[SSS07-P04] Recent Advances in Earthquakes Relocation and Probabilistic Seismic Hazard Assessment for Risk Mitigation and Planning in West Africa
キーワード：West Africa, Earthquakes relocation, Seismicity, PSHA, earthquakes forecast, planning
This work is aimed at utilizing modern techniques to improve earthquakes location and establish seismic hazard parameters for planning in West Africa. Over the years, dearth of data and well-defined velocity models have hindered robust seismological researches in the region. For the first time therefore, Regional Seismic Travel Times and iloc in Geotool software were used to relocate significant earthquakes; and Probabilistic Seismic Hazard Assessment was carried out using earthquake catalogue (1618-2018), with different levels of magnitude completeness determined for the sub-catalogues. The results showed enhanced events characterization and epicenters with attendant improved seismicity scenario. Maps of b-values, earthquakes density and that for updated seismicity have been produced for West Africa from this study. The regional maximum possible magnitude is estimated to fall in the range of [6.62; 7.17]. The b-value and activity rate were computed as 0.71±0.2 and 3.44±0.17 respectively. A forecast of future earthquakes occurrence shows that a magnitude 6.80 is likely to occur in West Africa approximately every 370 years. The Probabilities of the same event occurring annually and once in 50, 100 and 1000 years are 0.27%, 12.59%, 23.50% and 91.8% respectively. The annual probability of occurrence of small magnitude earthquakes (less than 5.0) is high. The 10% probability of exceedance of PGAs in 50 years ranged from 0.05 m/s² to 0.34 m/s². The significant hazard levels were observed in South Western Cameroon, South-Western Nigeria, Southern parts of Ghana, Eastern parts of Benin Republic, Guinea, Togo, Guinea Bissau, The Gambia, and Sierra Leone respectively.