UTIG RESEARCH PROJECTS ARCHIVE

TICOSECT

Investigation of Upper Plate Response to Subducting Plate Morphology and Seamounts at Subduction Zone Asperities: Cooperative German, Costa Rican and United States Project

Principal Investigators: Kirk McIntosh, Thomas Shipley, Yosio Nakamura, Paul Stoffa, Roland von Heune, Ernst Flueh, and German Leandro

Funded by: National Science Foundation

For a self-guided tour, click on any one of the three experiment locations in the map below.

TICOSECT Project Description

Observations of convergent margins worldwide suggest that the morphology and crustal thickness of a subducting plate may influence the tectonic features of the overriding plate including the mode of deformation, earthquake patterns, volcanic activity and composition, and crustal elevation. In particular, seamounts on the subducting plate may serve as earthquake nucleation sites or asperities. The TICOSECT Project has been designed to investigate these issues by obtaining seismic images of the crustal structure along the Cocos-Caribbean convergent margin where three morphologically different segments of the Cocos plate are currently subducting beneath Costa Rica.

In March-April 1995, geophysical data were acquired aboard the R/V Maurice Ewing within the smooth, seamount-dominated, and Cocos Ridge segments of the Cocos plate located offshore northern, central, and southern Costa Rica, respectively. A large marine airgun source, 20-30 ocean bottom instruments (seismometers and hydrophones), 30+ land instruments, and selected land shots were used to obtain wide aperture and near-vertical seismic data across the three regional transects. The wide aperture data have been used to establish crustal structure/velocity models across the arc and forearc areas which until now have been poorly known. The resulting models have also been used to migrate near-vertical seismic data recorded by the ocean bottom and land instruments. The migrated seismic data image the plate boundary zone reflections into the zone of seismogenic subduction. Along all three transects a primary goal is to construct accurate velocity models so that the images of the plate boundary zone from this project can be tied to relocated earthquake hypocenters. Integration of these two data sets could provide a missing link in our understanding of the transition from aseismic to seismogenic plate motion.