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<p>Based on the observational data from 60 short-period stations deployed in the Jishishan M6.2 earthquake epicenter and adjacent regions (Gansu Province, 2023), this study inverted the near-surface S-wave velocity structure through teleseismic receiver function analysis by using the amplitude of direct P-wave. The results reveal that the epicentral area (Liugou Township and surroundings) exhibits markedly low S-wave velocities of 400-600 m/s, with a mean value of (500 ± 50) m/s. In contrast, intermountain basins—Guanting Basin and Dahejia Basin—demonstrate significantly elevated velocities, exceeding the epicentral zone by 100–300 m/s, with values concentrated at 600–900 m/s. Notably, localized areas such as Jintian Village and Caotan Village maintain stable S-wave velocities of (700 ± 30) m/s.The western margin tectonic belt of Jishishan displays distinctive velocity diff erentiation: A pronounced velocity gradient zone along the 35.8°N latitude boundary separates northern areas (&lt;550 m/s) from southern regions (&gt;750 m/s). These findings demonstrate significant spatial heterogeneity in shallow S-wave velocity structures, primarily controlled by three factors: (1) topographic-geomorphic units, (2) stratigraphic lithological contrasts, and (3) anthropogenic modifications. The persistent low-velocity anomalies (&lt;600 m/s) in the epicentral zone and northern Yellow River T2 terrace likely correlate with Quaternary unconsolidated sediments, enhanced groundwater circulation, and bedrock weathering.These results provide critical geophysical constraints for understanding both the seismogenic environment of the Jishishan earthquake and its damage distribution patterns. Furthermore, they establish a foundational framework for regional seismic intensity evaluation, site amplification analysis, and secondary hazard risk assessment.</p>

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Investigation of Near-Surface S-Wave Velocity Structure beneath the Epicenter and adjacent Area of the Jishishan Earthquake by using the Receiver Function

  • 期刊论文

  • 发表日期：

    2025年6月4日

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  • Fan-chang Meng,
  • Ruo-ge Xu,
  • Hui Sun,
  • Bo Li,
  • Yun Long

摘要

Based on the observational data from 60 short-period stations deployed in the Jishishan M6.2 earthquake epicenter and adjacent regions (Gansu Province, 2023), this study inverted the near-surface S-wave velocity structure through teleseismic receiver function analysis by using the amplitude of direct P-wave. The results reveal that the epicentral area (Liugou Township and surroundings) exhibits markedly low S-wave velocities of 400-600 m/s, with a mean value of (500 ± 50) m/s. In contrast, intermountain basins—Guanting Basin and Dahejia Basin—demonstrate significantly elevated velocities, exceeding the epicentral zone by 100–300 m/s, with values concentrated at 600–900 m/s. Notably, localized areas such as Jintian Village and Caotan Village maintain stable S-wave velocities of (700 ± 30) m/s.The western margin tectonic belt of Jishishan displays distinctive velocity diff erentiation: A pronounced velocity gradient zone along the 35.8°N latitude boundary separates northern areas (<550 m/s) from southern regions (>750 m/s). These findings demonstrate significant spatial heterogeneity in shallow S-wave velocity structures, primarily controlled by three factors: (1) topographic-geomorphic units, (2) stratigraphic lithological contrasts, and (3) anthropogenic modifications. The persistent low-velocity anomalies (<600 m/s) in the epicentral zone and northern Yellow River T2 terrace likely correlate with Quaternary unconsolidated sediments, enhanced groundwater circulation, and bedrock weathering.These results provide critical geophysical constraints for understanding both the seismogenic environment of the Jishishan earthquake and its damage distribution patterns. Furthermore, they establish a foundational framework for regional seismic intensity evaluation, site amplification analysis, and secondary hazard risk assessment.