Moment tensor solutions and stress regime along the Northern Caribbean plate boundary off southeastern Cuba

For a better understanding of the kinematics and mechanics of the Oriente transform fault, a left‑lateral boundary along Cuba's southern margin in the Caribbean, we use the seismic records to determine new deviatoric moment tensor solutions by full waveform inversion for 49 earthquakes, magnitude range 6.8 > M > 3.5, along the southeastern coast of Cuba, from 2015 to the end of 2024. We validate our results using 14 events with moment tensors independently determined by other agencies. The moment tensor solutions calculated here, together with 16 historical ones from the gCMT database, highlight the along-strike segmentation of the Oriente fault system, with oblique normal faulting in the Cabo Cruz transtensional step-over, and oblique reverse faulting further east in the Oriente Deep Zone and the transpressional Santiago Deformed Belt. The Oriente fault, though largely strike-slip, may have a small reverse component itself, as exemplified by the November 10, 2024, Mw 6.8 earthquake. The bulk of reverse/oblique faulting earthquakes, however, coincide with the Santiago Deformed Belt, a narrow crustal sliver overthrusting to the south the extended island arc crust of the eastern Cayman Trough and likely bounded to the north by the Oriente fault. The moment magnitudes computed agree well with the local magnitudes for Mw > 4, as expected. For Mw < 4, we find Mw ≈ 0.67 ML, similar to other regions, for instance the Lesser Antilles.