The Abuja earth tremors and geological surveys (I)
Earthquakes are the result of sudden movement along faults within the Earth. The movement releases stored-up ‘elastic strain’ energy in the form of seismic waves, which propagate through the Earth and cause the ground surface to shake. Meanwhile, explanation of the origins of earthquake would not be complete without mentioning the phenomenon of plate tectonics […]
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Earthquakes are the result of sudden movement along faults within the Earth. The movement releases stored-up ‘elastic strain’ energy in the form of seismic waves, which propagate through the Earth and cause the ground surface to shake. Meanwhile, explanation of the origins of earthquake would not be complete without mentioning the phenomenon of plate tectonics and continental drift.
A simple definition of earth tremor is a slight earthquake. And the incidences of ground being shaken in the manner experienced around the hilly Mpape area located at the North-East of Abuja city could not be removed from being an earth tremor. What it means is that, a slight earthquake is being experienced. The earlier we accept the fact, identify the possible triggers and embrace mitigation measures the better.
Meanwhile, another fact from all known literature, is that Nigeria has never been mentioned to belong to any of the earthquake or volcanic zones of the world. Simply because it is not located along, or close to the boundary of any of the oceanic or continental plates.
From my university Geology lessons, I was taught that the earth’s outermost layer is fragmented into about 15 major slabs called tectonic plates. Plate tectonics means the gradual movement of continental and oceanic plates. From literature explanations, most earthquakes are associated with tectonic plate boundaries and the theory of plate tectonics can be used to provide a simplified explanation of the global distribution of earthquakes.
It is also known that the interior of the earth is made up of unstable liquid substance called molten magma. The renowned high mountain ranges, which dimensions go roughly one mile to ten miles, are folds in the earth. And they function as stakes akin to ones used to anchor a tent to the ground, in order to stabilise the surface. Otherwise, it behaves as a ship rocking in the sea.
In the wake of the latest seismic activities, which occurred from September 13 to 17, 2024, the Nigeria Geological Survey Agency released a statement that the tremors recorded were low and posed no threat to the community. However, before the recent incidence, it had occurred from September 5 to 7, 2018, exactly six years earlier. In the light of the prevailing occurrences, many questions should be generated, which would certainly require credible and scientific explanation.
The Geological Agency would have to provide more explanations than the usual ‘no threat’ statements. Otherwise, people, specifically the affected community that continuously experience the dangerous phenomena, will gradually lose confidence in their explanations.
The physiographic map of the FCT presented in the Abuja Master Plan was interpreted from Nigerian Federal Surveys and U.S. Geological Survey in 1977. Some of the geological details for the site of the new capital were not available for the master plan preparation, as stated in the relevant chapter. However, four major areas were identified for the interpretation. They include river basins, erosional plains, dissected zone and hills, including tectonic hills. The Mpape area where the tremors occur is a high-spot overlooking the city, geologically termed a folded area, and constitutes dissected zone with granite, laterite hills, and tectonic ridges.
The Gwagwa plains chosen as the best location for the New Federal Capital City by the International Planning Associates (IPA), is entirely surrounded by mountain ranges. To the North and North-East, the Outer Northern Expressway (ONEX) separates the city and the very conspicuous Bwari-Aso hills. It continues on a stretch to the Zuma Hills monument area, centered on Zuma Rock, one of the distinctive and easily recognised inselberg on the FCT boundary with Niger State. To the South and South-East, the city is separated from the Karu-Agwai escarpments by the Outer Southern Expressway (OSEX).
No doubt, the city planners must have recognised the stabilising function of the mountain ranges by earmarking the areas for preservation. It is very clear that the salient functions performed by these mountain ranges are not recognised or comprehended. Presently, most of the areas around the mountainous grounds are where quarries and mines were established, with frequent rock blasting. They were also colonised by land grabbers and riddled with many legal and illegal land use violations and land reclamations.
Truly, not only Abuja, there is no place in the entire nation that has ever been mentioned to be an earthquake zone. At the same time, we haven’t encountered any literature that ever mentioned that earth tremor or quake, cannot occur in hinterlands away from continental or oceanic plate boundaries. Or, cannot be triggered by other procedures.
Our concern is the violations of the Master plan’s development regulations, as recommended by the IPA, that the natural state of the mountainous areas are to be preserved. There is also need for further explanation to the occurrence of the tectonic ridges along this axis, what are the implications and mitigations to any of their adverse effects.
To be continued