Excellent control is required of material mass-balance and residence time in the prism, in addition to detailed structural geometry of the complex interior regions of forearcs. Such control and imaging is not well established in any convergent margin, despite expending a great amount of effort to understand these margins. Inset shows map of Central America, Cocos Plate, and Caribbean Plate. The stippled rectangle shows the location of the 3D seismic grid. The longer lines are 2D profiles.
Vertical scale is in two-way traveltime.
The major objective of Site 1039 was to serve as a reference site for drilling in the Costa Rica subduction complex. LWD was a high priority for Site 1040, as it was for Site 1039. Comparison of LWD data from Site 1040 and Site 1039 could provide us with a record of density and porosity of unprecedented detail between a reference site and an underthrust sedimentary section. The prime objective of this site was to determine the nature and composition of the prism material underlying the slope apron. Site 1043 was designed to test whether or not offscraping is temporally and spatially intermittent.