Mapping Crustal Structure and Stress in the Kivu Rift from Bayesian Anisotropic Tomography

We present a probabilistic anisotropic P-wave tomographic study of the Kivu segment of the western East African Rift, incorporating local seismicity recorded by the Kivu Seismic Network. Using a Bayesian inversion approach, we map both isotropic velocity variations and directional anisotropy, providing robust estimates of uncertainties. Our results reveal broad low-velocity zones (~–2%) likely associated with magma-rich regions, and fast domains corresponding to rigid crustal blocks. South of the Virunga Volcanic Province (VVP), fast anisotropic planes are predominantly rift-perpendicular, while rift-parallel orientations dominate in distal regions, especially in the easternmost sector. Numerical modelling indicates that volcanic and topographic loading can explain rift-perpendicular anisotropy near the VVP, but not the patterns observed farther from volcanic edifices, suggesting a combined influence of regional extension, magmatic activity, and long-lived structural inheritance. These findings provide new insights into the interplay between crustal structure, tectonic stress, and magmatism, with implications for rift evolution and regional seismic and volcanic hazard assessment.