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<p>On the 16th of September, 2021, a magnitude 6.0 earthquake occurred Luxian Country, Sichuan Province. This event re-ignited domestic and international interest in the underlying seismogenic processes and earthquake hazards within and around the Sichuan Basin. To better understand the subsurface strata and seismic activity conditions in this area, we conducted a detailed 3D reconstruction of P-wave velocity and Vp/Vs distributions using seismic tomography, based on seismic data obtained from a recently implemented dense sensor array network. Additionally, integrating 3D magnetotelluric data obtained through post-earthquake research, we analyzed relationships between velocity structure, seismicity, structural background, and earthquake risk in the Luxian. Results indicate significant lateral heterogeneity in the shallow P-wave velocity of the Luxian <i>M</i><sub>S</sub>6.0 earthquake and surrounding regions, with different segments of the Luoguanshan and Gufoshan anticlines showing distinct velocity anomalies. The epicenter of the mainshock is situated along the demarcation line that separates regions of high and low P-wave velocity disparities. On the northwestern flank of the Luxian region, at a depth of approximately 4 km, exhibits high Vp/Vs values, suggesting fluid presence that likely contributed to lateral Vp/Vs differences near the epicenter. Combining these findings with magnetotelluric data and surface geological surveys, we speculate that the Luxian <i>M</i><sub>S</sub>6.0 earthquake may have resulted from dislocation of pre-existing blind fault under regional tectonic stress and fluid influence.</p>

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Three-Dimensional Shallow P-wave Velocity Distribution in the Source Area of the 2021 MS6.0 Luxian Earthquake from Dense Array Seismic Imaging

  • 期刊论文

  • 发表日期：

    2025年5月30日

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  • Jian-xun Yang,
  • Qi-yan Yang,
  • Da-hu Li,
  • Yong-ming Lu,
  • Ping-ping Wu,
  • Hui-li Guo,
  • Ning-bo Jiang,
  • Mi Gao,
  • Heng Pan

摘要

On the 16th of September, 2021, a magnitude 6.0 earthquake occurred Luxian Country, Sichuan Province. This event re-ignited domestic and international interest in the underlying seismogenic processes and earthquake hazards within and around the Sichuan Basin. To better understand the subsurface strata and seismic activity conditions in this area, we conducted a detailed 3D reconstruction of P-wave velocity and Vp/Vs distributions using seismic tomography, based on seismic data obtained from a recently implemented dense sensor array network. Additionally, integrating 3D magnetotelluric data obtained through post-earthquake research, we analyzed relationships between velocity structure, seismicity, structural background, and earthquake risk in the Luxian. Results indicate significant lateral heterogeneity in the shallow P-wave velocity of the Luxian MS6.0 earthquake and surrounding regions, with different segments of the Luoguanshan and Gufoshan anticlines showing distinct velocity anomalies. The epicenter of the mainshock is situated along the demarcation line that separates regions of high and low P-wave velocity disparities. On the northwestern flank of the Luxian region, at a depth of approximately 4 km, exhibits high Vp/Vs values, suggesting fluid presence that likely contributed to lateral Vp/Vs differences near the epicenter. Combining these findings with magnetotelluric data and surface geological surveys, we speculate that the Luxian MS6.0 earthquake may have resulted from dislocation of pre-existing blind fault under regional tectonic stress and fluid influence.