Lücke, Oscar H., Götze, Hans-Jürgen and Alvarado, G. E. (2012) Density Structure of the Central American Lithosphere from Satellite Derived Gravity Data: highlighting the need for data acquisition at a level between the Earth's orbit and its surface. [Poster] In: The Lübeck Retreat, Collaborative Research SFB 574 Volatiles and Fluids in Subduction Zones: Climate Feedback and Trigger Mechanisms for Natural Disasters. , 23.-25.05.2012, Lübeck, Germany . The Lübeck Retreat: final colloquium of SFB 574; May 23-25, 2012: program & abstracts. ; p. 18 .

Abstract

Gravity data from the combined geopotential model EGM2008 was interpreted via forward modelling
to outline the three dimensional lithospheric density structure along the Middle American Trench, as
well as the segmentation of the oceanic Cocos and Nazca plates and the overriding Caribbean Plate.
Results for the Moho depth obtained from the density model are presented. The Quaternary volcanic
arc correlates with a maximum Moho depth of 44 km in western Guatemala. To the southeast of the
continental shelf, the Caribbean plate shows Moho depths between 20 and 12 km whereas to the
north, values as shallow as 8 km are observed at the Cayman trough. For the oceanic Cocos Plate,
depths between 16 and 21 km are obtained for the Moho along the Cocos ridge contrasting with
values between 15 and 12 km for the seamount segment and 8 and 11 km for the segments of the
crust that are not affected by the Galapagos hot-spot track. These results were obtained from regional
scale modelling of first order lithospheric discontinuities. Combined geopotential models such as
EGM2008 based on gravity data from the GRACE mission, satellite altimetry offshore and surface
gravity measurements onshore, and the latest EIGEN-6C which additionally includes data from the
LAGEOS and GOCE satellite missions, have proved to be a viable source of data for the regional
scale modelling of the solid Earth. The current combined models possess sufficient spatial resolution
for the interpretation of first order lithospheric discontinuities such as the Moho, the lithosphereasthenosphere
boundary and the subducted slab. However, for the shorter wavelengths, the
combined models still rely on the coverage of surface gravity stations. In Costa Rica, the available
gravity databases lack coverage in certain key areas. This lack of coverage is associated with regions
in which ground access is not possible due mainly to: rugged topography, vegetation coverage, and
lack of infrastructure. In order to achieve a satisfactory coverage of these areas and the spatial
resolution necessary for local scale models, an intermediate level between the orbit and the surface is
needed. For this reason, an airborne gravity survey is planned and should provide comprehensive
data coverage of the Costa Rican landmass and the necessary spatial resolution for the modelling of
local structures.

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