Current states of stress in the northern Andes as indicated by focal mechanisms of earthquakes

Deep seismicity (about 150-170 km) concentrates in the Bucaramanga nest and Cauca Valley areas. The inversion reveals a rather homogeneous attitude of the minimum stress axis, which dips towards the E. This extension is consistent with the present plunge of the Nazca and Caribbean slabs, suggesting that a broken slab may be torn under gravitational stresses in the Bucaramanga nest. This model is compatible with current blocking of the subduction in the western northern Andes, inhibiting the eastward displacement of slabs, which are forced to break and sink in to the asthenosphere under their own weight.