Field geological and seismolgical investigations conducted after the Guinean earthquake on December 22, 1983 show a shallow dextral strike-slip fault with a large normal component. The NW-SE horizontal compressive stress deduced from this event is consistent with measurements made at other places in this region. Old fissures, some of them reactivated during this earthquake, show that this intraplate area constitutes a localized weakness zone in the crust.