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<p>From October to December 2024, the level of seismicity in the Mozhugongka area, Tibetan Plateau, was extremely high. Owing to the complex geological and tectonic environment in the area, the seismogenic structure is not clear. In this study, by collecting earthquake bulletins and three-component seismic event waveforms recorded by the permanent stations of the China Seismic Network, using the double-difference relocation, the focal mechanism solution inversion and the stress field inversion, we obtain the relocation results for 1701 earthquakes and focal mechanism solutions for 19 earthquakes of <i>M</i> ≥ 3.0 to reveal and analyze the characteristics of the seismicity and the corresponding dynamic mechanisms. Our results show that the earthquake swarm is distributed in a strip with a NNE‒SSW strike, with a length of approximately 20&#xa0;km and a depth of 5–18&#xa0;km, and it has the characteristics of a shallow normal fault and deep strike-slip fault, suggesting that the earthquakes in the swarm are controlled by a concealed fault. The regional stress field is dominated by normal fault properties of almost north–south compression and almost east–west tension. However, after the <i>M</i>4.5 earthquake, the stress field changed from exhibiting the characteristics of a normal fault controlled by a shallow structure to exhibiting those of a strike-slip fault that is dominated by the deeper faults, reflecting the layered stress release caused by the oblique subduction of the Indian Plate beneath the Tibetan Plateau. The excess fluid pressure within the earthquake swarm exhibits periodic variations, suggesting that deep fluids repeatedly trigger seismic activity, likely linked to locally elevated background heat flow. The Mozhugongka earthquake swarm reflects adjustments of the local seismogenic environment of the Lhasa block in response to the India-Eurasia plate collision. These results provide new insights into the seismogenic mechanism operating on the Tibetan Plateau.</p>

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Triggering mechanisms of the 2024 M4.5 earthquake swarm in Mozhugongka, Tibetan Plateau: Constraints from seismotectonics and the role of deep fluids

  • 期刊论文

  • 发表日期：

    2026年6月29日

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  • Guoqiang Ji,
  • Xingzhong Du,
  • Yong Li,
  • Xuan Ke,
  • Xiaohui Hu,
  • Huabiao Liu,
  • Yu Tang,
  • Kairong Pi

摘要

From October to December 2024, the level of seismicity in the Mozhugongka area, Tibetan Plateau, was extremely high. Owing to the complex geological and tectonic environment in the area, the seismogenic structure is not clear. In this study, by collecting earthquake bulletins and three-component seismic event waveforms recorded by the permanent stations of the China Seismic Network, using the double-difference relocation, the focal mechanism solution inversion and the stress field inversion, we obtain the relocation results for 1701 earthquakes and focal mechanism solutions for 19 earthquakes of M ≥ 3.0 to reveal and analyze the characteristics of the seismicity and the corresponding dynamic mechanisms. Our results show that the earthquake swarm is distributed in a strip with a NNE‒SSW strike, with a length of approximately 20 km and a depth of 5–18 km, and it has the characteristics of a shallow normal fault and deep strike-slip fault, suggesting that the earthquakes in the swarm are controlled by a concealed fault. The regional stress field is dominated by normal fault properties of almost north–south compression and almost east–west tension. However, after the M4.5 earthquake, the stress field changed from exhibiting the characteristics of a normal fault controlled by a shallow structure to exhibiting those of a strike-slip fault that is dominated by the deeper faults, reflecting the layered stress release caused by the oblique subduction of the Indian Plate beneath the Tibetan Plateau. The excess fluid pressure within the earthquake swarm exhibits periodic variations, suggesting that deep fluids repeatedly trigger seismic activity, likely linked to locally elevated background heat flow. The Mozhugongka earthquake swarm reflects adjustments of the local seismogenic environment of the Lhasa block in response to the India-Eurasia plate collision. These results provide new insights into the seismogenic mechanism operating on the Tibetan Plateau.