2015 SPA - Mireia Peral - The use of gravity gradients from GOCE satellite data in interpreting major crustal and lithospheric structures: application to the Iberian Peninsula

[This post is participating at the 2015 Student Presentation Awards at ICTJA]

Gravity is used in geophysics to study the Earth’s interior. Gravity prospecting measures variations of the Earth’s gravity field in order to find out density contrasts. In 2009 the European Space Agency (ESA) launched GOCE satellite (Gravity field and steady-state Ocean Circulation Explorer) aiming at determine  both Earth’s mean gravity field and geoid with high accuracy and spatial resolution. The satellite was equipped with an innovative Electrostatic Gravity Gradiometer that measures spatial variation of gravity (gravity gradients) in the three dimensions. This study has been done with the objective of analyze the information provided by gravity gradients and finding out the minimum features of geological structures that may be studied using GOCE data.

Gravity gradients, although characterized by less power signal, carry more information about geological structures than gravity measures alone. Gravity gradients are calculated over the Iberian Peninsula from a global gravity field model. We study the correlation between these signals and the topography of the region, as each gravity gradient component provides us specific information about geological structures.

On the other hand, the potential of GOCE data is studied by forward modelling of gravitational fields using the Tesseroids software. Gravity gradients produced by several synthetic models are computed and compared with the uncertainty of GOCE data. Varying some parameters of these prisms such as dimensions, depth and density, we identify the main characteristics of geological structures that could be detected by GOCE satellite. We find that the smallest dimensions of the structures that still generate enough signal in the vertical component vary from around 22.5 x 7.5 x 2.5 km if the density contrast with the surrounding media is 500 kg/m³ to 49.5 x 16.5 x 5.5 km if the density contrast is 50 kg/m³, with a maximum burial depth of 40 km. Moreover, a synthetic rift model (divergent plate boundary) is implemented in order to observe the gravitational gradient field generated by a common geological structure. Our results indicate that typical rift structures can be detectable by GOCE satellite.

Figure. Gravity gradients of the three main components computed at 255 km mean satellite altitude over the Iberian Peninsula region. a) g_xx: horizontal component in the North-South direction. b) g_yy: horizontal component in the East-West direction. c) g_zz: vertical component.

This work is supervised by Manel Fernandez and Montserrat Torne from the ICTJA-CSIC, Barcelona.