Role of Lithospheric and Upper-Mantle Heterogeneities in Controlling Intraplate Seismicity in Central and Southeastern Brazil

Sumit Singh, Dip Ghosh

Seismicity in Central and Southeastern Brazil is spatially heterogeneous, with active zones showing little correspondence to major geological provinces, a pattern typical of many intraplate settings worldwide. While previous studies have explored possible controls using geophysical observations, the relative roles of crustal and upper-mantle heterogeneities in shaping the regional stress fields remain poorly constrained using large-scale calculations. We use, three-dimensional thermo-mechanical numerical models integrating lithospheric and mantle heterogeneities with regional stress conditions to investigate the intraplate seismicity in this region. A crustal seismic velocity model is employed to estimate crustal thickness and density, while seismic velocity anomalies from regional upper-mantle tomography are converted into a temperature field, from which density variations, lithospheric thickness, and rheology are derived. These crustal and mantle heterogeneities are incorporated into numerical models along with far-field east–west compressional stresses. Crustal density and thickness variations are also constrained using Gravitational Potential Energy and Crustal thickness gradients. Models with tomography-based thermal structures with far-field stresses produce localized lithospheric thinning and elevated strain rates that spatially correlate with seismicity. Regions of concentrated seismicity consistently coincide with zones of thinned lithosphere, enhanced strain rate, and positive correlations with gravitational potential energy and crustal thickness gradients. The results indicate that intraplate seismicity in central and southeastern Brazil is controlled by the combined effects of upper-mantle temperature heterogeneity, regional stress, and crustal-scale structural variations. These findings highlight the importance of coupling mantle dynamics with lithospheric and crustal structure to explain earthquake occurrence in intraplate regions.