Diagnosis of the time of increased probability of earthquakes of magnitude 5.5 or greater in the Lesser Antillean arc

Abstract

The intermediate-term premonitory seismicity pattern before a strong earthquake (magnitude 5.5 or greater) in Lesser Antillean arc can be diagnosed using the earthquake catalogue issued by the Département des Observatoires of the Institut de Physique du Globe de Paris. The CN algorithm, applied to this catalogue, identifies two times of increased probability of such earthquakes: the first precedes the only strong earthquake (16 March 1985, M 1 (local magnitude) = 6.2), which occurred during the period considered; the second is a current alarm. During both times of increased probability, the seismic activity increased above a depth of 40 km and decreased below it. The results suggest at least a partial similarity in subduction zones of this type and in other seismotectonic environments where the algorithm was previously applied. Shallow earthquakes make a major contribution to formation of the patterns considered.