Crustal Structure at the North Eastern Tip of Rivera Plate, Nayarit- Marias Islands Region: Scenarios and Tectonic Implications. Tsujal Project

Monday, 15 December 2014: 4:25 PM
Juanjo Danobeitia1, Rafael Bartolome1, Diego Córdoba Barba Sr2, Francisco J Nunez-Cornu3, William Lee Bandy4, Manel Prada1, Alejandra L. Cameselle5, Diana Nunez2, Juan-Manuel Espindola6, Ferran Estrada1, Azucena Zamora3, Adan Gomez3 and Modesto Ortiz7, (1)ICM-CSIC, Barcelona, Spain, (2)Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Madrid, Spain, (3)Universidad de Guadalajara, Centro de Sismología y Volcanología de Occidente, Puerto Vallarta, Mexico, (4)Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Mexico City, Mexico, (5)CMIMA-CSIC, Barcelona, Spain, (6)Universidad Nacional Autonoma de Mexico, Mexico City, Mexico, (7)Centro de Investigacion Cientifica y de Educacion Superior de Ensenada - CICESE, Oceanografía Física, Ensenada, Mexico
A primarily analysis of marine geophysical data acquired aboard the RRS James Cook in the framework of the project "Characterization of seismic hazard and tsunami associated with cortical contact structure Rivera Jalisco Block Plate (TSUJAL)" is presented. This survey was held in the region of Nayarit-Tres Marias Islands between February and March 2014. The examination of data recorded by 16 OBS 's, deployed along 4 wide angle seismic profiles is presented, using an airgun-array seismic source of 6800 c.i., which allows sampling the crustal structure to the Moho. The profiles are located along the margin off the Marias Islands: a profile of over 200 km NNW-SSE direction and parallel to the western flank of the Islas Marias Islands and three orthogonal thereto. These perpendicular sections sample the lithosphere from the north of Maria Madre Island with a profile of 100 km length, across Maria Magdalena and Mari Cleofas Islands, with a profile of 50 km long, till south of Maria Cleofas with a profile of 100 km long. Coincident multichannel seismic profiles with refraction ones are also surveyed, although shooting with a source of 3,540 c. i., and acquired with a digital "streamer" of 6.0 km long. Simultaneously, multibeam, parametric and potential field data were recorded during seismic acquisition

A first analysis shows an anomalously thickened crust in the western flank of the Marias Islands, as indicated by relatively short pre-critical distances of 30-35 km. While the moderate dip of 7 ° of the subduction of the Pacific oceanic plate favors somehow this effect, the existence of a remnant crustal fragment is also likely.

Moreover, the images provided by the parametric sounding show abundant mass wasting deposits suggesting of recent active tectonics, possibly generated by earthquakes with moderate magnitude as those reported in the Marias Islands. This set of geophysical data, not only provide valuable information for the seismogenic characterization and associated hazard with Rivera-Plate/Jalisco block, but it will also contribute to decipher the complex interplay between the accretion of the East Pacific Rise, the Magdalena Crest and the opening of the Gulf of California in the northeastern part of the diffuse Middle America Trench.