vicinity (classified into 4 categories)
 Structures for which the impact on people, assets and the environment of minor damage caused by an earthquake can exceed the immediate vicinity of these structures
 stipulating the earthquake-resistant rules applicable to classified installations and specifying, amongst other things, the reference seismic motions to be taken into account