Probabilistic insights into seismic activation and quiescence across the East African rift system: Bayesian constraints on continental extension dynamics

Abstract

The East African Rift System (EARS) is the most active continental rift zone, where deformation is accommodated through a combination of faulting, magmatic processes, and aseismic deformation. However, the statistical characteristics of seismicity and their implications for stress evolution in rift environments remain less well constrained. In this study, we apply a Bayesian statistical framework to characterize the spatial and temporal variability of seismicity across the EARS using a declustered earthquake catalog from 1960 to 2025. Cluster-specific completeness magnitudes (Mc) are estimated using the Entire Magnitude Range (EMR) approach, and b-values are inferred within a Bayesian framework with explicit uncertainty quantification. Temporal variations in seismicity rate are assessed using z-value analysis. The results show consistently high b-values (1.20–1.40) and statistically insignificant z-value fluctuations (|z| < 3), indicating limited spatial and temporal variability in seismicity patterns. These observations point to a deformation regime dominated by distributed strain release and relatively low stress accumulation. This behavior contrasts with subduction systems, where seismicity is typically characterized by pronounced stress accumulation and release cycles, highlighting fundamental differences in tectonic processes. The overall pattern is consistent with a relatively stable extensional regime, although the underlying physical mechanisms cannot be fully resolved from seismicity data alone. The proposed framework demonstrates the value of Bayesian inference for quantifying uncertainty in seismic parameters and provides a transferable approach for comparative seismotectonic analysis in other tectonic settings.

Access to Document

Other files and links

• Link to publication in Scopus
• Open Access Version Available

Fingerprint