Department of Physics/Geology/Geophysics, Alex Ekwueme Federal University Ndufu Alike Ikwo, P.M.B. 1010, Abakaliki, Ebonyi State, Nigeria.
Environ Monit Assess. 2020 May 9;192(6):352. doi: 10.1007/s10661-020-08339-6.
Understanding the tectonics at active sites of recent seismic activities in Nigeria is fundamental towards disaster mitigation and emergency planning. We apply geophysical techniques of gravity and magnetic methods to investigate crustal depths, subsurface geologic faults and fractures, and the overall subsurface interaction at Mpape region and environs. Estimated depths to the bottom of magnetic crust (basal depths) range between 11.0 and 11.4 km at the Mpape region and decrease further southward towards Guabe town. This signifies the depth range of the active crust within the region. Comparative deeper basal depths (15.0-16.2 km) were obtained at locations farther from Mpape-Guabe towns at Nasarawa, Rubochi, and Fuka regions, showing a more stable region away from Mpape region. Computed Moho depths from gravity data show deeper depths at the Mpape region (~ 34.1 km) suggesting that the active crust exists in the upper crust. Two-dimensional modeling analysis along a profile taken across the Mpape region shows a conspicuous subsurface basement intrusion at the Mpape region with deep faults and fractures reaching depths of 7-14 km. Shallow basal depths at the Mpape region resulting from significant subsurface intrusion and concentrated subsurface faults at the intruded region may be responsible for the instability of the Mpape region. The most affected area is located within the Mpape-Guabe towns. We recommend the establishment of seismic monitoring facilities in this area for effective monitoring and evaluation.
了解尼日利亚近期地震活动活跃区的构造情况，对于减轻灾害和应急规划至关重要。我们应用重力和磁力方法等地球物理技术，调查地壳深度、地下地质断层和裂缝，以及 Mpape 地区及其周边的整体地下相互作用。在 Mpape 地区，估算的磁性地壳底部深度（基底深度）在 11.0 到 11.4 公里之间，向南在 Guabe 镇逐渐减小。这标志着该区域活动地壳的深度范围。在距离 Mpape-Guabe 镇更远的 Nasarawa、Rubochi 和 Fuka 地区，获得了更深的基底深度（15.0-16.2 公里），表明这些地区更远离 Mpape 地区，地壳更为稳定。从重力数据计算得出的莫霍面深度显示，Mpape 地区的深度更深（约 34.1 公里），表明活动地壳存在于上地壳中。沿穿过 Mpape 地区的剖面进行的二维建模分析显示，在 Mpape 地区存在明显的地下基底侵入，深断层和裂缝延伸至 7-14 公里深处。Mpape 地区浅的基底深度是由于地下侵入和侵入区域集中的地下断层造成的，这可能是 Mpape 地区不稳定的原因。受影响最严重的地区位于 Mpape-Guabe 镇内。我们建议在该地区建立地震监测设施，以便进行有效监测和评估。
