Impact of Seismic Attenuation Corrections on Source Parameter Estimation

We estimate the stress drop ∆σ for 551 earthquakes from the 2019 Ridgecrest sequence in Southern California using a spectral decomposition. To assess the impact of propagation model assumptions, we apply a 2D cell-based approach that accounts for lateral attenuation variations and compare results with previous models using distance and depth-dependent attenuation. The 95% confidence interval for azimuthal-dependent attenuation over an 80 km radius is 0.290 at 2 Hz and 0.473 at 14 Hz (log10 units). While the 2D model reveals significant azimuthal variations, the overall ∆σ distribution remains similar to that from a simple distance-dependent model, at least for the analyzed data set. High ∆σ is observed near the M7.1 and M6.4 events, while lower values appear at shallower depths, especially toward the Coso region and near the left-lateral fault junction of the M6.4 sequence. All models consistently identify a high-∆σ region at 4-8 km depth between stations CLC and WRC2, north of the M7.1 hypocenter, where the main fault bends. While spatial comparisons reveal more localized differences, the most pronounced impact arises when the attenuation model incorporates depth dependence.