Investigating Possible Fault Lines Responsible For the September 2016 Earth Tremor at Kwoi, Nigeria, Using Aeromagnetic Data

This research was aimed at investigating possible fault lines responsible for the September 2016 earth tremor at Kwoi, Nigeria using aeromagnetic data. Four aeromagnetic maps were acquired from the Nigerian Geological Survey Agency (NGSA), Abuja. These sheets include; sheets 166 (Anfu), 167 (Kachia), 187 (Kagarko) and 188 (Jemaa). The sheets then put together extend from 9 0 00’N - 10 0 00’N and from 7 0 30’ E - 8 0 30’ E covering the study area and its environs. Most of the anomalies trend NE – SW directions. The regional magnetic field data was separated from the residual magnetic data using the polynomial fitting method. The residual magnetic field image map revealed some subtle lineaments within the study area including region around epicenters.  The upward continued data of 150m gives a clearer view of the magnetic anomalies as the noise arising from the high frequency anomalies is suppressed. The shaded relief map of the upward continue data revealed some lineation close to the epicenters. Some lineaments observed on the Analytic signal map align with major fault/fracture on the geologic map especially south of Kwoi. Some Werner solutions generated intercept with some observed lineaments in the study area and no solution was generated on any of the epicenters. Euler solutions were generated around two of the epicenters. The depth range of the Euler solutions around the two epicenters is 1.2 km – 3.0 km. Cluster of Euler solutions around the epicenters trend along NW-SE and EW aligning with trend of the lineament on the Analytic signal and first vertical derivative maps.