Résumé

In August 2010 a network of five hydrophones moored south of the Azores recorded an unusual earthquake swarm at the North FAMOUS and FAMOUS segments of the Mid-Atlantic Ridge (MAR). This earthquake swarm was comprised of >700 events, was focused off-axis, and extended spatially >70 km across the non-transform offset (NTO) separating the two segments. Acoustic waves of broadband spectrum (1-80 Hz) were generated by the onset of the swarm for >20 hours. A total of 30 earthquakes from the swarm were detected teleseismically, four had Centroid-Moment Tensor (CMT) solutions derived. The CMT solutions indicated three normal faulting events, and one non-double couple event. The spatio-temporal distribution of the seismicity and broadband energy show evidence of two magma dike intrusions at the North FAMOUS segment, with one intrusion crossing the NTO also evidenced by fine resolution of low MBA value. This may be the first intrusion event detected along the Northern Mid-Atlantic Ridge since the Lucky Strike segment intrusion observed in 2001.