In the north Andes, borehole breakouts suggest a contemporary stress regime with the maximum horizontal stress (SH_max) oriented WNW-ESE to NW-SE, roughly parallel to the direction of shortening predicted by earthquake focal mechanisms, neotectonic stress indicators and other borehole breakout studies.

Unprocessed dipmeter logs from sixty ECOPETROL exploration wells were analyzed using Logman, a Quickbasic digitizing and dipmeter log analysis program. The data naturally fall into northern, central and southern subsets with mean SH_max orientations of 117^o, 111^o, and 133^o respectively. This variation with latitude may reflect changes in tectonic regime with latitude.

Several factors other than tectonic stress may be affecting the orientation of maximum horizontal compression. In the Putumayo Basin (southern subset), it appears that the in situ stress in three of the eight wells is influenced by the stress regime around a local fault. In the Llanos Basin (central subset), the orientation data are scattered to a depth of approximately 8,000 ft, and then cluster into two populations corresponding to SH_max of 110^o and 70^o. This change in breakout behaviour is attributed to either a change in lithology or the presence of a bedding plane fault at this depth. Because most wells are located away from major topographic features, topography does not seem to play a large role in this study, although it cannot be ruled out for the few wells located near areas of high relief.