Work

Automated 3-D modelling of seismic faults using adaptive threshold hierarchical clustering and quantitative assessment

Year: 2025

Type: article

Abstract: SUMMARY The complex three-dimensional (3-D) geometry of active faults plays a crucial role in controlling earthquake location, extent, and rupture behaviour, making the accurate representation of fault models essential. Fault structures are typically interpreted manually from relocated hypocentres and interpolated to generate 3-D fault surfaces. However, this process is often non-unique and uncertain due to the uneven spatial distribution of earthquake hypocentres, the subjectivity of manual interpretation and the complexity of non-planar faults. To address these challenges, we developed a method that combines adaptive threshold hierarchical clustering with quantitative evaluation to automatically and effectively construct 3-D models of seismogenic faults. This method utilizes the nearest neighbour index (NNI) to determine whether seismic activity exhibits clustering characteristics indicative of fault structures. Adaptive threshold hierarchical clustering is subsequently applied to identify small earthquake clusters associated with each fault. High-density 3-D automatic slicing ensures robust fitting of fault lines, and in combination with surface rupture data, discrete smooth interpolation (DSI) is used to construct a 3-D fault model. For each fault, we calculate distances from small earthquake clusters to the 3-D fault structure and analyse their spatial distribution using kernel density estimation (KDE) to optimize the model for a near-symmetric distribution of small earthquake clusters on both sides of the fault. We applied this method to the 2013 Ms 7.0 and 2022 Ms 6.1 earthquakes in southern Longmenshan, Sichuan, China, refining the 3-D seismogenic fault models for both events. Additionally, we constructed a 3-D fault model for the 2019 Ridgecrest Mw 7.1 earthquake sequence using the same approach. The results indicate that this method is applicable to both individual faults and multiple intersecting fault systems. Compared to traditional manual modelling approaches, our method significantly enhances the identification of small earthquake clusters, reduces reliance on manual interpretation, increases modelling efficiency and minimizes errors. This innovative modelling technique advances the 3-D geometric construction of complex active faults and is adaptable to a wide range of seismic research applications.

Source: Geophysical Journal International

DOI: 10.1093/gji/ggaf426

Authors: Xiao Sun, Renqi Lu, Wei Wang, Fan Yang, Kefeng He

Institutions: Institute of Geology, China Earthquake Administration, State Key Laboratory of Earthquake Dynamics, China Earthquake Administration, Nantong University, Wuhan University

Language: English

Topic: earthquake and tectonic studies

Subfield: Geophysics

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,416

Funder: National Science and Technology Council