Abstract
ESTIMATION OF RETURN PERIODS AND EARTHQUAKE OCCURRENCE RISK IN SOME OCEANIC RIDGES USING POISSON’S MODEL
*Abong A. A., Kanu M. O., Ulem E. B. and Ogbebe J. U.
ABSTRACT
This study estimated return periods and earthquake occurrence risk in some Oceanic Ridges using Poisson?s model. A 115-year earthquake data from 1st January 1901 to 31st December 2015 were extracted from the earthquake catalogue, International Seismological Centre, Pipers Lane, Thatcham, Berkshire, United Kingdom. The selected data consisted of earthquakes with magnitude Mb?4.0 with focal depth of 0-700km. A total of 8,932 events were employed in the study with Chile Ridge having 1440, Mid-Atlantic Ridge 4564 and Pacific Ridge 2928. The findings of this study revealed that in Chile Ridge the occurrence possibility of an earthquake with magnitude Mb?8.0 within 10 years is 0.2505 and 100 years is 0.9441 with return period of 34.67 years. Similarly, in Mid-Atlantic Ridge the occurrence possibility of an earthquake with magnitude Mb?8.0 within 10 years is 0.6828 and 100 years is 1.0000 with return period of 8.71 years. For Pacific Ridge, the occurrence possibility of an earthquake with magnitude Mb?8.0 within 10 years is 0.6152 and 100 years is 0.9999 with return period of 10.47 years. It was also observed that as the earthquake magnitudes are increasing, the corresponding earthquakes risks are decreasing. It is found that Chile Ridge has a higher return period for earthquake of magnitude 8.0 compared to Mid-Atlantic Ridge and Pacific Ridge. But earthquake occurrence cannot be predicted with certainty because the concept of earthquake prediction is still a complicated issue due tosaturation of earthquake magnitudes and variation of data collection by different seismic stations and networks
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