Caribbean Earthquake Risk: Islands on the Plate Boundary

At 4:53 PM on June 7, 1692, the ground beneath Port Royal, Jamaica shook violently for approximately two minutes. Port Royal was then the largest and wealthiest city in the English Americas — a city of merchants, pirates, and traders built on a long spit of sand that extended into Kingston Harbour. The earthquake triggered the liquefaction of the sandy sediment beneath the city, and a large portion of Port Royal — buildings, streets, fortifications, and thousands of people — slid into the harbour and sank beneath the water. An estimated 2,000 people died in the immediate event, and another 3,000 died in the subsequent weeks from injuries and disease. Port Royal never fully recovered; it was subsequently surpassed by Kingston, built on more stable ground across the harbour, as the island's commercial center. The sunken ruins of Port Royal remain on the floor of Kingston Harbour today — the Caribbean's own Atlantis, preserved by the anaerobic conditions of the shallow bay, and one of the best-preserved examples of 17th-century urban archaeology anywhere in the world.

The 1692 Port Royal disaster is the Caribbean's defining earthquake event — the one that established in the historical record that these beautiful, tropical islands sit in one of the world's most seismically active regions. But it is far from the only example. The 2010 Haiti earthquake killed approximately 160,000 people — the deadliest earthquake of the 21st century — and struck a country whose poverty, building stock vulnerability, and governance challenges amplified a geologically moderate event into one of the worst natural disasters in the history of the Western Hemisphere. Puerto Rico experienced a M6.4 earthquake in January 2020 that damaged approximately 8,000 homes, caused 1 death, and left tens of thousands without power for weeks. The Lesser Antilles island arc — the curving chain of islands from Trinidad northward to the Virgin Islands — sits directly atop the subduction zone where the North American plate descends beneath the Caribbean plate, and has produced multiple M7–8 events in the historical record with tsunamis that swept coastal communities across the basin.

For millions of people living in the Caribbean — on islands that range from small sovereign nations of a few hundred thousand people to the 11 million of Cuba, the 10 million of Haiti and the Dominican Republic — earthquake risk is not an abstraction. It is a lived reality of occasional felt earthquakes, a historical record full of disasters, and a preparedness challenge that small island developing states face with limited resources, limited engineering capacity, and the additional burden of being simultaneously vulnerable to hurricanes, volcanic eruptions, and tsunamis from any direction.

The Caribbean Plate: A Small Plate with Big Hazards

The Caribbean plate is one of the smaller tectonic plates — roughly 3.2 million km² in area, compared to the Pacific plate at 103 million km². It occupies the basin of the Caribbean Sea and is surrounded on almost all sides by much larger plates moving against it: the North American plate to the north and east, the South American plate to the south, and the Cocos and Nazca plates subducting beneath Central America and northwestern South America to the west. The Caribbean plate itself moves eastward relative to the North and South American plates at approximately 2–3 cm per year — a slow relative motion, but one that generates major earthquakes along a complex system of plate boundaries that encircle the basin.

The boundaries of the Caribbean plate take several distinct forms, each generating its own characteristic seismicity. To the east, the North American plate subducts beneath the Caribbean plate along the Lesser Antilles subduction zone — the volcanic island arc extending from Trinidad northward to the Virgin Islands. To the north, the Caribbean-North American boundary is dominantly strike-slip — a system of left-lateral faults including the Septentrional fault in Hispaniola and the Oriente fault south of Cuba — with significant tectonic complexity in the Hispaniola-Puerto Rico region where elements of both compression and extension coexist. To the south, the Caribbean-South American boundary is similarly complex, with oblique convergence producing transpressional tectonics throughout Trinidad, Venezuela, and Colombia.

The Lesser Antilles Subduction Zone: Eastern Caribbean Volcanic Arc

The eastern margin of the Caribbean is defined by the Lesser Antilles subduction zone — the convergent boundary where the ancient Atlantic portion of the North American plate descends westward beneath the Caribbean plate at approximately 2 cm per year. The subduction generates the volcanic arc of the Lesser Antilles — the curving chain of islands from Grenada in the south through St. Vincent, St. Lucia, Martinique, Dominica, Guadeloupe, Montserrat, Antigua, and the Virgin Islands to the north. These islands are the volcanic expression of the subduction process — their peaks are volcanoes fed by fluids released from the subducting slab, producing the same type of explosive arc volcanism that characterizes subduction zones worldwide.

