Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica.
Journal of Geophysical Research-Solid Earth. 109 10.1029/2003jb002931 Abstract
 New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 +/- 2 and 39 +/- 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the rupture zone for future large earthquakes, at least over the short (similar to 1 year) observation period. We also estimate northwest motion of a coastal "sliver block'' at 8 +/- 3 mm/yr, probably related to oblique convergence. In the Osa region to the south, convergence is orthogonal to the trench. Cocos-Caribbean relative motion is partitioned here, with similar to 8 cm/yr on the Cocos-Panama block boundary ( including a component of permanent shortening across the Fila Costena fold and thrust belt) and similar to 1 cm/yr on the Panama block - Caribbean boundary. The GPS data suggest that the Cocos plate - Panama block boundary is completely locked from similar to 10 - 50 km depth. This large locked zone, as well as associated forearc and back-arc deformation, may be related to subduction of the shallow Cocos Ridge and/or younger lithosphere compared to Nicoya, with consequent higher coupling and compressive stress in the direction of plate convergence.
The gravitational edge effect.
Journal of Geophysical Research. 80:2949-2950., Washington, DC, United States (USA): American Geophysical Union, Washington, DC 10.1029/JB080i020p02949 Abstract
The knowledge that a gravity anomaly is due to an edge effect is sufficient to resolve the inherent ambiguity of the inverse potential problem. Thus given the gravity field across the contact between two laterally uniform structures, the density difference between the adjacent sections can be calculated by means of integral transforms operating on the data. The Backus-Gilbert inversion technique allows a rational trade-off between accuracy and resolution. The kernels associated with the physics of the problem indicate a resolution comparable to that of surface waves.