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<p>The epidemic-type aftershock sequence (ETAS) model is commonly used for seismic risk assessment and earthquake forecasting. It incorporates physically interpretable parameters that control the behavior of offsprings. Variability in these parameters suggests that earthquakes are driven by distinct mechanisms. Since these parameters vary with local geological factors and are not transferable across tectonic settings, region-specific calibration is essential. Currently, however, no ETAS parameter estimates exist for Africa, so seismic hazard assessments on the continent often rely on approximations rather than tailored approaches. To address this, we investigate ETAS parameters variability across Africa by dividing the continent into sub-regions and fitting the model to earthquakes in each subregion using the Davidon–Fletcher–Powell optimization algorithm. We then compare parameter estimates across sub-regions and examine potential correlations with physical properties of the Earth’s crust that are commonly thought to be the main driving factor in earthquake occurrence. Our results reveal complex regional variations in ETAS estimates. Parameters that describe productivity (<i>α</i>), temporal decay (<i>c</i>), and spatial distribution (<i>d</i>, <i>γ</i>) of aftershocks appear to be the most widely dispersed, probably due to missing events in the catalog caused by sparse seismic networks. Additionally, we observe correlations between certain parameters and geophysical properties of the crust, including a positive correlation between the parameter <i>p</i>, which represents the decay of aftershocks, and both heat flow and the compressional-to-shear-wave velocity ratio, and a negative correlation with Curie depth. An extreme value distribution analysis suggests a relatively high probability of a magnitude 7 or greater earthquake occurring in Northwest Africa and the western East African Rift System within the next decade, underscoring the need for measures that enhance public awareness and preparedness in these regions. Our results provide a preliminary set of ETAS parameters for Africa and can serve as a reference for implementing operational earthquake forecasting on the continent.</p> Graphical Abstract <p></p>

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Variability of ETAS parameters and their relationship with physical processes for earthquake forecasting in Africa

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年3月10日

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  • Thystere Matondo Bantidi,
  • Takeshi Nishimura,
  • Takeo Ishibe,
  • Bogdan Enescu,
  • Georges Mavonga Tuluka

摘要

The epidemic-type aftershock sequence (ETAS) model is commonly used for seismic risk assessment and earthquake forecasting. It incorporates physically interpretable parameters that control the behavior of offsprings. Variability in these parameters suggests that earthquakes are driven by distinct mechanisms. Since these parameters vary with local geological factors and are not transferable across tectonic settings, region-specific calibration is essential. Currently, however, no ETAS parameter estimates exist for Africa, so seismic hazard assessments on the continent often rely on approximations rather than tailored approaches. To address this, we investigate ETAS parameters variability across Africa by dividing the continent into sub-regions and fitting the model to earthquakes in each subregion using the Davidon–Fletcher–Powell optimization algorithm. We then compare parameter estimates across sub-regions and examine potential correlations with physical properties of the Earth’s crust that are commonly thought to be the main driving factor in earthquake occurrence. Our results reveal complex regional variations in ETAS estimates. Parameters that describe productivity (α), temporal decay (c), and spatial distribution (d, γ) of aftershocks appear to be the most widely dispersed, probably due to missing events in the catalog caused by sparse seismic networks. Additionally, we observe correlations between certain parameters and geophysical properties of the crust, including a positive correlation between the parameter p, which represents the decay of aftershocks, and both heat flow and the compressional-to-shear-wave velocity ratio, and a negative correlation with Curie depth. An extreme value distribution analysis suggests a relatively high probability of a magnitude 7 or greater earthquake occurring in Northwest Africa and the western East African Rift System within the next decade, underscoring the need for measures that enhance public awareness and preparedness in these regions. Our results provide a preliminary set of ETAS parameters for Africa and can serve as a reference for implementing operational earthquake forecasting on the continent.

Graphical Abstract