Seismic Microzoning of Cap-Haïtien: Effects of Lithological Site and Liquefaction

After the earthquake of January 12, 2010 in Haiti, the Haitian Government has resolved to implement a program of seismic microzonation for most vulnerable cities in the country by the way of prevention. Metropolitan Port-au-Prince and five cities in the North of Haiti including Cap-Haitien were included in this program.

The seismic microzonation is an important tool for the knowledge of the seismic risk. It is based on the collection of geological, geophysical and geotechnical data. It describes a specific class of soil associated with each type of soil. Its goal is to map the homogenous zones of soil to effects of site lithology, topographic site effects, liquefaction and ground movements.

This work is based on two aspects of the studies of microzoning for the city of Cap-Haïtien: effects of lithological site and Liquefaction.

The zoning of site effects is to identify and map the areas with consistent geological and geomechanical characteristics and homogeneous seismic response; the objective is to provide, in each zone, seismic movements adapted.

Five classes of soil at site effects were distinguished. Associated responses spectra were obtained by a 1D nonlinear analysis using CyberQuake software (Modaressi et al. 1997 BRGM).

The zoning of the liquefaction present the liquefaction potential of different areas. Three levels of risk of liquefaction were found during this study that a large part of the city is strongly liquefiable.