Moment tensor solutions along the central Lesser Antilles using regional broadband stations

Using waveform data gathered from the seismological networks of the Lesser Antilles, we calculate 38 moment tensors for earthquakes with M ≥ 3, from 2013 to middle of 2015 by full waveform inversion. Nine of these moment tensor solutions are in good agreement with those previously reported by other institutions, it provides some guarantee for 29 new moment tensors for the central region of the Lesser Antilles. For earthquakes within the upper Caribbean lithosphere, our results evidence that extensional and strike-slip focal mechanisms are predominant, resulting from the intra-plate deformation produced by the subduction of the North America and South American Plates under the Caribbean Plate, whereas very few thrust events are observed. For deeper earthquakes (> 90 km), our results compare well with older focal mechanisms from previous studies, showing normal oblique or strike slip faulting within the subducted slab. However, the inversion for most of the deeper events is less reliable (as documented, for example, by their larger condition numbers). We use the newly obtained moment magnitudes to estimate the scaling relationship with the local magnitude MLv computed by the regional seismic network. The two magnitudes are consistent for earthquakes with magnitudes M > 4, with a slope close to unity. Further work is needed to precise the scaling relation for M < 4.