Die Struktur des aktiven Kontinentalhangs vor Nicaragua und Costa Rica: marin-seismische Steil- und Weitwinkelmessungen
This work constrains the structure of the active margin off Nicaragua and Costa Rica through the analysis of two coincident seismic reflection and refraction profiles. The modelling of the combined seismic datasets verified the structure and the P-wave velocities of the subducted oceanic Cocos Plate and the caribbean continental margin for an area ranging from central Nicaragua to neighboring Costa Rica. The existence of a shallow mantle sliver lying under the nicaraguan shelf is confirmed. Comparing the data presented in this study with gravity data and magnetic anomalies serves as a strong indication of an accreted terrain stretching as far as Guatemala. The imaging of deep cutting faults into the mantle, the modelling of low P-wave velocities of 7.2-7.8 km/s and a high Poisson ratio of 0.3 in the mantle, and gravity modelling support the assumption of a partially serpentinised mantle at the outer rise. Refraction data indicate a thickness of 3-13 km for this layer.