The earthquake arrived in a pair. The first shock rolled through the islands, and ten minutes later the second followed. Each produced its own tsunami, arriving roughly ten minutes after the shaking. In Frederiksted, on the western coast of St. Croix, the ground shook for a full minute, stirring a dust cloud that blanketed the town. The intensity reached IX on the Rossi-Forel scale across the Danish West Indies and the British Virgin Islands alike. In Fajardo, Puerto Rico -- the largest town in the earthquake's direct vicinity -- the church collapsed entirely, along with several civic structures. Parish churches in Bayamon, Cidra, and Juana Diaz sustained serious damage. The seismic energy radiated outward through a tectonic zone where the North American plate grinds beneath the Caribbean plate, a transition from subduction to strike-slip faulting that makes the Anegada Passage one of the most seismically volatile corridors in the Caribbean.

The tsunamis struck with devastating force across a wide arc of islands. At Christiansted on St. Croix, the waves drowned five people and pushed water far inland, destroying 20 houses and stranding boats well away from shore. Frederiksted was hit by surging seawater that beached multiple vessels, including the USS Monongahela, a Navy ship left helpless along the waterfront. At Road Town in the British Virgin Islands, the waves swept away much of the low-lying areas. In Antigua, the sea level rose noticeably at Saint John harbor. Little Saba recorded the highest wave heights of all. The USS De Soto, which had arrived just the day before, was ripped from her moorings and thrown onto the beach. The second wave then dragged the ship -- hull seriously damaged -- back out to sea. These were not abstract measurements. Each wave carried away someone's home, someone's livelihood, someone's sense of safety in a place already reeling.

The disaster did not end in November. On March 17, 1868 -- four months later -- an aftershock with a magnitude of 6.5 struck, accompanied by its own tsunami. The La Plata, a steamship serving the Royal Mail Steam Packet Company, was swamped by the wave. Nearly the entire crew perished. The timing of the aftershock became a minor historical puzzle: most reports documented it occurring in the morning, while one placed it in the evening, likely a typographical error. But there was nothing ambiguous about its consequences. The aftershock registered VII on the Modified Mercalli intensity scale -- classified as "Very strong" -- and demonstrated that the seismic threat had not passed with the initial event. The people of the islands lived with aftershocks and uncertainty for months.

Modern geologists have traced the earthquake to the Reid Fault, located south of St. Thomas on the northern scarp of the Anegada Trough. The fault runs for roughly 70 kilometers and may have ruptured with slip of up to 10 meters. The rupture likely began at a shallow depth of about 3 kilometers along a steeply dipping thrust fault -- a geometry that computer simulations suggest produced the unusually high wave heights. An underwater landslide triggered by the seafloor movement was probably the primary tsunami source, explaining why the waves arrived so quickly after the shaking. The Virgin Islands sit in a seismically active corridor where the Lesser Antilles subduction zone transitions to the Septentrional-Oriente strike-slip fault. The megathrust interface has not produced a major earthquake in recorded history, but the 1843 Guadeloupe earthquake -- estimated at magnitude 8.3 -- hints at the region's full destructive potential. The 1867 event was not an anomaly. It was a reminder.