Strain rate field on the Nigeria lithosphere derived from GNSS velocity
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ORIGINAL PAPER
Strain rate field on the Nigeria lithosphere derived from GNSS velocity Swafiyudeen Bawa 1
&
Lazarus Mustapha Ojigi 1 & Joseph Danasabe Dodo 2 & Kola Muideen Lawal 3
Received: 5 March 2020 / Accepted: 25 August 2020 # Società Italiana di Fotogrammetria e Topografia (SIFET) 2020
Abstract The Global Navigation Satellite System (GNSS) over the years has become an essential instrument in modelling geodynamic processes, because of its high spatio-temporal characteristics. Accurate velocity modelling of GNSS stations and strain rate analysis can provide an accurate mechanism for studying the deformation of the earth crust. Therefore, this study presents the strain rate tensor of the Nigeria crust from GNSS network, but first, the GAMIT/GLOBK was used to process and obtain accurate velocity solution of the Nigerian Permanent GNSS Network (NigNET). The surface deformation of Nigeria deduced from strain analysis was computed using splines in tension. The results revealed that the highest extensional and compressional strain rates of up to 2.67 to 2.89μstrain/year were observed around parts of the north-west (Jigawa, Kaduna and Kano) and north central region (parts Abuja and Jos) and some parts of the north-east (parts of Bauchi and Gombe), while the lowest minimal or low extensional and compressional strain rates of 0.09 to 0.534μstrain/year were observed around some parts of the north central (parts of Kwara and Niger) and parts of north-west (parts of Kebbi, Zamfara and Sokoto). The highest maximum shear strain rate of about 0.4μstrain/year which has its peak around some parts of Kaduna, Abuja, Plateau and Bauchi was observed. The highest areal dilatation rate observed in Nigeria is about 1.02μstrain/year. The study serves as a benchmark for further studies. Keywords GNSS . Nigeria . NigNET . Strain rate
Introduction Nigeria (Fig. 1) is situated on the eastern flank of the Atlantic Ocean margin which is part of the Nubia plate. This region is believed to be tectonically inactive and thus seismically dormant. Overtime, the south-western part of the country has felt vibrations, with no losses of lives reported (Akpan and Yakubu 2010). In September 2016, a micro-event (earth tremor) was experienced at Koi and Jaba area, and another was felt in 2018 at Maitama and Mpape area, district of Abuja (Federal capital Territory) (Afegbua et al. 2019). So far, the tectonic and
* Swafiyudeen Bawa [email protected] 1
Department of Geomatics, Ahmadu Bello University, Zaria, Kaduna, Nigeria
2
Centre for Geodesy and Geodynamics, NASRDA, Toro, Bauchi, Nigeria
3
Department of Physics, Ahmadu Bello University, Zaria, Kaduna, Nigeria
present geodynamic activities in Nigeria have been reviewed and studied from a seismotectonic perspective (see Afegbua et al. (2011, 2019), Tsalha et al. (2015) and Oluwafemi et al. (2018a, b, c)). Although causes of these tremors are still clearly not understood in the region, some of them have been attributed to the effects of distant earthquakes (Olugboji et al. 2020). Over the
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