S33A-4489:
Tomography of the East African Rift System in Mozambique 

Wednesday, 17 December 2014
Ana Domingues1,2, Graça M Silveira3, Susana Custodio4, Jose Chamussa5, Sergei Lebedev6, Sung-Joon Chang7, Ana M. G. Ferreira8 and Joao F B D Fonseca1, (1)Instituto Superior Técnico, Lison, Portugal, (2)Birkbeck, University of London, London, United Kingdom, (3)ISEL/IDL, Lisbon, Portugal, (4)Universidade de Lisboa, Lisbon, Portugal, (5)Direcçao Nacional de Geologia, Maputo, Mozambique, (6)Dublin Institute for Advanced Studies, Dublin, Ireland, (7)Kangwon National University, Chuncheon, South Korea, (8)University College of London, Department of Earth Sciences, London, United Kingdom
Abstract:
Unlike the majority of the East African Rift, the Mozambique region has not been deeply studied, not only due to political instabilities but also because of the difficult access to its most interior regions. An earthquake with M7 occurred in Machaze in 2006, which triggered the investigation of this particular region. The MOZART project (funded by FCT, Lisbon) installed a temporary seismic network, with a total of 30 broadband stations from the SEIS-UK pool, from April 2011 to July 2013.

Preliminary locations of the seismicity were estimated with the data recorded from April 2011 to July 2012. A total of 307 earthquakes were located, with ML magnitudes ranging from 0.9 to 3.9. We observe a linear northeast-southwest distribution of the seismicity that seems associated to the Inhaminga fault. The seismicity has an extension of ~300km reaching the Machaze earthquake area. The northeast sector of the seismicity shows a good correlation with the topography, tracing the Urema rift valley.

In order to obtain an initial velocity model of the region, the ambient noise method is used. This method is applied to the entire data set available and two additional stations of the AfricaARRAY project. Ambient noise surface wave tomography is possible by computing cross-correlations between all pairs of stations and measuring the group velocities for all interstation paths. With this approach we obtain Rayleigh wave group velocity dispersion curves in the period range from 3 to 50 seconds. Group velocity maps are calculated for several periods and allowing a geological and tectonic interpretation.

In order to extend the investigation to longer wave periods and thus probe both the crust and upper mantle, we apply a recent implementation of the surface-wave two-station method (teleseismic interferometry – Meier el al 2004) to augment our dataset with Rayleigh wave phase velocities curves in a broad period range. Using this method we expect to be able to explore the lithosphere-asthenosphere depth range beneath Mozambique.

Back to: Imaging the Earth VI Global and Regional Tomography of the Mantle Posters
<< Previous Abstract | Next Abstract >>