The Rivera plate is believed to have separated from the Cocos plate located to its southeast about 5–10 million years ago. Seismicity and tomography images show that the Rivera plate dips at 40° beneath the forearc region and then dips ~70° beneath the Trans-Mexican Volcanic Belt. The subduction of the Rivera plate under the North American plate, in the Mid-American Trench, has been the cause of the strongest earthquakes in the history of Mexico, including the largest earthquake in Mexico during the 20th century which occurred on June 3, 1932 in the state of Jalisco. The quake had a magnitude of 8.2 with a magnitude 7.8 aftershock, both of which caused widespread casualties and damage.
On October 9, 1995, a magnitude 7.6 earthquake occurred beneath the Jalisco region and caused significant loss of life and property.
Pardo, Mario; Suárez, Gerardo (1993), "Steep subduction geometry of the Rivera Plate beneath the Jalisco Block in western Mexico", Geophysical Research Letters, 20 (21): 2391–2394, Bibcode:1993GeoRL..20.2391P, doi:10.1029/93GL02794