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<p>The occurrence of the 7.3 magnitude Sarpol-e Zahab earthquake on November 12, 2017, in the Zagros region underscored the importance of conducting a comprehensive seismicity analysis in this area. In this study, we have analyzed the spatiotemporal variation of the seismic <i>b</i>-value and <i>D</i><sub>C</sub>-value in the vicinity of the Sarpol-e Zahab earthquake and surrounding region using a unified and homogeneous earthquake catalog spanning 01/01/2006–10/31/2024 belong to the Iranian Seismological Center (IRSC). In the tectonically active parts of the study area, <i>b</i>-values range from 0.4 to 1.4. According to the results, prior to the mainshock, the <i>b</i>-value exhibited low values in the vicinity of the Sarpol-e Zahab earthquake, suggesting significant stress accumulation and an imminent rupture. In contrast, the <i>D</i><sub>C</sub>-value displayed higher values, indicating increased fault heterogeneity and crack complexity as the fault approached failure. Immediately after the mainshock, the <i>b</i>-value increased sharply, corresponding to stress release and a dominance of smaller aftershocks, whereas, the <i>D</i><sub>C</sub>-value decreased. The temporal <i>b</i>-value curve shows a decreasing trend before the occurrence of the November 12, 2017, Mw 7.3 earthquake. Temporal analysis of the <i>b</i>-value also reveals a clear increase post-mainshock, indicating stress redistribution and ongoing fault healing. The concentration of low <i>b</i>-values (<i>b</i> &lt; 0.5) between 10 and 20&#xa0;km depth suggests a potential for stress concentration in this depth range. These findings demonstrate the complementary roles of <i>b</i>-value and <i>D</i><sub>C</sub>-value in characterizing seismic behavior and fault evolution. In the tectonically active regions of the study area, which correlate to the reverse/thrust and strike-slip active faults, the <i>b</i>-values and <i>D</i><sub>C</sub>-values range from 0.4 to 1.4 and from 1.5 to 4, respectively. The observed patterns provide valuable insights into pre-seismic stress buildup, post-seismic stress relaxation, and faulting processes.</p>

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Spatial–temporal variations of b-value and DC-value prior to the November 12, 2017, Mw 7.3 earthquake in Sarpol-e Zahab, Zagros, Iran

  • 期刊论文

  • 发表日期：

    2025年5月30日

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  • Muhammed Hossein Mousavi,
  • Amir Talebi,
  • Faegheh Mina Araghi,
  • Malihe Maqouli

摘要

The occurrence of the 7.3 magnitude Sarpol-e Zahab earthquake on November 12, 2017, in the Zagros region underscored the importance of conducting a comprehensive seismicity analysis in this area. In this study, we have analyzed the spatiotemporal variation of the seismic b-value and DC-value in the vicinity of the Sarpol-e Zahab earthquake and surrounding region using a unified and homogeneous earthquake catalog spanning 01/01/2006–10/31/2024 belong to the Iranian Seismological Center (IRSC). In the tectonically active parts of the study area, b-values range from 0.4 to 1.4. According to the results, prior to the mainshock, the b-value exhibited low values in the vicinity of the Sarpol-e Zahab earthquake, suggesting significant stress accumulation and an imminent rupture. In contrast, the DC-value displayed higher values, indicating increased fault heterogeneity and crack complexity as the fault approached failure. Immediately after the mainshock, the b-value increased sharply, corresponding to stress release and a dominance of smaller aftershocks, whereas, the DC-value decreased. The temporal b-value curve shows a decreasing trend before the occurrence of the November 12, 2017, Mw 7.3 earthquake. Temporal analysis of the b-value also reveals a clear increase post-mainshock, indicating stress redistribution and ongoing fault healing. The concentration of low b-values (b < 0.5) between 10 and 20 km depth suggests a potential for stress concentration in this depth range. These findings demonstrate the complementary roles of b-value and DC-value in characterizing seismic behavior and fault evolution. In the tectonically active regions of the study area, which correlate to the reverse/thrust and strike-slip active faults, the b-values and DC-values range from 0.4 to 1.4 and from 1.5 to 4, respectively. The observed patterns provide valuable insights into pre-seismic stress buildup, post-seismic stress relaxation, and faulting processes.