The Rivera microplate and the Cocos plate are subducting beneath the North American plate. To obtain new insights into the subduction geometry, we located earthquakes recorded by seismic stations deployed during the Mapping the Rivera Subduction Zone experiment from January 2006 to June 2007. We implemented standard procedures for earthquake location, and we also manually corrected phase detections and picks to increase accuracy of the earthquake catalog. We located about 2100 earthquakes within the 2.0–5.3 M L magnitude range. The average location error is 0.8 km horizontally and 1.0 km vertically, and the origin time has a mean error of 0.2 s. We observed crustal seismicity over the subducted Rivera microplate at no depth greater than 25 km; on the other hand, seismicity over the subducted Cocos plate is present to depths of 40 km. The Rivera plate shows a gently subduction angle near the trench, then dives more steeply into the mantle at an angle of 34° in the north and 37° in the south near the Colima graben. The distance between the inflection and the trench gradually increases from 40 km in the north of the study area to 60 km in the south near the Colima rift (CR). The Cocos plate has a slightly curved subducted slab with oblique geometry dipping toward the CR, ranging in dip from 18° in the south to 30° in the north.