Stress and Strain evolution of the 2023 Jajarkot Earthquake from Coulomb Stress Transfer Modeling 

This study examines the stress and strain evolution of the 2023 Mw 5.7 Jajarkot earthquake using spectral source analysis and Coulomb stress transfer modeling. Corner frequency was estimated by waveforms recorded at regional stations  and seismic moment was obtained using the Brune ω⁻² model. Slip was then calculated from D=M₀/(μA)). We estimated fault length (L) and width (W) using the Wells & Coppersmith (1994) empirical scaling relations for reverse faults such that the predicted dimensions are L ≈ 7.7, km and W ≈ 5. 3 km. Coulomb stress changes were computed using Okada’s elastic dislocation theory, separating shear and normal stress contributions to evaluate ΔCFS=Δτ+ μ′ Δσ_n .  A strong linear scaling (R² = 1.00) between slip and maximum ΔCFS indicates that stress evolution is primarily slip-controlled, with typical thrust-fault patterns of positive stress loading in the hanging wall and stress shadows in the footwall. Variations among stations reflect radiation effects, path attenuation, and minor rupture heterogeneity. Analytical tools such as ObsPy, NumPy, and custom Python stress-mapping routines were used to visualize ΔCFS fields. The results highlight significant shallow stress concentration and provide insight into the fault geometry and stress redistribution within the Western Nepal Seismic Gap.

Key words: Thrust Fault, Coulomb transfer, radiation pattern, Central Himalaya region , Stress shadow