North American Plate
This part of Mexico lies on a complex convergent boundary where the Rivera Plate and the Cocos Plate are being subducted beneath the North American Plate. The transform boundary between the Rivera and Cocos Plates is poorly defined. This earthquake is thought to have ruptured the south-easternmost segment of the interface involving the Rivera Plate, although it may also have affected the north-westernmost part of the Cocos-North American Plate interface.