An overview of ongoing studies on the lateral changes of the plate-boundary structure of Middle America, the 3D multichannel seismic experiment at the CRISP area, and the north Chile region

Abstract

We will present an overview of recent activities offshore Pacific Central America that originated from related to the SFB. Current work includes the integration of existing seismic data and earthquake rupture models of Costa Rica and Nicaragua analyzed trying to understand the relationship between mega-thrust fault properties and seismogenesis. We will also present a preliminary interpretation of 2D seismic data around Osa Peninsula in the light of the recent CRISP iODP leg 334 drilling results and multibeam bathymetry. The CRISP area was surveyed in 2011 with a new 3D multichannel seismic data collected to prepare iODP expedition 344 and the deep riser drilling. The data were collected with USA R/V Marcus G. Langseth using 4 streamers, 6 km long and 2 well tuned 3400 c.i. airgun arrays. The data have been commercially processed by Repsol-CGG (Madrid) and ongoing work will focus of 3d pre-stack depth migration (Repsol, Houston). Preliminary post-stak time migrations of the 3D data show promising images of the deformation of the overriding plate and plate boundary reflections. Work continues in northern Chile with the Cinca project seismic data and a compilation of multibeam bathymetry. A set of seismic profiles collected perpendicular to the margin shows that the ocean plate bending-related deformation, involving the mantle, initiates well before the lithosphere plunges into the trench. Also the combination of seismic images and swath bathymetry shows a remarkable lateral variability in the intensity and style of deformation at the trench. The deformation appears to be controlled by the combined effect of changes in trench strike and preexisting ocean plate structure, and changes abruptly along the subduction zone