The present research examines the spatio-temporal variations of the b-value and DC-value parameters in the vicinity of the 7.3 magnitude Sarpol Zahab earthquake (11 November 2017). The data used in this study were extracted from an integrated catalogue maintained by the Iranian Seismological Center (IRSC) covering the period from 1 January 2006 to 31 October 2024. The primary objective is to achieve a deeper understanding of the stress redistribution processes within the geological structure of the Zagros region and to evaluate the potential of using the b-value and DC-value as warning indicators for forecasting the occurrence of significant seismic events.
In tectonically active regions, statistical analyses have shown that the b-value can vary between 0.4 and 1.4. A marked reduction in the b-value near fault zones prior to the main shock indicates an increasing accumulation of stress and the potential imminence of rupture. Conversely, the observed increase in the DC-value reflects structural heterogeneity and the complexity of the fault-breakage mechanism as the stress threshold is approached. Immediately following the main event, a significant increase in the b-value accompanied by a decrease in the DC-value was observed, which may be interpreted as the result of a sudden stress release via ensuing microearthquakes.
Temporal analyses reveal that the pre-seismic decrease in the b-value and its subsequent post-seismic increase clearly illustrate the redistribution of stress within the region’s geological framework. Moreover, an in-depth investigation of vertical variations shows the presence of extremely low b-values (less than 0.5) at depths between 10 and 20 kilometers. This finding serves as an important indicator of stress concentration at these depths and could play a decisive role in future seismic risk assessments.
The results underscore the significance of simultaneously utilizing the b-value and DC-value parameters in seismic analysis. In tectonically active areas, the concurrent variations of these two parameters not only identify the prevailing stress regime but also effectively reflect the evolution of fault systems and tectonic processes associated with reverse, strike-slip, and extensional faults. This study demonstrates that a persistent decrease in the b-value coupled with an increase in the DC-value during the pre-seismic phase may serve as an early warning signal of stress accumulation and structural heterogeneity along faults, whereas the reversal of this pattern in the post-seismic phase indicates a release of stress.
In conclusion, by leveraging the variations in the b-value and DC-value parameters, the present research not only provides a detailed analysis of the current state of lithospheric stress but also offers novel insights into earthquake prediction and the management of related risks. These findings can serve as a basis for developing preventive strategies and enhancing modern monitoring systems in regions characterized by high tectonic activity. Future studies focusing on the interrelationship of these parameters in other tectonically active areas are expected to further enrich our understanding of faulting processes and improve the precision of seismic predictions.