Ocean-bottom seismograph observations on the Charlie—Gibbs fracture zone

Summary. Two networks of four ocean-bottom seismographs were deployed successfully in 1982 September on spreading centre sites in the region of the Charlie–Gibbs fracture zone. Activity was observed beneath both networks and hypocentres for over 100 events have been determined. The observations confirm the existence of seismic activity along a suspected short spreading centre near longitude 31.75°W linking the north and south transform valleys of the fracture zone. A relatively thick (7–9 km) seismogenic zone is seen beneath the axis which is in agreement with earlier microearthquake observations on the Mid-Atlantic Ridge.