Geophysical Evaluation of Central Nigeria Earth Tremor Activities using High Resolution Airborne Magnetic Data

Abstract

The aim of this study is to investigate the actual causes of earth tremors in Central Nigeria using geophysical technique. Since 1933 till date (over 88 years), small to moderate magnitude earthquakes have either been observed or instrumentally recorded in Nigeria. However, the specific causes of the intra plate earthquakes in Nigeria is still not well known. In this study therefore, a high-resolution aeromagnetic data analysis was performed to evaluate the various theories proposed as the causes of tremor activity in central Nigeria with a view to ascertaining the actual causes of earthquakes in the West African country that lies on a stable crust. The total magnetic intensity data acquired from the Nigerian Geological Survey Agency (NGSA) in the Central Basement complex of Nigeria, was processed and filtered using the tilt derivative, lineament analysis, and advanced Analytic Signal- Hilbert Solution filter. To define the trends of both major and minor structure, a lineament plot was extracted and plotted. The analysis revealed a dominant NE-SW and NW-SE trending structure that is distributed throughout the study area. The regional North Atlantic Romanche fault system, which extends from the offshore (Niger Delta) into the continental crust, was mapped and is thought to extend from Gwagwalada in the study area's south, through Gwarinpa and Mpape, to Kwoi, and beyond Kafanchan.Findings from our study have indicated that, areas prone to Earth tremors are linked to the Romanche fault by numerous NE-SW and NW-SE faults that act as conduits for seismic energy that causes tremor. Using lineament density analysis, tremor active areas have been interpreted to be highly deformed; thus, seismic energy induced into the environment would result in tremors. This study demonstrates that the regional North Atlantic Romanche fault system is the primary source of seismic energy that causes the earth tremors in central Nigeria.