The Lesser Antilles subduction zone is also capable of generating large megathrust earthquakes on the interface between the Atlantic crust and the Caribbean plate. The Barbados Ridge — an accretionary prism building up at the trench — indicates that significant sediment is being subducted or accreted, and historical records document major tsunamigenic earthquakes in the Lesser Antilles that are consistent with megathrust events. The 1843 M8.0 Guadeloupe earthquake — which killed approximately 3,000 people and generated a tsunami felt throughout the eastern Caribbean — is the most clearly documented large megathrust event in the Lesser Antilles record. The 1755 Lisbon earthquake tsunami, which crossed the Atlantic and caused waves throughout the Caribbean, demonstrated that the region is also exposed to far-field tsunamis from the eastern Atlantic.

The Volcanic Hazard Intersection

In the Lesser Antilles, earthquake and volcanic hazard are inseparable. Every island in the arc hosts active or potentially active volcanic systems — Soufrière Hills on Montserrat erupted continuously from 1995 to 2010, destroying Plymouth (the island's capital city) and forcing the evacuation of most of the island's population. La Soufrière on St. Vincent erupted in April 2021, requiring the evacuation of 16,000 people from the northern part of the island. Montagne Pelée on Martinique is one of the world's most dangerous volcanoes — its 1902 eruption killed 29,000 people in what remains the deadliest volcanic disaster of the 20th century. Each of these volcanic systems produces seismicity — volcanic tremor, LP earthquakes, and dike intrusion swarms — that is distinct from but superimposed on the tectonic seismicity of the subduction zone, creating a complex monitoring challenge for the limited resources of small island seismic networks.

Haiti and the Enriquillo-Plantain Garden Fault System

No earthquake in the Caribbean's modern history has had the humanitarian impact of the January 12, 2010 Haiti earthquake. The M7.0 event struck at 4:53 PM local time — when schools, markets, offices, and homes were all occupied — with an epicenter 25 km west of Port-au-Prince, the capital city of 3 million people. The earthquake lasted approximately 35 seconds. In that time, an estimated 250,000 buildings were damaged or destroyed, including the Presidential Palace, the Parliament building, the headquarters of the UN mission in Haiti, and hundreds of thousands of residential structures. Approximately 160,000 people were killed — a death toll that represents the deadliest earthquake of the 21st century by a substantial margin and one of the deadliest in Western Hemisphere history.

The Enriquillo-Plantain Garden Fault

The 2010 earthquake ruptured the Enriquillo-Plantain Garden Fault (EPGF) — a left-lateral strike-slip fault running east-west along the southern peninsula of Haiti and into Jamaica to the west. The EPGF is part of the broader left-lateral fault system that accommodates the northward motion of the Caribbean plate relative to the North American plate in the Hispaniola region — a transpressional zone where the oblique convergence between the two plates is partitioned between thrust motion on north-dipping reverse faults and left-lateral motion on the EPGF and related structures.

Paleoseismic studies of the EPGF indicate that the 2010 rupture represented only a partial release of the elastic strain accumulated on the fault — the rupture was approximately 60 km long, while the total fault system extends for several hundred kilometers across Hispaniola and into Jamaica. The portion of the fault west of the 2010 rupture — in western Haiti near the Tiburon Peninsula — and the eastern portion in the Dominican Republic are both assessed as having accumulated significant slip deficits that were not released in the 2010 event. Coulomb stress modeling indicates that the 2010 rupture increased stress on adjacent fault segments, potentially advancing the timing of future earthquakes on those segments.

Why Haiti Suffered So Catastrophically

The question of why the 2010 Haiti earthquake killed 160,000 people while the 2010 Chile M8.8 — released roughly 500 times more energy — killed approximately 550 is the starkest illustration in the series of the principle that earthquake magnitude alone does not determine casualties. In Haiti's case, five factors converged to produce the catastrophic outcome:

• The earthquake was shallow (13 km depth) and the epicenter was in the near-field of the most densely populated area of the country — there was no distance to attenuate the shaking before it reached Port-au-Prince
• The building stock of Port-au-Prince was dominated by unreinforced masonry and concrete buildings constructed without seismic provisions or engineering oversight — a pattern reflecting decades of poverty, informal settlement growth, and essentially non-existent building code enforcement
• Port-au-Prince is built partly on soft alluvial and fill soils in the low-lying areas that amplified ground motion significantly relative to bedrock sites — particularly in the densely built informal settlements of the lower city
• Haiti's emergency response capacity was negligible — the earthquake destroyed the main government buildings including the health ministry, the police headquarters, and many hospitals, leaving virtually no functional governmental emergency response infrastructure at the moment when it was needed most
• The timing — 4:53 PM — meant that most buildings were near full occupancy when they collapsed, maximizing the toll from structural failure

