Seismic Microzonation

Abstract. Pointe-à-Pitre, the main city of Guadeloupe in the FrenchWest Indies, has on several occasions
been partially destroyed by major historical earthquakes. Moreover, a post-seismic assessment
of the damage from the 1985 Montserrat earthquake indicates that the town is prone to site effects.
Consequently, from 1996 to 1998, BRGM conducted a seismic microzonation study based on geotechnical
and geological data. At the same time, three seismological studies were being conducted –
two based on earthquake recordings using a time-series analysis and the classical spectral ratio (CSR)
method (CETE/LCPC and BRGM), and the third based on noise measurement at 400 points using the
horizontal-to-vertical noise ratio (HVNR)method (CETE/LCPC). The objective of this paper is not to
carry out a new microzonation study by taking into account all the results, but rather to show in what
respects the results of these different methods are in agreement or not. A comparison of the results
of the seismological studies with the geotechnical microzonation shows that they are in fairly good
agreement, albeit with some discrepancies. The results indicate that the seismological methods and
the geotechnical data are highly complementary and should be used together in compiling seismic
transfer-function microzonation maps