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www.sea-technology.com October 2015 / st 25 I n February and March 2014, Spanish, Mexican and Brit- ish scientists and technicians explored the western margin of Mexico, a region with a high occurrence of large earth- quakes (> Mw = 7.5) and tsunami generation, on board the British Royal Research Ship James Cook. A dense geophysi- cal data set was acquired using the large seismic facilities from Spain's Consejo Superior de Investigaciones Cientif- cas (CSIC) and the acoustic, hull-mounted echosounder and seismic sources operated by the British Natural Environment Research Council (NERC). This successful joint cruise was made possible thanks to a cooperative agreement between NERC and CSIC as part of the Ocean Facilities Exchange Group (OFEG), a major fo- rum of European oceanograph- ic institutions for the exchange of ship time, equipment and personnel. Data obtained during this geophysical survey include images of the Rivera and Co- cos Plates crustal structure subducting beneath the North American (NA) Plate, where the active subduction can trig- ger signifcant earthquakes and tsunamis. The data are crucial to es- timating fault seismic param- eters for tsunami modeling and geohazards mitigation. Background The western boundary of the NA Plate from 22° N to 14° N is an active convergent margin where the Rivera and Cocos Plates subduct beneath the NA Plate, with the Middle America Trench (MAT) being the morphological expression of this convergence. The convergence rate of the Rivera Plate with respect to the NA Plate is moderate, about 2 to 3 cm/yr. The MAT extends from the Tres Marias Islands, locat- ed at 21° N, south of the Gulf of California, southward along the Mexican coast for about 3,000 km, but its width is only 40 to 60 km between the axis of the trench and the coast. The macroseismic history of the Jalisco region dates back to the year 1544. In the last 120 years, 10 major earthquakes Seismic Research In Western Mexico Collaborative Earthquake, Tsunami Hazard Investigation in Rivera Plate By Dr. Rafael Bartolome • Dr. Juanjo Dañobeitia • Dr. Diego Cordoba A map of the study area, show- ing the major tectonic fea- tures—EPR: East Pacifc Rise, MAT: Middle America Trench, OFZ: Orozco Fracture Zone, TME: Tres Marias Rise.