Puerto Rico: The Muertos Trough and the 2020 Earthquake

Puerto Rico occupies a tectonic position of unusual complexity at the junction between the Caribbean plate and the North American plate — specifically at the transition between the east-west Caribbean-North American transform boundary and the north-south Lesser Antilles subduction system. The island sits on a microplate within this boundary zone that is being compressed from multiple directions, with the Puerto Rico Trench — the deepest point in the Atlantic Ocean at 8,376 meters — lying just north of the island where the North American plate descends beneath the Caribbean.

The Fault Systems Around Puerto Rico

Puerto Rico is surrounded by active fault systems on virtually every side. To the north, the Puerto Rico Trench subduction zone and the associated thrust and normal faults represent the highest-magnitude hazard source — capable of generating M8+ megathrust earthquakes and potentially large tsunamis on the north coast. To the south, the Muertos Trough is a zone of south-dipping thrust faults where the Caribbean plate is being subducted southward beneath a microplate in a reverse subduction geometry — the opposite polarity from the northern trench. To the west, a series of normal faults and the Mona Rift separate Puerto Rico from Hispaniola. This convergence of active structures on a compact island of 3.3 million people creates a hazard exposure that Puerto Rico's seismic history has repeatedly confirmed.

The 2020 Southwestern Puerto Rico Earthquake Sequence

The January 7, 2020 M6.4 earthquake — which struck southwestern Puerto Rico near the town of Guánica — was the largest event in a sequence that began in late December 2019 and produced dozens of M4+ aftershocks over the following weeks. The earthquake killed 1 person, injured 9, and damaged or destroyed approximately 8,000 homes, with the most severe damage concentrated in the Guánica-Guayanilla corridor where older unreinforced masonry construction was prevalent and where the earthquake's shallow depth (8 km) and near-field epicenter produced intense ground motions.

The sequence was particularly damaging to Puerto Rico's already-stressed infrastructure — the island had not yet completed recovery from Hurricane María (2017), which had itself caused catastrophic damage to Puerto Rico's power grid, road network, and building stock. The compounding of a major hurricane disaster with a significant earthquake less than three years later in a small island economy with limited fiscal capacity illustrates the multi-hazard exposure that characterizes Caribbean island life in a way that no single-hazard analysis can fully capture.

Jamaica: Fault on Fault at the Plate Boundary

Jamaica sits astride the left-lateral Enriquillo-Plantain Garden Fault to its east and the similarly oriented Walton fault to its north — both accommodating the same Caribbean-North America relative motion that produced the 2010 Haiti earthquake on the EPGF. Jamaica's largest historical earthquake — the 1692 Port Royal event that opened this article — is estimated at M7.5 and remains the most destructive natural disaster in the island's recorded history. The 1907 M6.5 Kingston earthquake killed approximately 800 people and destroyed much of the capital. Both events occurred on the Enriquillo or Walton fault systems and both demonstrate that Jamaica's exposure is directly comparable to Haiti's on the same fault network.

The estimated recurrence interval for large earthquakes on the Walton fault based on paleoseismic evidence is 500–1,000 years — with the last major event being the 1692 earthquake. At 334 years since the last major rupture, the Walton fault may be accumulating strain toward another significant event on a recurrence interval that has already been reached or exceeded in the shorter part of its estimated range. Kingston, the Jamaican capital of approximately 600,000 people, is built directly within the near-field of the Walton fault and on a mix of alluvial and Kingston Harbour fill sediments highly susceptible to amplification and liquefaction. The institutional memory of the 1907 earthquake — the last damaging event felt by living generations — has been sufficient to maintain awareness in the earthquake engineering community but has not yet driven the scale of retrofit investment that the hazard assessment warrants.

Trinidad: South America's Edge in the Caribbean

Trinidad, the southernmost island of the Caribbean island chain, occupies an unusual tectonic position: it sits at the deforming northeastern edge of South America, at the zone where the Caribbean plate and the South American plate interact in a broad zone of transpressional tectonics. The El Pilar fault — a right-lateral strike-slip fault running east-west along the southern coast of Trinidad and continuing into Venezuela — accommodates much of the Caribbean-South America relative motion in this region and is capable of generating M7.0–7.5 earthquakes.

