GEOMETRIC ASPECTS OF THE SUBDUCTION OF THE COCOS PLATE: IMPLICATIONS FOR THE ORIENTATION OF THE TRANS-MEXICAN VOLCANIC BELT

The Euler pole between the Cocos and North America Plates lies close to their convergent margin, the Middle America Trench. Because of this proximity, subduction along the northwestern portion of the trench takes place earlier than at the southeastern part. Consequently, segments of the same age along the northwest are subducted and bent before their corresponding segments along the southeast. Here, we model the geometry of subduction of the Cocos Plate underneath North America with this restriction and find that, strictly from geometric reasons, the northwestern portion must reach greater depths than their counterparts in the southeast, as found from distribution of earthquake foci by previous authors. As means of comparison and control, we also model the geometry of subduction of the Cocos Plate beneath the Caribbean and find no substantial difference in the dip of subduction along the convergent margin. Results suggest that the orientation of the Trans Mexican Volcanic Belt is controlled mostly by geometry of subduction.