abstract On September 26, 1970, three main earthquakes, followed by over 300 aftershocks, caused havoc in Puerto Mutis and neighboring towns on the Pacific Coast of the Department of Chocó, Colombia. It was the first time in the seismic history of Colombia that an old fault showed clear signs of rejuvenation. The total earthquake damage is calculated as $200,000. Although no one was killed, and only two people injured, 39 per cent of a total of 287 houses collapsed completely, and one-third of the 2,400 frightened inhabitants of Puerto Mutis were evacuated through the good offices of the Navy and Air Force, by air and sea, these being the only means of transport between Puerto Mutis and the interior of Colombia. Most of the hypocenters were normal. However, the three main shocks of September 26 had depths of about 10 km only. They took place at 12h02m29s and 14h57m02s on September 26 and at 03h38m36s on September 27 (G.M.T.). These earthquakes were felt in the central and northwestern part of the Republic and caused minor damage in the nearby towns of the sea coast.