EGU25-5539, updated on 14 Mar 2025
https://doi.org/10.5194/egusphere-egu25-5539
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Poster | Thursday, 01 May, 10:45–12:30 (CEST), Display time Thursday, 01 May, 08:30–12:30
 
Hall X1, X1.110
New insights into fault structures of the Haichenghe Fault Zone through dense array observation
Lanshu Bai1, Qingshan Sun2, Mingruo Jiao2, Liang Wang2, Shichao Yang2, Jiuyang Wang2, Enlai Li2, and Qingju Wu1
Lanshu Bai et al.
  • 1Institute of Geophysics, China Earthquake Administration, Beijing, China (bailanshu@cea-igp.ac.cn)
  • 2Liaoning Earthquake Agency, Shenyang, China

The Haichenghe fault zone (HFZ), renowned as the site of a successfully predicted earthquake, namely the 1975 M7.3 Haicheng earthquake, as well as the 1999 M5.4 Xiuyan earthquake, is one of the most seismically active zones in eastern China. Nevertheless, fault structures within the key areas of the HFZ remain inadequately characterized, which limits the understanding of the fault behavior and seismological mechanism of the region. Consequently, from August 2021 to September 2023, we deployed the densest array to date, consisting of 23 broadband seismic stations with an average distance interval of about 6 km. Based on the dense observation data, we constructed a high-precision catalog of the HFZ utilizing neural network-based phase picking, earthquake association, and relocation methods. Our results show that:

  • The HFZ is characterized by a conjugate fault system composed of WNW-striking and NE-striking subvertical faults of different scales. The Haichenghe Fault (HF) appears as a WNW-trending en echelon fault, traversing the entire study area. The 30-kilometer-long main segment (MHF) in the northwest is responsible for the Haicheng 7.3 earthquake, while the 5-kilometer-long Xiuyan segment (XYF) in the southeast generated the Xiuyan M5.4 earthquake.
  • The MHF is further segmented into eastern and western sections. A several-kilometer-wide step-over between two sections is connected by two NE/NNE trending faults. It can be deduced that the rupture of the Haicheng earthquake along the WNW direction was not continuous throughout, but terminated or transferred to these two NE/NEE trending faults at the step-over.
  • At the intersection of the MHF and its main NE-trending conjugate fault, a horizontally asymmetric conjugate rupture area of the Haicheng M7.3 earthquake has been identified. Moreover, a vertically triangular seismic gap has been discovered, suggesting a strong heterogeneity of the subsurface medium in this region.

How to cite: Bai, L., Sun, Q., Jiao, M., Wang, L., Yang, S., Wang, J., Li, E., and Wu, Q.: New insights into fault structures of the Haichenghe Fault Zone through dense array observation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5539, https://doi.org/10.5194/egusphere-egu25-5539, 2025.