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Imaging the Rivera and Cocos Plates Shape in Western Mexico From Local Seismicity Studies.

Description: 

A total of 5,220 hypocenters located in the region of Jalisco, Colima, and Michoacan states in western Mexico are used to study the subduction and geometry of the Rivera and Cocos plates beneath the North American plate. In our study, we observe that the geometry and seismic characteristics of the subduction at Jalisco Block, Colima Rift Zone, and Michoacan Block are different. The Jalisco Block is approximately 30 km thick. The contact between the Rivera plate and the Jalisco Block is tectonically complex and can be separated into at least four sections: two located between Bahía Banderas and Purificacion River and the other two between Purificacion River and Colima Rift Zone. South of Bahía Banderas, the slab is observed until 130 km with a dipping angle of 24°. In the Tomatlán River and San Nicolas River areas, the slab is observed until 85 km from the trench dipping 26°, while in the region of Purificacion River, the slab is divided into three segments with different dipping angles, up to 140 km from the trench. In the area of the Marabasco River, the slab can be observed in two segments, with dip angles of 26° and 35°, respectively, and up to 145 km from the trench. There is no evidence of a slab below the Colima Rift Zone due to seismicity being scarce, except in the Colima Volcano area and on the coast, where deep earthquakes (> 70km) are located below Colima Volcano that could be associated with the magmatic process. The crustal thickness in the Michoacán Block is 30 km. To the south, the Cocos Plate subducts with an angle between 24° and 30° and is slightly bent in the west direction. The Cocos plate seismicity related to the subduction process seems homogeneous, except for a seismic cluster at the mouth of the Coalcoman River, which corresponds to the epicentral area of the 1973 and 2021 earthquakes.

Session: Subduction Zone Structure From Trench to Arc

Type: Oral

Date: 4/19/2023

Presentation Time: 11:15 AM (local time)

Presenting Author: Francisco J. Nunez-Cornu

Student Presenter: No

Invited Presentation: 

Authors