Density Structure and Geometry of the Costa Rican Subduction Zone from 3D Gravity Modelling and Local Earthquake Data

Lücke, Oscar H. and Arroyo, Ivonne G. (2015) Density Structure and Geometry of the Costa Rican Subduction Zone from 3D Gravity Modelling and Local Earthquake Data Solid Earth, 6 (4). pp. 1169-1183. DOI 10.5194/se-6-1169-2015.

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The eastern part of the oceanic Cocos Plate presents a heterogeneous crustal structure due to diverse origins and ages as well as plate-hot spot interactions which originated the Cocos Ridge, a structure that converges with the Caribbean Plate in southeastern Costa Rica. The complex structure of the oceanic plate directly influences the dynamics and geometry of the subduction zone along the Middle American Trench. In this paper an integrated interpretation of the slab geometry in Costa Rica is presented based on 3-D density modeling of combined satellite and surface gravity data, constrained by available geophysical and geological data and seismological information obtained from local networks. The results show the continuation of steep subduction geometry from the Nicaraguan margin into northwestern Costa Rica, followed by a moderate dipping slab under the Central Cordillera toward the end of the Central American Volcanic Arc. Contrary to commonly assumed, to the southeast end of the volcanic arc, our preferred model shows a steep, coherent slab that extends up to the landward projection of the Panama Fracture Zone. Overall, a gradual change in the depth of the intraplate seismicity is observed, reaching 220 km in the northwestern part, and becoming progressively shallower toward the southeast, where it reaches a maximum depth of 75 km. The changes in the terminal depth of the observed seismicity correlate with the increased density in the modeled slab. The absence of intermediate depth (> 75 km) intraplate seismicity in the southeastern section and the higher densities for the subducted slab in this area, support a model in which dehydration reactions in the subducted slab cease at a shallower depth, originating an anhydrous and thus aseismic slab.

Document Type: Article
Additional Information: WOS:000374540800005
Keywords: Gravity anomalies and Earth structure; Subduction zone processes; Seismicity and tectonics; Cocos Plate; Caribbean Plate
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
DOI etc.: 10.5194/se-6-1169-2015
ISSN: 1869-9529
Projects: SPP 1257
Date Deposited: 18 Dec 2012 11:37
Last Modified: 02 Jun 2016 09:14

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