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The northern E-W boundary of the Caribbean Plate is primarily left lateral and has evolved through the Cenozoic from transtensive to transpressive. The southern branch of this boundary, the Enriquillo-Plantain Garden Fault (EPGF), traverses southern Haiti through the Jamaica Passage to Jamaica. Damaging earthquakes occurred in Haiti in 1751, 1770, 2010 and 2021, and in Jamaica in 1692 and 1907, yet the Jamaica Passage segment has little known seismicity with no large historic events. The EPGF in the Passage follows a 2-3 km deep trough that is less oblique to the plate motion, and was imaged previously by the 2012 HAITI-SIS seismic cruise. We present the results of an NSF-funded RAPID cruise carried out in January 2022 to the Jamaica Passage, that investigated the EPGF with a hi-res multichannel seismic system collecting >650 km of data and 47 sediment cores. We observe prominent scarps along the EPGF consistent with large seismogenic displacements, and discovered widely distributed event deposits in the cores (McHugh et al. abstract). Imaged Neogene shortening structures verge southward, and are consistent with reactivation under compression. Shortening decreases from east to west. The Matley (eastern) and Navassa (central) sub-basins feature imbricate thrusting along their northern flanks, and the Morant (western) sub-basin features open folding flanked by unfolded sediments in its central part. At the depths imaged by our data, the strain is mostly partitioned: The EPGF is sub-vertical with no consistent vertical offsets, thus accounting for only sinistral motion sub-parallel to the fault, while shortening is directed across the basins. Structures point to two distinct stress components: a regional one that drives transpression, and a spatially variable one close to the EPGF, possibly in response to minor bends along this fault. Extensional and contractional structures are superimposed at distinct times on the north flank of the EPGF, as expected of a fault that translates relative to the causative fault bends. This is an important feature related to the major fault bend west of the Morant Basin, marking the transition between the Passage and the Jamaica segment of the EPGF. The results will help us better understand the tectonics of the region and its earthquake history, and to assess the hazard for future events. 

Recent GPS studies show that the Indo-Burma subduction system is locked with the implication of a potential large-magnitude earthquake. To inform better seismic hazard models in the region, we need an improved understanding of the crustal structure and the dynamics of the Indo-Burma subduction system. The Bangladesh-India-Myanmar (BIMA) tripartite project deployed 60 broadband seismometers across the subduction system and have been continuously recording data for ~2 years. In this study, we computed receiver functions from 30 high-quality earthquakes (M≥5.9) with epicentral distances between 30º and 90º recorded by the array. The algorithm utilized ensures the uniqueness of the seismic model and provides an uncertainty estimate of every converted wave amplitude. We stacked all the receiver functions produced at each station along the entire transect to generate a cross-sectional model of the average crustal structure. The level of detail in the image is improved by computing higher frequency receiver functions up to 4 Hz. The results represent some of the strongest constraints on crustal structure across the subduction system. Beneath the Neogene accretionary prism's outer belt, we observe a primary conversion associated with the Ganges Brahmaputra Delta that ranges in depth from ~10 km near the deformation front up to ~12 km at the eastern boundary. From the eastern end of the Neogene accretionary prism to the Sagaing Fault, we image the Indian subducting slab and the Central Myanmar basin. The depth-extent of seismicity associated with the Wadati-Benioff zone is consistent with the locations of primary conversions from the subducting plate. We further verify the converted phases of the slab by analyzing azimuthal moveout variations. The Central Myanmar basin is roughly bowl-shaped in cross-section with a maximum thickness of ~15 km about halfway between the Kabaw and Sagaing faults. The average crustal thickness beneath the Ganges-Brahmaputra delta is ~20 km, most likely representing a transitional crust formed from thinning of the continental crust intruded and underplated by igneous rocks. In contrast, the average thickness of the continental crust beneath the Central Myanmar basin is ~40 km. Our results provide a baseline model for future geophysical investigations of the Indo-Burma subduction zone.