Cuba

Cuba is the largest island in the Caribbean and experiences moderate seismicity primarily concentrated in its southeastern region, where the island sits astride the transform boundary between the North American Plate to the north and the Caribbean Plate to the south. The Oriente Fault Zone — also known as the Cayman Trough Fault System — runs along the southern coast of Cuba's Oriente (Santiago) province, carrying left-lateral strike-slip motion that accumulates at roughly 2 centimetres per year. This fault is the Cuban expression of the same plate boundary system that produces the Enriquillo-Plantain Garden Fault in Haiti and Dominican Republic. Santiago de Cuba, the island's second city with a long history of earthquake damage, sits directly above the Oriente Fault. The western two-thirds of Cuba, by contrast, are underlain by relatively stable carbonate platform rocks and experience low seismicity. Offshore, the Cayman Trough — a deep transform basin more than 7,000 metres deep — accommodates the bulk of Caribbean-North American relative motion.

The seismic history of Cuba is dominated by the Santiago de Cuba region. The 11 February 1976 Santiago earthquake (magnitude 6.9) caused significant damage to the city's older building stock. Earlier, an 1852 earthquake (estimated magnitude 7.0–7.3) severely damaged Santiago de Cuba and is one of the largest historical events on the Oriente Fault system. The 3 February 1932 Santiago earthquake (magnitude 6.75) also caused extensive damage. In 1766, an earthquake virtually destroyed the town of Bayamo. Cuba experienced a significant magnitude 6.4 earthquake near Santiago in 1947 that damaged hundreds of structures. The eastern tip of Cuba, including Guantánamo Province, experiences the most frequent seismic activity and has a long record of felt events. Western Cuba, including Havana, sits on more stable geological foundations and has no significant historical earthquake record, though distant events from the Caribbean-North American boundary are occasionally felt.

The geological framework of Cuba reflects its complex origin at the margin between the North American and Caribbean plates. The island is not a simple block of continental crust; it is an accreted terrane composed of oceanic plateau material, island-arc volcanics, and sedimentary sequences deformed during the Cretaceous and Paleogene as the Caribbean Plate moved eastward relative to North America. The Sierra Maestra mountains in the southeast expose the oldest and most deformed rocks, while the flat-lying Oligocene and Miocene carbonates that cover most of the island reflect a period of relative tectonic quiescence after the major deformation. The Oriente Fault is a young, active structure superimposed on this older framework, and its seismic coupling suggests it is capable of hosting earthquakes up to approximately magnitude 7.0 to 7.5. [[aftershock]] sequences from Santiago region events tend to be well-recorded by Cuba's national seismological network (CENAIS).