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<p>The Mw 6.5 earthquake that struck Ambon and the Maluku region of Indonesia on 26 September 2019 caused significant damage to the surrounding populated areas. Previous studies have indicated that this earthquake was primarily generated by a North–South oriented strike-slip fault, with an estimated rupture length of approximately 35&#xa0;km. Over 1,600 aftershocks were recorded in the region between 18 October and 15 December 2019, including an Mw 5.2 earthquake on 12 November 2019. We performed a local earthquake tomography (Vp, Vs, and Vp/Vs ratio) utilizing the local network of 11 temporary and three permanent seismic stations to elucidate the structural features beneath the source region, which is essential for understanding how the Mw 6.5 earthquake sequence was generated. The presence of faults can be delineated from the lateral velocity contrasts at 5&#xa0;km depths and the relocated aftershocks, which suggest multiple interacting fault segments between seismic clusters in the west of Haruku and southwest of Seram Islands. Seismic cluster in the west of Haruku is situated in a region with slightly high Vp, high Vs, and low Vp/Vs at 5&#xa0;km depths, likely indicating the brittle sections of the fault. In contrast, the seismic cluster in the southwest of Seram Island has relatively low Vp, a range of low-to-high Vs, and a low Vp/Vs ratio at a depth of 5&#xa0;km, suggesting a partially fluid-saturated, fractured rock environment within a pre-existing hidden fault. Furthermore, the reactivation of the pre-existing fault in the eastern Ambon Island may be attributed to the presence of over-pressurized fluids within the fractured fault zone, which likely generated a Mw 5.2 earthquake on 12 November 2019 and the aftershocks cluster in the eastern Ambon Island, which is characterized by the low Vp, low Vs, and high Vp/Vs ratio.</p> Graphical Abstract <p></p>

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Seismic velocity structure beneath the source region of the 2019 Ambon earthquake (Mw 6.5), Indonesia, from local earthquake tomography

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月10日

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  • Andri Dian Nugraha,
  • Faiz Muttaqy,
  • Rexha Verdhora Ry,
  • Pepen Supendi,
  • Shindy Rosalia,
  • David P. Sahara,
  • Aria Widhi Baskara,
  • Abdul Muhari,
  • Awali Priyono,
  • Z. Zulfakriza,
  • Sri Widiyantoro,
  • Nanang T. Puspito,
  • Erfin Elly

摘要

The Mw 6.5 earthquake that struck Ambon and the Maluku region of Indonesia on 26 September 2019 caused significant damage to the surrounding populated areas. Previous studies have indicated that this earthquake was primarily generated by a North–South oriented strike-slip fault, with an estimated rupture length of approximately 35 km. Over 1,600 aftershocks were recorded in the region between 18 October and 15 December 2019, including an Mw 5.2 earthquake on 12 November 2019. We performed a local earthquake tomography (Vp, Vs, and Vp/Vs ratio) utilizing the local network of 11 temporary and three permanent seismic stations to elucidate the structural features beneath the source region, which is essential for understanding how the Mw 6.5 earthquake sequence was generated. The presence of faults can be delineated from the lateral velocity contrasts at 5 km depths and the relocated aftershocks, which suggest multiple interacting fault segments between seismic clusters in the west of Haruku and southwest of Seram Islands. Seismic cluster in the west of Haruku is situated in a region with slightly high Vp, high Vs, and low Vp/Vs at 5 km depths, likely indicating the brittle sections of the fault. In contrast, the seismic cluster in the southwest of Seram Island has relatively low Vp, a range of low-to-high Vs, and a low Vp/Vs ratio at a depth of 5 km, suggesting a partially fluid-saturated, fractured rock environment within a pre-existing hidden fault. Furthermore, the reactivation of the pre-existing fault in the eastern Ambon Island may be attributed to the presence of over-pressurized fluids within the fractured fault zone, which likely generated a Mw 5.2 earthquake on 12 November 2019 and the aftershocks cluster in the eastern Ambon Island, which is characterized by the low Vp, low Vs, and high Vp/Vs ratio.

Graphical Abstract