This project is to observe deformations along 2500 km of one of the world's most prolific generators of large and great earthquakes, the Chilean convergent plate margin. The proposed distribution of regional GPS observing sites is focused on measurements of deformation of the region immediately above the main interplate seismic zone, but includes stations on the Nazca plate and sites across the Andes to establish the overall plate motions and deformations within the Andean orogen. This regional GPS network would be observed every two years during six week campaigns with receivers utilized in a pattern of fixed and leap- frogging mobile deployments. During the intervening years subsidiary campaigns mounted using 5 or 6 receivers would implement a program of spatial densification at specially selected parts of the regional network. Approximately 40-60 sites would abe observed during each subsidiary campaign. The primary short-term scientific objective is to measure seismic and aseismic deformations in the cycle of major interplate earthquake recurrence in relation to plate convergence and the tectonics of the subduction zone. The secondary, longer-term objective is to observe the horizontal and vertical deformations with the forearc and across the Andean cordillera. The proposed consortium includes U.S. experts in GPS deployment and data analysis; South American seismicity, tectonics and field operations; and strong ties with Chilean, Argentine and Bolivian scientists and the national geodetic surveys.
