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When the
largest seismic project ever undertaken in Africa takes place in a country
caught up yet again in famine, it not only raises a nightmarish logistics
operation, but also difficult ethical issues. University
of Leicester geophysicists recently led just such an operation in Ethiopia. Phase 3 of the EAGLE Project (Ethiopia Afar Geoscientific Lithospheric Experiment) has just been completed, under the leadership of Professor Peter Maguire. The project involves study of the first stages in the break-up of a continent, and in particular the transition from continental to oceanic rifting.
While
Phases 1 and 2 of the project recorded natural earthquakes, Phase 3 has
involved a controlled source seismic study involving the detonation of
explosive charges in deep boreholes on land and in lakes, recorded by
instruments deployed on two 450km long profiles,
along the axis and at right angles to the Ethiopian Rift.
The
instruments record the seismic waves as they reach the Earth’s surface, the
resulting seismograms being compiled into time-distance record sections, which
can then be interpreted to provide high-resolution images of the crust and
immediate upper mantle of the Earth. These
will show how much the Earth’s crust has stretched, the distribution of
sediments and volcanic rocks within the Rift, and, it is hoped, the location
of magma chambers beneath the profiles, sourcing the surface volcanics. Major
partners in the project include Stanford University and the University of
Texas, El Paso, USA, two of the most influential US universities in this
field, which made available funding of £300,000.
Other principal partners included the University of Leeds and Royal
Holloway College, London, (who respectively led Phase 1 and 2 of EAGLE), the
University of Copenhagen, the Dublin Institute of Advanced Studies and the
University of Vienna. Ethiopia
itself has been deeply committed to the project, with strong support from the
Ethiopian Commission of Science and Technology, and the involvement of highly
skilled scientists from the Geophysical Observatory and the Department of
Geology and Geophysics at the University of Addis Ababa, as well as from the
Ethiopian Geological Survey and the Petroleum Operations Department of the
Ethiopian Ministry of Mines. Phase
3 of the study required a huge and sometimes dangerous logistics programme
involving 70 scientists from the USA, Europe and Ethiopia, deploying 1,000
seismic recorders, transporting 22 tons of explosive in security-guarded
trucks, firing that explosive at 19 shotpoints in both deep boreholes and two
saline lakes, the whole project covering an area of 400 x 400 sq km of
Ethiopian countryside from the Blue Nile to the Bale Mountains and the Rift
Valley Lakes to Afar. In
the field were six shooting teams drawn from the US, UK, Austria, Denmark and
Ireland. Twenty recording teams were
responsible for the deployment and pick up of the seismic recorders.
Other personnel were based in the two centres of Nazret and Addis
Ababa, operating the computer equipment, the communication system and managing
the project. All teams included
European or US plus Ethiopian researchers. The
project also raised ethical issues. As
Ethiopia is once again caught up in famine, was it right that such a large
group of international scientists should “invade” the country, and so much
funding should be ploughed into a scientific research project? The
Ethiopian Government has been hugely supportive, pointing out the investment
and academic prestige EAGLE has brought to the country.
It is also certainly the case that there will be benefits to Ethiopia
in terms of developing knowledge of the seismic and volcanic hazard, the
mineral and geothermal resource, and of understanding the country’s geology. Equally,
however, the results will be of major importance to Earth Scientists the world
over, and will be published in international scientific journals and popular
literature.
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Last updated: 4 March 2003 10:55
Created by: Rachel Tunstall
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