Variation of Earthquake Focal Depth in Parts of Oceanic Ridges

This study was conducted to evaluate the variation of earthquake focal depth in parts of Oceanic Ridges. The data set for this work were extracted from the International Seismological Centre (ISC), Pipers Lane, Thatcham, Berkshire, United Kingdom. The selected data consisted of earthquakes with Mb≥4.0 for the study area from 1st January 1901 to 31st December 2015 (115years) with focal depth from 0 – 400 km. A total of 10,801 events were employed in the study with Chile Ridge having 1574, Mid-Atlantic Ridge 4924 and Pacific Ridge 4303. The result of this study revealed that in all locations, earthquake events concentrate in the depth range 0-50 km which falls within the shallow-focus earthquakes. In Pacific Ridge, the number of events was decreasing with increasing focal depth. It was also found that the earthquake events are highest in Mid - Atlantic Ridge (46%) as compared to Chile Ridge (14%) and Pacific Ridges (40%). The indication of this is that the processes accompanying seismicity which include the rate of tectonic divergence of oceanic plates, crustal and sub-crustal stress accumulations are widespread in Mid - Atlantic ridge. Hence the Atlantic Ocean is vulnerable to tsunamigenic earth dangers.