TECTONIC BACKGROUND OF COLOMBIA

By Nelson Pulido (Kyoto University)

First of all the tectonic conditions of Colombia are extremely complex, because of the interaction of three plates: the Nazca plate, the South American plate and the Caribbean plate. The Nazca plate is subducting beneath South America from the west, which has produced several big subduction earthquakes in past (1979, Mw=8.1). Not less commom are the shallow earthquakes produced by the active faults in Colombia, that have a general orientation SW-NE.

The system of faults that produced the disaster of Armenia is called Romeral fault system, which also produced in June 6 of 1994 a Mb=6.4 strike-slip earthquake (the Paez earthquake) generating a devastating avalanche that killed around 1000 people.

It is a very important issue to locate the causative fault of the Armenia earthquake, that according to information of INGEOMINAS apparently did not have surface break.