  Seismic vulnerability analysis of existing buildings requires basic
information on their structural behaviour. The ambient vibrations of buildings
and the modal parameters (frequencies, damping ration and modal shapes) that
can be extracted from them naturally include the geometry and quality of
material in the linear elastic part of their behaviour. The aim of this work is
to use this modal information to help the vulnerability assessment. A linear
dynamic modal model based on experimental modal parameters is proposed and the
fragility curve corresponding to the damage state ?Slight? is built using this
model and a simple formula is proposed. This curve is particularly interesting
in moderate seismic areas. This methodology is applied to the Grenoble City
where ambient vibrations have been recorded in 61 buildings of various types
and to the Pointe-\`a-Pitre City with 7 study-buildings. The fragility curves
are developed using the aforementioned methodology. The seismic risk of the
study-buildings is discussed by performing seismic scenarios.
