Rupture length and velocity for earthquakes in the Mid-Atlantic Ridge from directivity effect in body and surface waves

The dimensions and rupture velocities of four earthquakes, two in the Mid-Atlantic Ridge and two in Iceland with strike–slip mechanisms and magnitudes (M_w) between 6.2 and 6.8 were studied using the directivity effects of Rayleigh and body waves. For Rayleigh waves we used the directivity function for different pairs of stations and for body waves the waveforms of P and SH waves corresponding to a simple extended line source. We have found that three have very shallow depths about 3 km and one 8 km, fault lengths between 12 km and 21 km, and a low rupture velocity of about 1.5 km/s to 2.0 km/s which supports the idea of the presence of slow earthquakes in transform faults.