Bayesian regional moment tensor from ocean bottom seismograms recorded in the Lesser Antilles: implications for regional stress field

SUMMARY Seismic activity in the Lesser Antilles (LA) is characterized by strong regional variability along arc reflecting complex subduction setting and history. Although routine seismicity monitoring can rely on an increasing number of island stations, island-arc means that high-resolution detailed studies fault structures require a network ocean bottom seismometers (OBS). As part 2016–2017 Volatile recycling at (VoiLA) project, we deployed 34 OBS stations forearc backarc. During deployment time, 381 events were recorded within zone. In this paper, perform full-waveform moment tensor (RMT) inversions, to gain insight into stress distribution depth. We developed novel inversion approach, AmΦB—‘Amphibious Bayesian’, taking account uncertainties associated with deployments. Particularly, orientation horizontal components (alignment uncertainty) high noise level them due microseisms are accounted for using AmΦB. The conducted direct, uniform importance sampling parameters multidimensional tree structure: uniXtree-sampling algorithm. show alignment components, particularly marine environments, influences obtained source mechanism when standard least-squares (L2) RMT schemes, resulting systematic errors recovered focal mechanisms including artificial compensated linear vector dipole (CLVD) contributions. Our Bayesian formulation AmΦB reduces these CLVD nearly 60 per cent aberration geometry as measured Kagan angle around 40 relative L2 inversion. Subsequently, use AmΦB-RMT obtain 45 (Mw > 3.8) MT solutions, out which 39 new any existing database. Combining our results subsequently analyse total 151 solutions classification (FMC) diagram map tectonic setting. also newly compiled database inversions LA On plate interface, observe typical compressional regime zone find evidence upper-plate strike slip normal behaviour north becomes near arc-perpendicular extensional towards south. A dominant slab perpendicular found 100–200 km beneath central arc. interpret condition be result pull varying partial detachment previously hypothesized lateral tear Grenada, southern end arc, leading reactivation pre-existing subducted Proto-Caribbean ridge.