Trinidad's largest historical earthquakes — the 1766 M7.0 Cumana event and numerous M6+ events in the 20th century — occurred on the El Pilar and related fault systems and caused significant damage throughout the island. Trinidad's oil and gas industry — one of the most important in the Caribbean basin — is concentrated in the southern portion of the island directly adjacent to the El Pilar fault, creating a specific industrial infrastructure exposure to earthquake hazard that extends beyond the residential building stock to include refineries, petrochemical facilities, and marine terminals.

Caribbean Tsunamis: The Second Threat

In the Caribbean, earthquakes and tsunamis are inseparable hazards — the tectonic configuration of the region places tsunami sources on nearly every side. The Lesser Antilles subduction zone to the east can generate trans-Caribbean tsunamis from megathrust events comparable to the 1843 Guadeloupe event. The Puerto Rico Trench to the north is considered one of the most significant tsunami source zones for the region — a great megathrust event on the Puerto Rico Trench could send 3–5 meter waves across the northern Caribbean within 15–30 minutes. Strike-slip events on the Enriquillo-Plantain Garden, Walton, and El Pilar fault systems can also generate tsunamis if they have sufficient reverse-fault component or if they trigger underwater slope failures on the steep submarine flanks of the island platforms.

The 2004 Indian Ocean tsunami — which devastated countries with similar small island characteristics to the Caribbean nations — prompted significant investment in Pacific and Indian Ocean tsunami warning systems. The Caribbean Tsunami Warning Programme, operated through NOAA and the Intergovernmental Oceanographic Commission, has expanded the regional network of tsunami detection buoys and has established tsunami warning centers in Puerto Rico and elsewhere to provide regional warning capability. The challenge for the Caribbean, as for other small tsunami-vulnerable regions, is the short warning time available for locally generated events — a Puerto Rico Trench megathrust event would reach Puerto Rico's north coast in approximately 5–10 minutes, leaving essentially no time for organized evacuation and requiring the same "earthquake is the warning" behavioral response that characterizes coastal preparedness in Cascadia and the Pacific Northwest.

The Small Island Preparedness Challenge

The Caribbean's seismic risk presents a preparedness challenge that is qualitatively different from the challenges facing large continental nations with major earthquake exposure. The Caribbean consists primarily of small island developing states — nations with populations ranging from a few tens of thousands to a few million, economies heavily dependent on tourism, limited fiscal capacity for infrastructure investment, engineering workforces that are orders of magnitude smaller than those available in the United States or Japan, and governance structures that struggle to maintain even basic code enforcement in the building sector.

The 2010 Haiti earthquake is the extreme case of this vulnerability — a country that was already the poorest in the Western Hemisphere, with a history of political instability, minimal building code enforcement, and a concentration of population in an urban area built almost entirely without seismic design. The earthquake removed what little functional government existed, killed many of the country's most educated professionals (including large numbers of doctors and engineers whose buildings collapsed), and created a dependency on international humanitarian assistance that has persisted more than fifteen years later.

But the challenge is not unique to Haiti. Throughout the Caribbean, seismic codes have been adopted on paper — many Caribbean nations adopted the Caribbean Uniform Building Code (CUBiC) in the 1980s or have since adopted the International Building Code or local equivalents — but enforcement is inconsistent, the building sector workforce often lacks the training to implement the code provisions, and the majority of the existing building stock predates the codes and has not been assessed or retrofitted. In most Caribbean nations, as in most of the developing world, the critical seismic vulnerability is not the absence of a code but the gap between code requirements and actual practice in the field.

Conclusion

The Caribbean is one of the world's most beautiful regions — and one of its most seismically exposed. The tectonic configuration that produces the warm azure waters, the volcanic island landscapes, and the complex marine biodiversity of the Caribbean basin is the same configuration that generates major earthquakes on the Enriquillo fault beneath Haiti, the Walton fault beneath Jamaica, the Puerto Rico Trench offshore of San Juan, and the Lesser Antilles subduction zone beneath the volcanic arc. These are not distant, theoretical hazards — they are the historical record of the past three centuries, and they will recur on the timescales that the paleoseismic and historical record documents.

The challenge facing the Caribbean is not scientific understanding — the fault systems are mapped, the recurrence intervals are estimated, the hazard zones are defined with sufficient precision for building code and land use planning. The challenge is converting that scientific understanding into the physical resilience of the built environment in small, resource-constrained island nations where the next major earthquake will inevitably test whether the gap between scientific knowledge and practical action has been closed — or whether history will repeat itself in the pattern of Port Royal, Kingston, Guadeloupe, and Haiti.