The tremor hit yesterday some 33 kilometers north- northwest of Bahia de Caraquez and 36 miles north-northwest of Tosagua, the US Geological Survey said.
AFP reporters in the region felt some shaking but there were no reports of casualties or damage. No tsunami warning was issued.
It was one of numerous aftershocks following Saturday's 7.8-magnitude quake, the worst to hit the South American country in nearly four decades.
The official death toll from that quake rose to 587 yeesterday, with 5,733 injured. Scores of people are still missing.