Other
Scientific paper
May 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agusm.t32a..02g&link_type=abstract
American Geophysical Union, Spring Meeting 2007, abstract #T32A-02
Other
8170 Subduction Zone Processes (1031, 3060, 3613, 8413)
Scientific paper
The subduction zone of western Mexico is a unique region on Earth where microplate capture and overriding plate disruption are occurring today. The small Rivera plate is subducting beneath western most Mexico primarily beneath Jalisco state while to the east it is the Cocos plate that is subducting. Above the Rivera plate the Jalisco block of Mexico is bounded by the north trending Colima Rift and the northwest trending Tepic-Chapala Rift and may form a microplate in its own right. Magmatism is present throughout the region and is unusual for a subduction zone in that geochemical analyses indicate an ocean island basalt component to some of the lavas. Also, Colima volcano is offset trenchward from other volcanoes in the Mexican Volcanic Belt. Little is known of the subducting Rivera plate geometry due to the paucity of seismicity within the plate yet the geometry of the Rivera and Cocos plates at depth are likely critical for understanding the tectonic evolution of western Mexico. The MARS (MApping the Rivera Subduction zone) project consists of the deployment of 50 broadband seismometers covering the Jalisco block from the coast to the Tepic-Chapala rift in the north and about 150 km to the west of the Colima rift. The instruments were deployed in January, 2006 and will be removed in June, 2007. The goal of the project is to seismically image the subducting Rivera and Cocos plates at depth as well as the mantle wedge above the plates. A number of different analyses of MARS data are underway including teleseismic tomography, receiver function analysis, and shear wave splitting analysis. The preliminary tomography results clearly show both subducting plates with a sharp change in dip to the east of the Colima rift probably indicating a tear between the two plates along a trend more eastward than the trend of the rift. The images also show extremely slow shallow mantle velocities beneath the Tepic-Chapala rift but not beneath the Colima rift. Receiver functions indicate an average Moho depth of roughly 40 km in the continental interior but are very complicated near the coast. Finally, shear wave splitting observations indicate a generally north fast direction with a reduction in magnitude of splits beneath the Colima rift.
Dominguez Reyes T.
Gómez González J.
Grand Stephen P.
Guzman Speziale M.
Leon-Soto G.
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