Tonight at 00:23 Italian time (23:23 UTC, 18:23 in the Cayman Islands), a powerful magnitude 7.4 earthquake (7.6 according to the USGS; 7.5 according to the German GFZ) occurred in the Caribbean Sea, about 200 km southwest of Georgetown in the Cayman Islands and about 400 km west of Jamaica.
Due to its high magnitude, the earthquake triggered tsunami warnings for surrounding countries (in addition to those already mentioned, Cuba, Honduras, Nicaragua, Mexico, the Bahamas and others). The Pacific Tsunami Warning Center sent the first alert message at 23:29 UTC, six minutes after the earthquake, estimating a magnitude of 8.0, much stronger than the final estimate. At 23:42 the estimate was revised to 7.6 and the alert message downgraded, but kept active for the nearest countries.
INGV's Tsunami Alert Centre (CAT) analysed the event in real time, although it was not in its area of competence (which is limited to the Mediterranean). In fact, earthquakes are monitored on a global scale for training purposes and verification of procedures.
The alert ended after about two and a half hours, without a major tsunami occurring (only a few centimetres observed in some of the tide gauges in the Caribbean Sea). This is because the earthquake occurred along a well-known transcurrent fault (see figure) and in fact the focal mechanism of the event shows a plane oriented approximately east-west that coincides with the known fault. Transcurrent earthquakes have the characteristic of causing a mainly lateral displacement of the two sides of the fault, while it is the vertical movement of the seabed that can generate a tsunami.