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<p>The Gunsan Basin in the South Yellow Sea has undergone multi-phase tectonic evolution in the East Asian margin, and its basin structures are important for understanding the regional tectonic processes. Previous studies using ocean-bottom seismometer (OBS) and streamer data have revealed a complex crustal structure in this region, including the crustal thinning due to strike-slip faulting and the development of buried hills. However, the large station spacing in OBS surveys results in low resolution of tomographic inversion, leading to an ambiguity in the interpretation of basin geometry and buried hill structures. A new tomographic workflow involving multiscale parameterization, grid size optimization, and initial model scanning is proposed to improve the fidelity of tomographic inversion. Numerical tests show that optimal grid selection effectively enhances inversion accuracy under large station spacing. The use of initial model scanning combined with inversion parameters optimization significantly improves the stability of the solution. The final inverted model reveals three isolated high-velocity anomalies, located at approximately 40&#xa0;km, 100&#xa0;km, and 120&#xa0;km along the profile, which are consistent with characteristics of buried hills. Those buried hills produce a basement relief of about 2&#xa0;km, which is further supported by refraction arrival-time interpretation, and distort the sedimentary layers, indicating their significance in controlling the eastern sub-basin structure. The proposed tomographic strategy offers a robust approach for constructing reliable upper crustal models from sparsely spaced OBS data.</p>

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High-fidelity upper crustal imaging beneath Gunsan Basin with a sparse OBS array and modified multiscale seismic tomographic workflow

  • 期刊论文

  • 发表日期：

    2026年4月22日

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  • Wenfa Zhou,
  • Zhihui Zou

摘要

The Gunsan Basin in the South Yellow Sea has undergone multi-phase tectonic evolution in the East Asian margin, and its basin structures are important for understanding the regional tectonic processes. Previous studies using ocean-bottom seismometer (OBS) and streamer data have revealed a complex crustal structure in this region, including the crustal thinning due to strike-slip faulting and the development of buried hills. However, the large station spacing in OBS surveys results in low resolution of tomographic inversion, leading to an ambiguity in the interpretation of basin geometry and buried hill structures. A new tomographic workflow involving multiscale parameterization, grid size optimization, and initial model scanning is proposed to improve the fidelity of tomographic inversion. Numerical tests show that optimal grid selection effectively enhances inversion accuracy under large station spacing. The use of initial model scanning combined with inversion parameters optimization significantly improves the stability of the solution. The final inverted model reveals three isolated high-velocity anomalies, located at approximately 40 km, 100 km, and 120 km along the profile, which are consistent with characteristics of buried hills. Those buried hills produce a basement relief of about 2 km, which is further supported by refraction arrival-time interpretation, and distort the sedimentary layers, indicating their significance in controlling the eastern sub-basin structure. The proposed tomographic strategy offers a robust approach for constructing reliable upper crustal models from sparsely spaced OBS data.