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<p>The spatiotemporal heterogeneity of <span class="inline-formula"><i>b</i></span> values has great potential for helping in understanding the seismogenic process and assessing seismic hazard. However, there is still much controversy about whether it exists or not, and an important reason is that the choice of subjective parameters has eroded the foundations of much research. To overcome this problem, we used a recently developed non-parametric method based on a data-driven concept to calculate <span class="inline-formula"><i>b</i></span> values. The major steps of this method include (1) performing a large number of Voronoi tessellations and Bayesian information criterion (BIC) value calculation, selecting the optimal models for the study area, and (2) using the ensemble median (<span class="inline-formula"><i>Q</i>₂</span>) and median absolute deviation (MAD) value to represent the final <span class="inline-formula"><i>b</i></span> value and its uncertainty. We investigated spatiotemporal variations in <span class="inline-formula"><i>b</i></span> values before and after the 2019 Changning <span class="inline-formula"><i>M</i>_S=6.0</span> earthquake in the Sichuan Basin, China. The results reveal a spatial volume with low pre-mainshock <span class="inline-formula"><i>b</i></span> values near the mainshock source region, and its size corresponds roughly with the rupture area of the mainshock. The anomalously high pre-mainshock <span class="inline-formula"><i>b</i></span> values distributed in the NW direction of the epicenter were interpreted to be related to fluid invasion. The decreases in <span class="inline-formula"><i>b</i></span> values during the aftershock sequence along with the occurrences of several strong aftershocks imply that <span class="inline-formula"><i>b</i></span> values could be an indicator of the stress state. In addition, we found that although the distribution characteristics of <span class="inline-formula"><i>b</i></span> values obtained from different methods of investigation are qualitatively consistent, they differ significantly in terms of their specific values, suggesting that the best way to study the heterogeneous pattern of <span class="inline-formula"><i>b</i></span> values is in the joint dimension of space-time rather than separately in time and space. Overall, our study emphasizes the importance of <span class="inline-formula"><i>b</i></span>-value studies in assessing earthquake hazards.</p>