The 1708 Manosque seismic sequence (France): a multidisciplinary approach and application of the EMS.
G. Quenet (1), A. Levret (2), O. Scotti (3), D. Baumont (3), and G. Poursoulis (4)
Symposium SCA-1 - XXVIII General Assembly of the European Seismological Commission - Gênes, Italie -
1-6 septembre 2002
The seismic sequence of 1708 lasted from March through October and produced a series of events that caused damage in many villages along thé Durance fault, France. Two main events have so far been identified in the historical record, one on the 21st of March and the other on the 14th of August. By distinguishing primary and secondary sources and replacing them in their socio-economic-historical context we could define the extension of the damaged area for both events.
Among the primary sources a precious and very complete document was found which gave us thé opportunity to apply the EMS scale on an old event. This document written by bricklayers seven months after the catastrophe, reports on the damage caused by the earthquake in the city of Manosque. The descriptions concern 740 buildings but one of the difficulties in the application of the new EMS scale is the attribution of a vulnerability class to each building. Based on economical and social criteria highlighted by the historical context, four neighbourhoods were identified. A statistical analysis established on various criteria, such as the degree of damage with respect to the EMS98 scale, the cost of repairs, and different assumptions on the vulnerability classes leads to the estimation of an intensity range. A test is made with the MSK scale currently used until now.
We believe that the multidisciplinary approach that has already produced exciting results in Italy, must be encouraged in France as well. The uncertainties in the evaluation of the intensities of poorly documented earthquakes can be greatly reduced by a thorough historical analysis of the sources. Architectural disorders can be observed today on twelve old buildings (1% of the total damaged buildings) and their analysis is in progress. This should allow validation of the interprétation of the historical documents.
(1) CNRS, Institut d'Histoire Moderne et Contemporaine, 45, rue d'Ulm, 75005 Paris. France
(2) Groupe APS, Site de Ruscino, Château-Roussillon, F-66 000 Perpignan, France
(3) IRSN/DPRE/SERGDBERSSIN - BP 17 92262 Fontenay-aux-Roses. France
(4) CNRS, Maison de l'Orient Méditerranéen, 7, rue Raulin, 69007 Lyon. France.