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    Project Title
    KINematics of the Eastern Margin of Africa (KINEMA)


    Project Reference
    PTDC/CTE-GIN/64101/2006
 

    key-words
    Plate Boundary; Present-day Tectonics; Space Geodesy; Southeastern Africa

 

    Starting Date
    PTDC/CTE-GIN/64101/2006

 

 

    Description of the Project

The African continent is divided over two major tectonic units, Nubia and Somalia. The plate boundary between these two plates is located on the eastern part of the continent, extending from the Afar Triple Junction in the North until the Southwest Indian Ridge in the South. However, the
exact location of the plate boundary is unknown in many parts of its extension, as well as the mechanisms that affect the behavior of these two plates on the deforming plate boundary zone. Furthermore, the existence of several blocks acting as transfer units between these two plates have been hypothesized, in particular in the South-East Africa, the region that is the focus of this study. Continuously-operating stations (CGPS) are the best option to estimate secular tectonic motion at discrete locations due to the large number of observations, which allows one to estimate and remove/reduce the contribution due to other natural and/or artificial, periodical and/or random
processes. However, in many cases, the only alternative to carry out geodynamic studies based on space-geodetic data is to use GNSS observations acquired in sporadic-observed networks. This is the current situation in Mozambique, where the only existing continuously-operating GNSS system in the country was installed in April 2006 in Nampula in a self-supported effort of the proposed KINEMA research team. However, in the framework of other projects, valuable GPS campaign-type observations were acquired all over the territory (135 stations were occupied between 1995 and 2004). For most stations, the time-span between the initial epoch and the epoch of the new proposed observation campaigns (up to 14 years) will be long enough to mitigate most of the error sources derived from the fact that the available dataset was not observed for geodynamic study proposes. In this aspect, efforts will be carried out to select the most accurate models and state-of-art methodologies to process GPS campaign data. Methods to reduce the influence of periodical signals in the time-series will be investigated, together with effects due to loading processes. Although we will focus on the use of space-geodetic data to study the present-day tectonics of South-East Africa, we also aim to explore synergies between several disciplines in order to contribute for the better understanding of the present-day kinematics of this region. Based on the quality of the GPS derived solutions for the entire initial dataset and in collected geophysical and geological information, a sub-set of about 40 stations will be selected. Other criteria for the selection will be the existence of reoccupations already in the past (which allow us to better assess the motion station quality) and an even geographical distribution over Mozambique. The objective is to select the best sub-set of stations per possible tectonic block (as defined by geophysical and geological constraints) that will allow us to assess the existence of these blocks and to quantify their differential motion. These stations will be reobserved twice during the execution of the project in order to derive reliable horizontal motion estimates. The computation of the GPS solutions will be carried out using two different processing software packages: GIPSY and GAMIT. The comparison of the solutions will identify eventual problems in the data quality, providing in this way more reliable position and motion solutions. As a result of this project, a present-day strain rate field will be produced for the South-East Africa region. The space-geodetic derived strain field will be compared and integrated with geophysical and geological data in order to identify the possible active deforming regions in South-East Africa.
Besides the computation of the near-field velocity field based on the campaign-type data, the research team will estimate an updated tectonic model of the present-day motions of the Nubia and Somalia plates. All available CGPS stations located on the defined stable part of these plates
will be used. This model will act as reference to compute the relative velocities of the campaign stations. An important result of the analysis of the relative motions will be the improvement of the understanding about the Nubia-Somalia plate boundary in the South-East Africa and the possible
identification of other tectonic blocks in this region. Finally, the experience of the research team on tsunamis studies enables the realization of an additional task that will be complementary to the
main line of research: the study of tsunamis on the Mozambican coast. The impact of an Indian Ocean mega-tsunami will be investigated using numerical ocean modeling. KINEMA will provide new insights in the present-day kinematics of South-East Africa. We aim to evaluate the present-day strain field and to delimitate better the plate boundaries, crucial to constrain more realistically the hazard scenarios for this region, in particular due to seismic and tsunami events.
   

 

 

 

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