Haiti

Haiti occupies the western third of Hispaniola, straddling one of the Caribbean's most dangerous seismic corridors. The island lies along the transpressional boundary between the Caribbean Plate to the south and the North American Plate to the north, creating a tectonic environment where compressional and strike-slip forces combine in complex [[fault]] systems. Two major left-lateral strike-slip fault systems dominate the hazard: the Septentrional Fault, which runs along the northern coast, and the Enriquillo-Plantain Garden Fault Zone (EPGFZ), which crosses the southern peninsula through densely populated lowlands. Both faults move at rates of roughly 6 to 8 millimetres per year, accumulating elastic strain that eventually releases in destructive earthquakes. Offshore, oblique convergence creates additional thrust hazard along segments of the Caribbean-North American plate boundary. The combination of active faulting, densely populated urban centres built on soft alluvial deposits, widespread unreinforced masonry construction, and acute poverty creates one of the highest concentrations of earthquake risk anywhere in the Western Hemisphere.

The seismic history of Haiti includes one of the deadliest earthquakes in recorded history. On 12 January 2010, a magnitude 7.0 earthquake struck 25 kilometres southwest of Port-au-Prince, directly rupturing along the EPGFZ. The [[epicenter]] was shallow — roughly 13 kilometres deep — maximising energy delivery to the surface. Official estimates placed the death toll between 100,000 and 316,000 people; over one million were displaced and 250,000 residential and 30,000 commercial buildings were either destroyed or severely damaged. The catastrophic death toll reflected decades of unregulated construction, near-total absence of [[fault]] setback zones, and a healthcare infrastructure that was itself destroyed in the shaking. Three years of [[aftershock]] activity followed. Haiti had experienced major historical seismicity before: a 1770 earthquake near Léogâne destroyed the settlement; an 1842 event (estimated magnitude 8.1) struck the northern peninsula and killed an estimated 5,000 people in Cap-Haïtien. In August 2021, a magnitude 7.2 earthquake struck the Nippes department on the southern peninsula, killing 2,248 people and injuring over 12,000, demonstrating that the hazard remained undiminished more than a decade after 2010.

Haiti's vulnerability is inseparable from its geological setting. The island of Hispaniola formed as the Caribbean Plate migrated eastward relative to the North American Plate, dragging a mosaic of oceanic and island-arc material along transpressional fault systems. The Enriquillo-Plantain Garden Fault is analogous in some respects to the San Andreas Fault — a long strike-slip structure capable of hosting very large earthquakes — but unlike the San Andreas, it runs through one of the most densely and precariously populated corridors in the Western Hemisphere. The [[intensity]] maps produced after the 2010 earthquake showed that soft alluvial soils in the Port-au-Prince basin amplified [[seismic-wave]]s significantly, causing buildings on the worst soils to experience shaking far more severe than those on nearby bedrock. International geologists and engineers have since worked to produce probabilistic seismic hazard maps that could guide future construction, but implementation has proceeded slowly amid continuing political instability and economic constraints.