Seismic site response characterisation supported by geostatistical analysis, geomodelling and numerical simulations: Application to seismically active regions of Haiti

Earthquakes constitute one of the most destructive natural hazards, particularly in regions where complex geological settings coincide with high structural vulnerability. Haiti, located along the boundary between the Caribbean and North American plates, has experienced historical damaging earthquakes, and most recently the 12 January 2010 and the 14 August 2021 events. These earthquakes demonstrated that local site effects play an important role in amplifying ground motion and controlling damage patterns, especially in urban areas constructed on soft sediments. The modelling of these effects is therefore essential for improving seismic hazard assessment and risk mitigation strategies in regions potentially exposed to major earthquake impacts.
The present study investigates local seismic amplification through an integrated framework combining geophysical-seismological surveys, geostatistical analysis, 3D geomodelling and numerical modelling in two seismically active regions of Haiti: Anse-à-Veau, near the Enriquillo-Plantain Garden Fault zone, and Cap-Haitien, near the Septentrional Fault zone. These sites were selected due to their geological context and historical seismicity.
In Anse-à-Veau, the study relies on geophysical methods, including ambient noise analysis using horizontal-to-vertical spectral ratios, earthquake recordings processed as standard spectral ratio, multichannel analysis of surface waves, seismic refraction tomography, and electrical resistivity tomography. In Cap-Haitien, the limited geophysical data are completed by borehole with standard penetration test from previous seismic microzonation studies. Geophysical parameters such as fundamental frequency, amplitude, and shear wave velocity are analysed using geostatistical methods, including exploratory data analysis, variogram modelling, kriging and cokriging to generate spatially coherent site characterisation maps.
Three-dimensional geomodels are constructed for the two study areas coupled with geostatistical simulations and implicit modelling techniques to represent the geometry of the superficial deposits overlying the bedrock. These geomodels provide the structural basis for two-dimensional numerical simulations of seismic wave propagation. The modelled site response is compared with measured standard spectral ratios, allowing for the validation of the dynamic models and subsurface geometries.
The results demonstrate that sediment thickness and impedance contrast influence largely the local seismic amplification in the two study areas, locally enhanced by topographic effects. Soft alluvial deposits generate strong low frequency amplification, while colluvial and soft limestone units contribute to minor site effects. The agreement between observed and modelled site responses confirms the robustness of the proposed integrated methodology. This work contributes to seismic microzonation in Haiti and establishes a transferable framework for local seismic hazard assessment in regions characterized by geological complex settings and limited data availability.