Characteristics of Earthquakes along the East African rift and the Mid-Atlantic ridge

ABSTRACT

Three hundred and thirty earthquakes data sets within a period of twenty-six years (1990 -2016) were obtained for the Mid-Atlantic Ridge and East African Rift. The data were analyzed using Seismic Analysis software (SEISAN 9.0) and Microsoft Excel, and the results showed that the earthquakes occur more at a focal depth of 10 km. The body wave magnitude for EAR ranged between 4.1 to 6.6 with a dominant magnitude range of 4.5 – 4.9 and 5.0 – 5.4 having 53 and 52 (32%) occurrences respectively. m_b for MAR ranged from 4.1 to 6.4 and recorded a dominant magnitude range of 4.5 – 4.9 and 68 (41%) occurrences. Surface wave magnitudes for EAR and MAR ranged from 4 to 7.2 and 4.1 to 7 respectively while their dominant Ms range was 4.5 – 4.9 with 18 (28%) and 26 (34%) occurrences respectively. Moment magnitude for EAR and MAR ranged from 4.7 to 7.1 and 4.9 to 6.8 respectively while their dominant range was 5.0 – 5.4 with 29 (45%) and 37 (49%) occurrences respectively. Monthly time occurrence showed that EAR had more earthquakes occurring in March while MAR recorded highest occurrence in August. Empirical relationship between correlated magnitudes for EAR and MAR were obtained. The b-values for EAR and MAR were 0.77 and 0.83 respectively while stress drop values within these regions ranged from 2.2 – 51.1 bar, with an observed radius of rupture between 7.0 – 14.4 cm.