Strike-slip faults are thought to create lower magnitude earthquakes and smaller tsunamis, if at all, compared to subduction zones. However, strike-slip faults have recently produced tsunamis larger than anticipated, highlighting that their seismic and tsunamigenic potential is likely underestimated. It is therefore necessary to characterize strike-slip fault architecture, fault slip modes, and slip rates to best understand their seismic and tsunamigenic potential. We present here a multi-disciplinary project for the Northern Caribbean plate boundary where a twin active strike-slip fault system exists, namely the Septentrional-Oriente Fault Zone (SOFZ) and the Enriquillo-Plantain Garden Fault Zone (EPGFZ). Both fault zones have onshore and offshore segments that create devastating earthquakes and sometimes induce tsunamis. Two major life-altering earthquakes – 2010 and 2021 – have recently occurred along the western onshore portion of the EPGFZ. These earthquakes highlight the urgency to investigate the SOFZ and EPGFZ, both onshore and offshore. With the amphibious CAST project, we aim to identify their fault architecture, unravel their seismotectonic history, and characterize their earthquake activity to better understand the associated hazards.